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Contents Wiring diagrams Section: Communication Devices All sections

Data Communications System Buick Regal V

Communication Devices 13 illustrations ~38398 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Body Control Module Bracket Fastener9 N.m80 lb in

Fastener Tightening Specifications

Scheme 1

Scheme 1: Low Speed GMLAN Wiring Schematics
Scheme 1: Low Speed GMLAN Wiring Schematics

Scheme 2

Scheme 2: Mid Speed GMLAN Wiring Schematics
Scheme 2: Mid Speed GMLAN Wiring Schematics

Scheme 3

Scheme 3: High Speed GMLAN (1 of 2) Wiring Schematics
Scheme 3: High Speed GMLAN (1 of 2) Wiring Schematics

Scheme 4

Scheme 4: High Speed GMLAN (2 of 2) Wiring Schematics
Scheme 4: High Speed GMLAN (2 of 2) Wiring Schematics

Scheme 5

Scheme 5: High Speed GMLAN CE Bus Wiring Schematics
Scheme 5: High Speed GMLAN CE Bus Wiring Schematics

Scheme 6

Scheme 6: Communications Enable Wiring Schematics
Scheme 6: Communications Enable Wiring Schematics

Scheme 7

Scheme 7: Linear Interconnect Network Wiring Schematics
Scheme 7: Linear Interconnect Network Wiring Schematics

Scheme 8

Scheme 8: Power, Ground and Serial Data Wiring Schematics
Scheme 8: Power, Ground and Serial Data Wiring Schematics

Scheme 9

Scheme 9: Subsytem References (1 of 3) Wiring Schematics
Scheme 9: Subsytem References (1 of 3) Wiring Schematics

Scheme 10

Scheme 10: Subsytem References (2 of 3) Wiring Schematics
Scheme 10: Subsytem References (2 of 3) Wiring Schematics

Scheme 11

Scheme 11: Subsytem References (3 of 3) Wiring Schematics
Scheme 11: Subsytem References (3 of 3) Wiring Schematics

Diagnostic Code Index

DTCDescription
Control Module U Code List
DTC B1000DTC B1000 00 Electronic Control Unit DTC B1000 08 Electronic Control Unit Performance - Signal Invalid DTC B1000 0F Electronic Control Unit Signal Erratic DTC B1000 12 Electronic Control Unit Low Input DTC B1000 2B Electronic Control Unit Missing Reference DTC B1000 34 Electronic Control Unit RAM Malfunction DTC B1000 35 Electronic Control Unit ROM Malfunction DTC B1000 36 Electronic Control Unit EEPROM Performance/Malfunction DTC B1000 37 Electronic Control Unit Software Malfunction DTC B1000 38 Electronic Control Unit Supervision Software Malfunction DTC B1000 39 Electronic Control Unit Internal Malfunction DTC B1000 43 Electronic Control Unit EEPROM Incorrect Programming DTC B1000 46 Electronic Control Unit Configuration Not Programmed DTC B1000 4A Electronic Control Unit Programming Checksum Error DTC B1000 56 Electronic Control Unit Too Many Transitions DTC B1000 73 Electronic Control Unit Parity Error DTC B1000 F0 Electronic Control Unit DTC B1000 F1 Electronic Control Unit DTC B1000 F2 Electronic Control Unit DTC B1000 F3 Electronic Control Unit
DTC B1001DTC B1001 00 Option Configuration DTC B1001 33 Option Configuration Special Memory Malfunction DTC B1001 45 Option Configuration Variant Not Programmed DTC B1001 4B Option Configuration Calibration Not Learned
DTC B101DDTC B101D 00 Electronic Control Unit Hardware DTC B101D 04 Electronic Control Unit Hardware Open DTC B101D 08 Electronic Control Unit Hardware Performance - Signal Invalid DTC B101D 0F Electronic Control Unit Hardware Signal Erratic DTC B101D 12 Electronic Control Unit Hardware Low Input DTC B101D 13 Electronic Control Unit Hardware Low Voltage/High Temperature DTC B101D 14 Electronic Control Unit Hardware High Voltage/Low Temperature DTC B101D 1A Electronic Control Unit Hardware Performance - Bias Level Out of Range DTC B101D 2B Electronic Control Unit Hardware Missing Reference DTC B101D 2C Electronic Control Unit Hardware DTC B101D 31 Electronic Control Unit Hardware Internal Checksum Error DTC B101D 32 Electronic Control Unit Hardware General Memory Malfunction DTC B101D 34 Electronic Control Unit Hardware RAM Malfunction DTC B101D 35 Electronic Control Unit Hardware ROM Malfunction DTC B101D 36 Electronic Control Unit Hardware EEPROM Performance/Malfunction DTC B101D 37 Electronic Control Unit Hardware Software Malfunction DTC B101D 38 Electronic Control Unit Hardware Supervision Software Malfunction DTC B101D 39 Electronic Control Unit Hardware Internal Malfunction DTC B101D 3A Electronic Control Unit Hardware Incorrect Component Installed DTC B101D 3B Electronic Control Unit Hardware Self-Test Malfunction DTC B101D 3C Electronic Control Unit Hardware Internal Communication Malfunction DTC B101D 43 Electronic Control Unit Hardware EEPROM Incorrect Programming DTC B101D 73 Electronic Control Unit Hardware Parity Error DTC B101D F0 Electronic Control Unit Hardware DTC B101D F1 Electronic Control Unit Hardware
DTC B101EDTC B101E 00 Electronic Control Unit Software DTC B101E 31 Electronic Control Unit Software Internal Checksum Error DTC B101E 32 Electronic Control Unit Software General Memory Malfunction DTC B101E 41 Electronic Control Unit Software Not Programmed DTC B101E 42 Electronic Control Unit Software Calibration Not Programmed DTC B101E 43 Electronic Control Unit Software EEPROM Incorrect Programming DTC B101E 44 Electronic Control Unit Software Security Access Not Activated DTC B101E 45 Electronic Control Unit Software Variant Not Programmed DTC B101E 46 Electronic Control Unit Software Configuration Not Programmed DTC B101E 47 Electronic Control Unit Software VIN Not Programmed DTC B101E 48 Electronic Control Unit Software Security Code Not Programmed DTC B101E 4A Electronic Control Unit Software Programming Checksum Error DTC B101E 4B Electronic Control Unit Software Calibration Not Learned DTC B101E 4C Electronic Control Unit Software DTC Memory Full
DTC C0550DTC C0550 00 Electronic Control Unit DTC C0550 35 Electronic Control Unit ROM Malfunction DTC C0550 39 Electronic Control Unit Internal Malfunction DTC C0550 43 Electronic Control Unit EEPROM Incorrect Programming
DTC C056DDTC C056D 00 Electronic Control Unit Hardware DTC C056D 0F Electronic Control Unit Hardware Signal Erratic DTC C056D 18 Electronic Control Unit Hardware Low Signal Amplitude DTC C056D 31 Electronic Control Unit Hardware Internal Checksum Error DTC C056D 32 Electronic Control Unit Hardware General Memory Malfunction DTC C056D 33 Electronic Control Unit Hardware Special Memory Malfunction DTC C056D 34 Electronic Control Unit Hardware RAM Malfunction DTC C056D 35 Electronic Control Unit Hardware ROM Malfunction DTC C056D 36 Electronic Control Unit Hardware EEPROM Performance/Malfunction DTC C056D 37 Electronic Control Unit Hardware Software Malfunction DTC C056D 39 Electronic Control Unit Hardware Internal Malfunction DTC C056D 3A Electronic Control Unit Hardware Incorrect Component Installed DTC C056D 3B Electronic Control Unit Hardware Self-Test Malfunction DTC C056D 3C Electronic Control Unit Hardware Internal Communication Malfunction DTC C056D 43 Electronic Control Unit Hardware EEPROM Incorrect Programming
DTC C056EDTC C056E 00 Electronic Control Unit Software DTC C056E 38 Electronic Control Unit Software Supervision Software Malfunction DTC C056E 41 Electronic Control Unit Software Not Programmed DTC C056E 42 Electronic Control Unit Software Calibration Not Programmed DTC C056E 43 Electronic Control Unit Software EEPROM Incorrect Programming DTC C056E 45 Electronic Control Unit Software Variant Not Programmed DTC C056E 46 Electronic Control Unit Software Configuration Not Programmed DTC C056E 47 Electronic Control Unit Software VIN Not Programmed DTC C056E 48 Electronic Control Unit Software Security Code Not Programmed DTC C056E 4A Electronic Control Unit Software Programming Checksum Error DTC C056E 4B Electronic Control Unit Software Calibration Not Learned DTC C056E 5A Electronic Control Unit Software Not Plausible DTC C056E 71 Electronic Control Unit Software Invalid Data
DTC C078ADTC C078A 39 Tire Pressure Indicator Module Internal Malfunction
DTC P0601-P0604, P0606, or P062FDTC P0601 00 Control Module Read Only Memory Performance DTC P0602 00 Control Module Not Programmed DTC P0603 00 Control Module Long Term Memory Reset DTC P0604 00 Control Module Random Access Memory Performance DTC P0606 00 Control Module Processor Performance DTC P062F 00 Control Module Long Term Memory Performance
DTC U0001DTC U0001 00 High Speed CAN Communication Bus
DTC U0002DTC U0002 High Speed CAN Bus
DTC U0020DTC U0020 00 Low Speed CAN Communication Bus Performance
DTC U0073 or U2100DTC U0073 00 Control Module Communication Bus Off DTC U0073 71 ECU HS Bus Off DTC U0073 72 ECU LS Bus Off DTC U2100 00 Controller Area Network (CAN) Bus Communication DTC U2100 47 Controller Area Network (CAN) Bus Communication
DTC U0074 (Mid Speed or Chassis Expansion Bus)DTC U0074 00 Control Module Communication Bus B Off
DTC U0074 (Powertrain Expansion Bus)DTC U0074 00 Control Module Communication Powertrain Expansion CAN Bus Off
DTC U0078DTC U0078 00 Control Module Low Speed Communication Bus Off
DTC U0100-U02FF (with HP6)
DTC U0100-U02FF (without HP6)
DTC U0300-U0336DTC U0301 00 Software Incompatibility with Engine Control Module DTC U0302 00 Software Incompatibility with Transmission Control Module DTC U0315 00 Software Incompatibility with Electronic Brake Control Module
DTC U0400-U05FF
DTC U1500-U15BF
DTC U180BDTC U180B 00 Battery Energy Control Module High Speed CAN Bus Off
DTC U1811DTC U1811 00 Battery Energy Control Module Powertrain Expansion CAN Bus Off
DTC U1814DTC U1814 00 Powertrain Wake Up Communication Circuit DTC U1814 01 Powertrain Wake Up Communication Circuit Short to Battery DTC U1814 02 Powertrain Wake Up Communication Circuit Short to Ground DTC U1814 04 Powertrain Wake Up Communication Circuit Open DTC U1814 5A Powertrain Wake Up Communication Circuit Not Plausible
DTC U1817DTC U1817 00 Lost Communication with Hybrid Powertrain Control Module on Powertrain Expansion CAN Bus
DTC U1818DTC U1818 00 Lost Communication with Engine Control Module on Powertrain Expansion CAN Bus
DTC U182ADTC U182A 00 Hybrid Powertrain Control Module Lost Communication with Battery Energy Control Module on Powertrain Expansion CAN Bus
DTC U1831DTC U1831 00 Drive Motor Control Module 1 Lost Communication with Hybrid Powertrain Control Module
DTC U1844DTC U1844 00 Battery Energy Control Module Lost Communication with Hybrid Powertrain Control Module on Powertrain Expansion CAN Bus
DTC U1845 or U1846DTC U1845 00 Drive Motor Control Module 1 Lost Communication with Hybrid Powertrain Control Module
DTC U1847DTC U1847 00 Drive Motor Control Module 1 Lost Communication with Battery Energy Control Module on Powertrain Expansion CAN Bus
DTC U1875DTC U1875 00 Drive Motor Control Module 1 Lost Communication with Battery Energy Control Module
DTC U1876DTC U1876 00 Drive Motor Control Module 1 Lost Communication with Engine Control Module
DTC U1885DTC U1885 00 Battery Energy Control Module Lost Communication with Hybrid Powertrain Control Module
DTC U1886DTC U1886 00 Battery Energy Control Module Lost Communication with Engine Control Module
DTC U18B9-U18BFDTC U18B9 Primary High Speed CAN Bus Subnet Configuration List DTC U18BF Secondary High Speed CAN Bus Subnet Configuration List
DTC U1901DTC U1901 00 Lost Communication With Front Controls Multifunction Interface Module
DTC U2099DTC U2099 00 High Speed Communication Enable Circuit DTC U2099 01 High Speed Communication Enable Circuit Short to Battery DTC U2099 02 High Speed Communication Enable Circuit Short to Ground DTC U2099 04 High Speed Communication Enable Circuit Open DTC U2099 5A High Speed Communication Enable Circuit Not Plausible
DTC U2101DTC U2101 CAN Bus Maximum Configuration List
DTC U2103DTC U2103 00 Fewer Controllers On Than Programmed
DTC U2105-U2199

DIAGNOSTIC CODE INDEX

Control Module U Code List

This list includes all Data Communications related U-code DTCs in alphanumeric order with descriptors for all modules. Not all DTCs listed will be applicable to all vehicles.

DTCDTC Descriptor
U0001 00High Speed CAN Bus Malfunction
U0001 04High Speed CAN Bus Malfunction Open
U0002 00High Speed CAN Bus
U0020 00Low Speed CAN Bus
U0073 00Control Module Communication Bus A Off
U0073 01Control Module Communication Bus A Off Short to Battery
U0073 02Control Module Communication Bus A Off Short to Ground
U0073 04Control Module Communication Bus A Off Open
U0073 71Control Module Communication Bus A Off Invalid Data
U0074 00Control Module Communication Bus B Off
U0077 00Control Module Chassis Expansion Communication Bus Off
U0078 00Control Module Low Speed Communication Bus Off
U007A 00Control Module High Voltage Energy Management Communication Bus Off
U0100 00Lost Communication With Engine Control Module
U0100 71Lost Communication With Engine Control Module Invalid Data
U0100 72Lost Communication With Engine Control Module Message Counter Incorrect
U0100 74Lost Communication With Engine Control Module Bus Signal Checksum Error
U0101 00Lost Communication With Transmission Control Module
U0101 71Lost Communication With Transmission Control Module Invalid Data
U0102 00Lost Communication with Transfer Case Control Module
U0102 71Lost Communication with Transfer Case Control Module Invalid Data
U0104 00Lost Communication With Cruise Control Module
U0104 02Lost Communication With Cruise Control Module Short to Ground
U0104 71Lost Communication With Cruise Control Module Invalid Data
U0104 72Lost Communication With Cruise Control Module Message Counter Incorrect
U0104 74Lost Communication With Cruise Control Module Bus Signal Checksum Error
U0105 00Lost Communication with Fuel Injector Control Module
U0109 00Lost Communication with Fuel Pump Control Module
U010F 00Lost Communication with Air Conditioning Control Module
U0111 00Lost Communication with Battery Energy Control Module
U0112 00Lost Communication with Battery Energy Control Module
U0115 00Lost Communication with ECM 2
U0117 00Lost Communication With Power Take-Off Control Module
U0121 00Lost Communication With Electronic Brake Control Module
U0121 03Lost Communication With Electronic Brake Control Module Low Voltage
U0121 71Lost Communication With Electronic Brake Control Module Invalid Data
U0121 72Lost Communication With Electronic Brake Control Module Message Counter Incorrect
U0121 74Lost Communication With Electronic Brake Control Module Bus Signal Checksum Error
U0122 00Lost Communication With Vehicle Stability Control Module
U0125 00Lost Communication With Multi-axis Acceleration Sensor Module
U0125 71Lost Communication With Multi-axis Acceleration Sensor Module Invalid Data
U0125 72Lost Communication With Multi-axis Acceleration Sensor Module Message Counter Incorrect
U0125 74Lost Communication With Multi-axis Acceleration Sensor Module Bus Signal Checksum Error
U0126 00Lost Communication With Steering Wheel Angle Sensor Module
U0126 71Lost Communication With Steering Wheel Angle Sensor Module Invalid Data
U0126 72Lost Communication With Steering Wheel Angle Sensor Module Message Counter Incorrect
U0126 74Lost Communication With Steering Wheel Angle Sensor Module Bus Signal Checksum Error
U0126 5ALost Communication With Steering Wheel Angle Sensor Module Not Plausible
U0128 00Lost Communication With Park Brake Control Module
U0128 71Lost Communication With Park Brake Control Module Invalid Data
U0128 72Lost Communication With Park Brake Control Module Message Counter Incorrect
U0128 74Lost Communication With Park Brake Control Module Bus Signal Checksum Error
U0129 00Lost Communication with Brake System Control Module
U0130 00Lost Communication With Electric Power Steering Control Module
U0130 71Lost Communication With Electric Power Steering Control Module Invalid Data
U0130 72Lost Communication With Electric Power Steering Control Module Message Counter Incorrect
U0130 74Lost Communication With Electric Power Steering Control Module Bus Signal Checksum Error
U0131 00Lost Communication With Power Steering Control Module
U0131 71Lost Communication With Power Steering Control Module Invalid Data
U0132 00Lost Communication With Suspension Control Module
U0133 00Lost Communication With Air Suspension Control Module
U0133 71Lost Communication With Air Suspension Control Module Invalid Data
U0136 00Lost Communication With Differential Control Module - Rear
U0136 71Lost Communication With Differential Control Module - Rear Invalid Data
U0139 00Lost Communication With Suspension Control Module
U0139 71Lost Communication With Suspension Control Module Invalid Data
U0140 00Lost Communication With Body Control Module
U0140 08Lost Communication With Body Control Module Performance - Signal Invalid
U0140 71Lost Communication With Body Control Module Invalid Data
U0140 72Lost Communication With Body Control Module Message Counter Incorrect
U0140 74Lost Communication With Body Control Module Bus Signal Checksum Error
U0146 00Lost Communication with Gateway
U0151 00Lost Communication With Inflatable Restraint Sensing and Diagnostic Module
U0155 00Lost Communication With Instrument Cluster
U0158 00Lost Communication With Head-Up Display
U0159 00Lost Communication With Parking Assist Control Module
U0160 00Lost Communication With Chime Alarm Control Module
U0164 00Lost Communication with HVAC Control Module
U0166 00Lost Communication with Auxiliary Heater Control Module
U0167 00Lost Communication with Immobilizer Control Module
U0168 00Lost Communication With Keyless Entry Control Module
U016B 00Lost Communication with Electric A/C Compressor Control Module
U0170 00Lost Communication With Passenger Presence Detection Sensor Module
U0181 00Lost Communication With Headlamp Leveling Control Module
U0182 00Lost Communication With Lighting Control Module - Front
U0184 00Lost Communication With Radio
U0186 00Lost Communication With Speaker Amplifier Module
U0196 00Lost Communication With Rear Audio Control Module
U0191 00Lost Communication With Television
U0193 00Lost Communication With Digital Radio Receiver Control Module
U0197 00Lost Communication With Telephone Control Module
U0198 00Lost Communication With Telematic Control Module
U0201 00Lost Communication With Transfer Case Control Module
U0203 00Lost Communication With Left Rear Door Switch Panel Control Module
U0204 00Lost Communication With Right Rear Door Switch Panel Control Module
U0207 00Lost Communication With Moveable Roof Control Module
U0208 00Lost Communication With Memory Seat Control Module
U0209 00Lost Communication With Front Seat Heating Control Module
U0210 00Lost Communication With Rear Seat Heating Control Module
U0230 00Lost Communication With Liftgate Control Module
U0232 00Lost Communication With Side-Object Detection Control Module - Left
U0233 00Lost Communication With Side-Object Detection Control Module - Right
U0236 00Lost Communication With Steering Column Lock Module
U0237 00Lost Communication With Multimedia Player Interface Module
U023A 00Lost Communication With Vehicle Direction Camera Control Module
U0249 00Lost Communication With Rear Radio Audio Control Module
U0252 00Lost Communication With Trailer Interface Control Module
U0254 00Lost Communication With Remote Start Module
U0255 00Lost Communication With Info Display Module
U0256 00Lost Communication With Infotainment Faceplate Control Module
U0257 00Lost Communication With Info Display Module/Infotainment Faceplate Control Module
U0264 00Lost Communication With Camera Module - Rear
U0284 00Lost Communication with Active Grille Air Shutter 1 Motor Module
U0285 00Lost Communication with Active Grille Air Shutter 2 Motor Module
U0293 00Lost Communication with Hybrid Powertrain Control Module
U0301 00Software Incompatibility with Engine Control Module
U0302 00Software Incompatibility with Transmission Control Module
U0315 00Software Incompatibility with Electronic Brake Control Module
U0401 00Invalid Data Received from ECM
U0401 72Invalid Data Received from ECM Message Counter Incorrect
U0401 74Invalid Data Received from ECM Bus Signal Checksum Error
U0402 72Invalid Data Received From Transmission Control Module Message Counter Incorrect
U0402 73Invalid Data Received From Transmission Control Module Parity Error
U0402 74Invalid Data Received From Transmission Control Module Bus Signal Checksum Error
U0405 00Invalid Data Received From Cruise Control Module
U0405 71Invalid Data Received From Cruise Control Module Invalid Data
U0405 72Invalid Data Received From Cruise Control Module Message Counter Incorrect
U0405 74Invalid Data Received From Cruise Control Module Bus Signal Checksum Error
U0415 00Invalid Data Received From Electronic Brake Control Module
U0415 72Invalid Data Received From Electronic Brake Control Module Message Counter Incorrect
U0415 74Invalid Data Received From Electronic Brake Control Module Bus Signal Checksum Error
U0416 00Invalid Data Received From Vehicle Dynamics Control Module
U0416 72Invalid Data Received From Vehicle Dynamics Control Module Message Counter Incorrect
U0416 74Invalid Data Received From Vehicle Dynamics Control Module Bus Signal Checksum Error
U0418 00Invalid Data Received From Brake System Control Module
U0418 71Invalid Data Received From Brake System Control Module Invalid Data
U0418 72Invalid Data Received From Brake System Control Module Message Counter Incorrect
U0418 74Invalid Data Received From Brake System Control Module Bus Signal Checksum Error
U0422 00Invalid Data Received From Body Control Module
U0422 70Invalid Data Received From Body Control Module
U0422 72Invalid Data Received From Body Control Module Message Counter Incorrect
U0422 74Invalid Data Received From Body Control Module Bus Signal Checksum Error
U0424 00Invalid Data Received From HVAC Control Module
U0432 00Invalid Data Received From Multi-axis Acceleration Sensor Module
U0432 72Invalid Data Received From Multi-axis Acceleration Sensor Module Message Counter Incorrect
U0432 74Invalid Data Received From Multi-axis Acceleration Sensor Module Bus Signal Checksum Error
U0438 71Invalid Data Received From Trailer Brake Control Module
U0465 00Invalid Data Received From Power Take-Off Control Module
U1501 00LIN Bus 1
U1502 00LIN Bus 2
U1510 00(K9 Body Control Module) LIN Bus 1 Lost Communication With Device 0 (B67 Ultrasonic Intrusion Sensor)
(K33 HVAC Control Module) LIN Bus 1 Lost Communication With Device 0 (A26 HVAC Control)
(A11 Radio) LIN Bus 1 Lost Communication with Device 0 (A20 Radio/HVAC Control)
U1511 00(K26 Headlamp Control Module) LIN Bus 1 Lost Communication With Device 1 (E13L Headlamp Assembly-Left)
U1512 00(K26 Headlamp Control Module) LIN Bus 1 Lost Communication With Device 2 (E13R Headlamp Assembly-Right)
U1513 00(K26 Headlamp Control Module) LIN Bus 1 Lost Communication With Device 3 (E13L Headlamp Assembly-Left)
U1514 00(K26 Headlamp Control Module) LIN Bus 1 Lost Communication With Device 4 (E13R Headlamp Assembly-Right)
U1515 00(K9 Body Control Module) LIN Bus 1 Lost Communication With Device 5 (M75 Windshield Wiper Motor)
U1516 00(K9 Body Control Module) LIN Bus 1 Lost Communication With Device 6 (B110 Battery Sensor Module)
U1517 00(K9 Body Control Module) LIN Bus 1 Lost Communication With Device 7 (Sunroof Sunshade Module)
U1519 00(K40 Seat Memory Control Module) LIN Bus 1 Lost Communication With Device 9 (S52 Outside Rearview Mirror Switch)
(K40 Seat Memory Control Module) LIN Bus 1 Lost Communication With Device 9 (K96 Mirror Control Module)
U151A 00(K9 Body Control Module) LIN Bus 1 Lost Communication With Device 10 (B117 Windshield Outside Moisture Sensor)
U151B 00(K9 Body Control Module) LIN Bus 1 Lost Communication With Device 11 (K61 Sunroof Control Module)
(K40 Seat Memory Control Module) LIN Bus 1 Lost Communication With Device 11 (S79P Window Switch - Passenger)
U1520 00(K9 Body Control Module) LIN Bus 2 Lost Communication With Device 0 (P25 Power Sounder Content Theft Deterrent Alarm Module)
U1521 00(K26 Headlamp Control Module) LIN Bus 2 Lost Communication With Device 1 (E13L Headlamp Assembly-Left)
U1522 00(K9 Body Control Module) LIN Bus 2 Lost Communication With Device 2 (K65 Tire Pressure Indicator Module)
(K26 Headlamp Control Module) LIN Bus 2 Lost Communication With Device 2 (E13R Headlamp Assembly-Right)
U1523 00(K26 Headlamp Control Module) LIN Bus 2 Lost Communication With Device 3 (E13L Headlamp Assembly-Left)
U1524 00(K9 Body Control Module) LIN Bus 2 Lost Communication With Device 4 (Front Seat Heating Control Module)
(K26 Headlamp Control Module) LIN Bus 2 Lost Communication With Device 4 (E13R Headlamp Assembly-Right)
U1526 00(K9 Body Control Module) LIN Bus 2 Lost Communication With Device 6 (Rear Seat Heating Control Module)
U152C 00(K9 Body Control Module) LIN Bus 2 Lost Communication With Device 12 (K18 Electronic Compass Module)
U152D 00(K9 Body Control Module) LIN Bus 2 Lost Communication With Device 13 (S3 Automatic Gearbox Change Lever)
U1530 00(K9 Body Control Module) LIN Bus 3 Lost Communication With Device 0 (M74P Window Motor - Passenger)
U1534 00(K9 Body Control Module) LIN Bus 3 Lost Communication With Device 4 (M74D Window Motor - Driver)
U1538 00(K9 Body Control Module) LIN Bus 3 Lost Communication With Device 8 (S79D Window Switch - Driver)
U153A 00(K9 Body Control Module) LIN Bus 3 Lost Communication With Device 10 (S79P Window Switch - Passenger)
U1540 00(K9 Body Control Module) LIN Bus 4 Lost Communication With Device 0 (M74RR Window Motor - Right Rear)
U1544 00(K9 Body Control Module) LIN Bus 4 Lost Communication With Device 4 (M74LR Window Motor - Left Rear)
U1548 00(K9 Body Control Module) LIN Bus 4 Lost Communication With Device 8 (S79LR Window Switch - Left Rear)
U154A 00(K9 Body Control Module) LIN Bus 4 Lost Communication With Device 10 (S79RR Window Switch - Right Rear)
U154B 00(K9 Body Control Module) LIN Bus 4 Lost Communication With Device 11 (K49 Rear Seat Control Module)
U1793 0014V Power Module Lost Communication with Hybrid Powertrain Control Module on Powertrain Expansion Communication Bus
U1795 0014V Power Module Powertrain Expansion Communication Bus Off
U179A 00Lost Communication with Hybrid Powertrain Control Module 2
U1803 00Lost Communication with Hybrid Powertrain Control Module 2
U1806 00Battery Energy Control Module High Voltage Energy Management Communication Bus Off
U1807 00Battery Charger Control Module High Voltage Energy Management Communication Bus Off
U180A 00Electric A/C Compressor Control Module High Speed Communication Bus Off
U180B 00Battery Energy Control Module High Speed Communication Bus Off
U180C 00Battery Charger Control Module High Speed Communication Bus Off
U180D 00Electronic Brake Control Module Chassis Expansion Communication Bus Off
U1811 00Battery Energy Control Module Powertrain Expansion CAN Bus Off
U1814 01Powertrain Wake Up Communication Circuit Short to Battery
U1814 02Powertrain Wake Up Communication Circuit Short to Ground
U1814 04Powertrain Wake Up Communication Circuit Open
U1815 00Lost Communication with Drive Motor Control Module A on Powertrain Expansion Communication Bus
U1816 00Lost Communication with Drive Motor Control Module B on Powertrain Expansion Communication Bus
U1817 00Lost Communication with Hybrid Powertrain Control Module on Powertrain Expansion Communication Bus
U1818 00Lost Communication with Engine Control Module on Powertrain Expansion Communication Bus
U1821 00Lost Communication with 14V Power Module on Powertrain Expansion Communication Bus
U1826 00Lost Communication With Multi-Axis Acceleration Sensor Module on Bus B (Chassis Expansion Bus)
U1827 00Lost Communication With Steering Angle Sensor Module on Bus B (Chassis Expansion Bus)
U182D 00Lost Communication with Hybrid Powertrain Control Module 2 on Powertrain Expansion Communication Bus
U182E 00Drive Motor Control Module 1 Lost Communication with Hybrid Powertrain Control Module 2 on Powertrain Expansion Communication Bus
U182F 00Drive Motor Control Module 2 Lost Communication with Hybrid Powertrain Control Module 2 on Powertrain Expansion Communication Bus
U1831 00Drive Motor Control Module A Lost Communication with Hybrid Powertrain Control Module on Powertrain Expansion CAN Bus
U1833 00Lost Communication with Electronic Brake Control Module on Chassis Expansion Communication Bus
U1838 00Lost Communication with Battery Charger Control Module on High Voltage Energy Management Communication Bus
U1839 00Auxiliary Transmission Fluid Pump Control Module Lost Communication with Engine Control Module
U183A 00Lost Communication with OnStar Module
U183B 00Auxiliary Transmission Fluid Pump Control Module Lost Communication with Transmission Control Module
U183C 00Auxiliary Transmission Fluid Pump Control Module Lost Communication with Hybrid Powertrain Control Module 2 on Powertrain Expansion Communication Bus
U183E 00Lost Communication with OnStar Module on Low Speed Communication Bus
U1844 00Battery Energy Control Module Lost Communication with Hybrid Powertrain Control Module on Powertrain Expansion Communication Bus
U1845 00Drive Motor Control Module 1 Lost Communication with Hybrid Powertrain Control Module
U1846 00Drive Motor Control Module 2 Lost Communication with Hybrid Powertrain Control Module
U1849 00Drive Motor Control Module 1 Lost Communication with Transmission Control Module
U184B 00Lost Communication with Electronic Climate Control Module on Low Speed Communication Bus
U184C 00Lost Communication with Instrument Cluster on Low Speed Communication Bus
U184D 00Lost Communication with Radio on Low Speed Communication Bus
U184E 00Lost Communication with Inflatable Restraint Sensing and Diagnostic Module on Low Speed Communication Bus
U184F 00Electric A/C Compressor Control Module Lost Communication with Engine Control Module
U1850 00Drive Motor Control Module 2 Lost Communication with Transmission Control Module
U1858 00Electronic Brake Control Module Lost Communication with Hybrid Powertrain Control Module on Chassis Expansion Communication Bus
U185A 00Lost Communication with Battery Energy Control Module on High Voltage Energy Management Communication Bus
U185B 00Battery Energy Control Module Lost Communication with Hybrid Powertrain Control Module 2 on High Voltage Energy Management Communication Bus
U185C 00Battery Charger Control Module Lost Communication with Hybrid Powertrain Control Module 2 on High Voltage Energy Management Communication Bus
U185D 00Fuel Injector Control Module Lost Communication with Engine Control Module
U185E 00Fuel Injector Control Module Lost Communication with Body Control Module
U1860 00Electric A/C Compressor Control Module Lost Communication with Hybrid Powertrain Control Module 2
U1861 00Battery Charger Control Module Lost Communication with Engine Control Module
U186A 00Electronic Brake Control Module Lost Communication with Engine Control Module
U186A 00Electronic Brake Control Module Lost Communication with Transmission Control Module
U1876 00Drive Motor Control Module 1 Lost Communication with Engine Control Module
U1879 00Drive Motor Control Module 2 Lost Communication with Engine Control Module
U1885 00Battery Energy Control Module Lost Communication with Hybrid Powertrain Control Module
U1886 00Battery Energy Control Module Lost Communication with Engine Control Module
U1888 00Hybrid Powertrain Control Module Lost Communication with Battery Energy Control Module
U18B9 00Primary High Speed CAN Bus Subnet Configuration List
U18BF 00Secondary High Speed CAN Bus Subnet Configuration List
U1900 00Lost Communication With Speech to Text Interface Module
U1901 00Lost Communication With Front Controls Multifunction Interface Module
U2099 00High Speed Communication Enable Circuit
U2099 01High Speed Communication Enable Circuit Short to Battery
U2099 02High Speed Communication Enable Circuit Short to Ground
U2099 04High Speed Communication Enable Circuit Open
U2099 5AHigh Speed Communication Enable Circuit Not Plausible
U2100 00CAN Bus Communication
U2101 00CAN Bus Maximum Configuration List
U2103 00Fewer Controllers On Bus Than Programmed
U2105 00Lost Communication with Engine Control Module
U2106 00Lost Communication with Transmission Control Module
U2107 00Lost Communication with Body Control Module
U2108 00Lost Communication with Electronic Brake Control Module
U2127 00Lost Communication with Front HVAC Control Module
U2139 00Lost Communication with Column Integrated Module
U2144 00Lost Communication with Distance Sensing Cruise Control Module
U2176 00Lost Communication with Power Take-Off Control Module
U2178 00Lost Communication With Trailer Interface Control Module
U2400 00Fuel Injector Control Module High Speed CAN Bus Off
U2401 00Battery Energy Control Module Dedicated Bus 1 Off
U2602 00Battery Energy Control Module Lost Communication with Hybrid Powertrain Control Module 2
U2603 00Battery Energy Control Module Lost Communication with Hybrid Battery Interface Control Module 1
U2604 00Battery Energy Control Module Lost Communication with Hybrid Battery Interface Control Module 2
U2605 00Battery Energy Control Module Lost Communication with Hybrid Battery Interface Control Module 3
U2606 00Battery Energy Control Module Lost Communication with Hybrid Battery Interface Control Module 4
U2608 00Electric A/C Compressor Control Module Lost Communication with Hybrid Powertrain Control Module
U2609 00Battery Charger Control Module Lost Communication with Hybrid Powertrain Control Module
U2611 00Auxiliary Transmission Fluid Pump Control Module Lost Communication with Hybrid Powertrain Control Module
U2612 00Battery Charger Control Module Lost Communication with Hybrid Powertrain Control Module 2

Control Module U Code List

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit/System Description

The internal fault detection is handled inside the control module. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

Conditions for Running the DTC

The module runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

Conditions for Setting the DTC

The module has detected an internal malfunction.

Action Taken When the DTC Sets

The module refuses all additional inputs.

Conditions for Clearing the DTC

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Diagnostic Aids

  1. This DTC may be stored as a history DTC without affecting the operation of the module.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
  3. If this DTC is retrieved as both a current and history DTC, replace the module that set the DTC.

Circuit/System Verification

If this DTC is retrieved as a current DTC, replace the module that set the DTC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Some control modules must be configured with serial numbers, vehicle options, or other information. If a control module was not properly configured after installation that module may set DTC B1001. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

Battery voltage is between 9-16 V and data link communications operate normally.

The control module is not configured properly.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify DTC B1001 is not set.

  1. If the DTC is set, program the control module. If the DTC resets, replace the control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The internal fault detection is handled inside the control module. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

  1. The control module runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.
  2. The keyless entry control module will set this DTC with symptom byte 39 when the keyless entry control module antenna is activated.

The control module has detected an internal malfunction.

The control module refuses all additional inputs.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. If DTC B101D is set as history or current in the K36 Inflatable Restraint Sensing and Diagnostic Module (SDM) and there are Air Bag or Pretensioner DTC's with symptom byte 02, it is important to repair the deployment loop issue first prior to replacing the K36 SDM. Failure to repair the Air Bag or Pretensioner wiring concern first may cause B101D to reset in the replacement K36 SDM.
  2. This DTC may be stored as a history DTC without affecting the operation of the control module.
  3. Do not replace a control module based only on DTC B101D being set in history with the exception of the following control modules: K36 SDM K85 Passenger Presence Detection Module
  4. If DTC B101D is set as current, replace the appropriate control module.

Verify that DTC B101D is not set.

  1. If the DTC is set in the K36 SDM along with DTC B0012, B0013, B0014, B0015, B0016, B0019, B001A, B001B, B0020, B0021, B0022, B0023, B0031, or B0038, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) to diagnose those codes first.
  2. If the DTC is set with symptom byte 43, program the control module that set the DTC. If the DTC resets, replace the control module that set the DTC.
  3. If the DTC is set with other symptom bytes, replace the control module that set the DTC.

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Some control modules must be configured with specific software, serial numbers, vehicle options, or other information. If a control module was not properly configured after installation that module may set DTC B101E. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

Battery voltage is between 9-16 V and data link communications operate normally.

The control module is not configured properly.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify DTC B101E is not set.

  1. If the DTC is set, program the control module. If the DTC resets, replace the control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The internal fault detection is handled inside the control module. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

The module runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

The module has detected an internal malfunction.

The module refuses all additional inputs.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. This DTC may be stored as a history DTC without affecting the operation of the module.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
  3. If this DTC is retrieved as both a current and history DTC, replace the module that set the DTC.
  1. Verify that DTC B1325, B1330, B1370, B1380, B1424, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  2. Verify that DTC C0550 is not set. If the DTC is set with symptom byte 39 or 43, program the control module that set the DTC. If the DTC resets, replace the control module that set the DTC. If the DTC is set with other symptom bytes, replace the control module that set the DTC.

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The internal fault detection is handled inside the control module. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

The module runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

The module has detected an internal malfunction.

The module refuses all additional inputs.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. This DTC may be stored as a history DTC without affecting the operation of the module.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
  3. If this DTC is retrieved as both a current and history DTC, replace the module that set the DTC.

Verify that DTC C056D is not set.

  1. If the DTC is set in a control module that can be programmed, program the control module. If the DTC resets, replace the control module that set the DTC.
  2. If the DTC is set in a control module that can not be programmed, replace the control module that set the DTC.
  3. If the DTC is set in a sensor, replace the sensor that set the DTC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for module replacement, programming and setup

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Some control modules must be configured with specific software, serial numbers, vehicle options, or other information. If a control module was not properly configured after installation that module may set DTC C056E. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

Battery voltage is between 9-16 V and data link communications operate normally.

The control module is not configured properly.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify DTC C056E is not set.

  1. If the DTC is set in a control module, program the control module. If the DTC resets, replace the control module that set the DTC.
  2. If the DTC is set in a sensor, program the sensor. If the DTC resets, replace the sensor that set the DTC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The internal fault detection is handled inside the tire pressure indicator module. No external circuit diagnosis is involved.

The control module runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

The control module has detected an internal malfunction.

The control module refuses all additional inputs.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. This DTC may be stored as a history DTC without affecting the operation of the control module.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the control module.
  3. If this DTC is retrieved as both a current and history DTC, replace the tire pressure indicator module.

Verify that DTC C078A is not set.

  1. If the DTC is set, replace the K65 tire pressure indicator module.

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

This diagnostic applies to internal microprocessor integrity conditions within the control module. This diagnostic also addresses if the control module is not programmed. The control module monitors its ability to read and write to the memory. It also monitors a timing function. No external circuits are involved.

  1. The ignition is ON.
  2. The system voltage is greater than 9.5 V.

The control module detects an internal malfunction or incomplete programming.

DTCs P0601, P0602, P0603, P0604, P0606, and P062F are Type A DTCs.

DTCs P0601, P0602, P0603, P0604, P0606, and P062F are Type A DTCs.

If stored only as a history DTC and not retrieved as a current DTC, do not replace the control module.

  1. Verify that DTC P0602 is not set. If the DTC P0602 is set, program the control module that set the DTC. If the DTC P0602 resets, replace the control module that set the DTC.
  2. Verify that DTC P0601, P0603, P0604, P0606, or P062F is not set. If any of the DTCs are set, replace the control module that set the DTC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, programming and setup

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit Description

Modules connected to the GMLAN serial data circuits monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. Each module on GMLAN network maintains a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages. If the TEC value exceeds 255 the controller removes itself from the network and a DTC U0001 will be set.

  1. Voltage supplied to the module is in the normal operating voltage range.
  2. The vehicle power mode requires serial data communication to occur.

A certain number of no valid transmitted messages on the GMLAN serial data circuits are detected by the module.

  1. The module suspends all message transmission.
  2. The module uses default values for all parameters received on the GMLAN serial data circuits.
  3. The module inhibits the setting of all other GMLAN communication DTCs.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
  1. This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with GMLAN Device. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with GMLAN Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Control modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module.

  1. Voltage supplied to the modules is in the normal operating voltage range.
  2. The vehicle power mode requires serial data communication to occur.
  3. The DTC U0001 does not have a current status.

A supervised periodic message that includes the transmitter module availability has not been received.

The control module uses a default value for the missing parameter.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

With a scan tool, attempt to communicate with all control modules.

Circuit/System Testing

  1. With a scan tool, verify DTC U0100-U02FF or U2105-U2199 is not set as current. If DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , or «DTC U2105-U2199»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Ignition OFF, disconnect the applicable control module harness connector.
  3. Ignition OFF, test for less than 5 ohms between the applicable control module ground circuit and ground. If greater than the specified range, test the circuit for an open/high resistance.
  4. Ignition ON, verify a test lamp illuminates between the following circuits of the applicable control module and ground: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage supply circuits If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuit fuse is open, test the circuit for a short to ground. If the circuit tests normal, replace the applicable control module.
  5. Ignition OFF, test for less than 5 ohms between the non-communicating control module GMLAN serial data circuits and the control module reporting DTC U0002. If greater than the specified range, test the circuit for an open/high resistance.
  6. If all circuits test normal, replace the applicable control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, setup, and programming.
  2. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Modules connected to the GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have programmed information about what messages are needed to be exchanged on the serial data circuits. The messages are also supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module.

DTC U0020 will set when fewer modules are detected on the bus before the modules can learn the other modules IDs. If the communication bus is opened, or if the modules power supply is lost when the vehicle is in the OFF power mode, and then placed in the RUN power mode, U0020 will set in specific modules.

Conditions for Running the DTCs

  1. Voltage at the modules is in the normal operating voltage range.
  2. The vehicle power mode requires serial data communication to occur.
  3. The DTC U2100 does not have a current status.

A supervised periodic message that includes the transmitter module availability has not been received.

Action Taken When the DTCs Sets

The module uses a default value for the missing parameter.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnosis of this DTC is accomplished via the symptom or an additional DTC, Refer to Symptoms - Data Communications , DTC U0100-U02FF (without HP6) , DTC U0100-U02FF (with HP6) .

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The serial data circuits are serial data buses are used to communicate information between the control modules. The serial data circuits also connect directly to the data link connector (DLC).

  1. Supply voltage at the control modules is in the normal operating range.
  2. The vehicle power mode requires serial data communications.

The control module setting the DTC has attempted to establish communications on the serial data circuits more than 3 times in 5 seconds.

  1. The control module suspends all message transmission.
  2. The control module uses default values for all parameters received on the serial data circuits.
  3. In the TCM, DTC U0073 will cause the transmission to go into default gears.
  4. In the ECM and TCM, DTC U0073 will cause the malfunction indicator lamp (MIL) to illuminate.
  5. If equipped with eAssist, DTC U0073 in the hybrid powertrain control module is a type B code and will cause the malfunction indicator lamp to illuminate and result in the engine operating in conventional engine mode and will maintain 14 V module operation.
  6. The control module inhibits the setting of all other communication DTCs.
  1. The ECM/TCM modules turn off the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
  2. If equipped with eAssist, the hybrid powertrain control module turns off the MIL after the diagnostic runs and does not fail during subsequent ignition cycles. Normal operation will resume 5 seconds after subsequent ignition cycle.
  3. A current DTC clears when the malfunction is no longer present.
  4. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine which serial data system is used for a specific control module.
  2. This DTC cannot be retrieved with a current status. Diagnosis is accomplished using the symptom. Refer to «Symptoms - Data Communications»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__symptoms-data-communications) .
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Battery Positive Voltage (B+)11
Ground (DLC, terminal 5)1
Mid Speed GMLAN Serial Data (+)1U0074, 3*1
Mid Speed GMLAN Serial Data (-)1U0074, 3*1
Chassis High Speed GMLAN Serial Data (+)2U0074, 3*U0074, 2
Chassis High Speed GMLAN Serial Data (-)2U0074, 3*U0074, 2
* An open between the data link connector (DLC) and the first splice will only effect the communication with the scan tool. The vehicle control modules will still communicate. 1. No communication on any mid speed GMLAN module. 2. No communication on any chassis high speed GMLAN module. 3. An open in only one mid speed or chassis high speed GMLAN serial data circuit may allow degraded communication between the control modules.

Control modules connected to the mid speed or chassis high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules when the ignition switch is in any position other than OFF. The mid speed or chassis high speed GMLAN serial data bus uses a terminating resistor that is in parallel with the mid speed or chassis high speed GMLAN (+) and (-) circuits.

The system voltage is between 9-16 V.

A supervised periodic message that includes the transmitter module availability has not been received.

Specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Use the «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to identify the mid speed or chassis high speed GMLAN serial data modules.
  2. Some control modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no control module output voltage circuit is shorted to ground before replacing the control module.
  3. An open in the DLC ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not communicate with the vehicle.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify there are no other U code DTCs set. If other U code DTCs are set, diagnose them first. Refer to «Control Module U Code List»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__control-module-u-code-list) .
  2. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine if the control module setting DTC U0074 is on the mid speed or chassis high speed serial data circuits.

Note. Each control module may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following: Control modules the vehicle is equipped with Mid speed or chassis high speed serial data circuit terminating resistors Control module locations on the serial data circuits Each control module's mid speed or chassis high speed serial data circuit terminals

  1. Attempt to communicate with all control modules on the mid speed or chassis high speed serial data circuit. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) . Communications should not be available with two or more control modules on the mid speed or chassis high speed serial data circuit. If only one control module is not communicating, diagnose that control module only. Refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Disconnect the scan tool from the X84 DLC. The following tests will be done at the X84 DLC connector.
  3. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuits listed below and ground: Mid speed GMLAN serial data terminal 3 Mid speed GMLAN serial data terminal 11 Chassis high speed GMLAN serial data terminal 12 Chassis high speed GMLAN serial data terminal 13 If greater than the specified range, test the serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to Voltage.
  5. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 100 ohms between each serial data circuit listed below and ground: Mid speed GMLAN serial data terminal 3 Mid speed GMLAN serial data terminal 11 Chassis high speed GMLAN serial data terminal 12 Chassis high speed GMLAN serial data terminal 13 If less than the specified range, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to Ground.
  6. Test for 50-70 ohms between the serial data circuits listed below: Mid speed GMLAN serial data circuits terminal 3 and terminal 11 Chassis high speed GMLAN serial data circuits terminal 12 and terminal 13 If less than 35 ohms, test for a short between the serial data circuits. Refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance. Refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, test the serial data circuits between the DLC and the first connection to the serial data circuit for an open/high resistance.
  7. If the circuits test normal, refer to Testing the Ignition Circuit.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control module.
  2. Ignition ON, test for greater than 4.5 V between the serial data circuits and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was disconnected.
  3. Ignition OFF, disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the direction of the circuit shorted to voltage.
  4. Ignition ON, test for greater than 4.5 V between the serial data circuits and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to voltage on the serial data circuit between 2 control modules A short to voltage on the serial data circuit between a control module and a terminating resistor

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control module.
  2. Test for less than 100 ohms between each serial data circuit and ground. Verify that one or more serial data circuits are less than 100 ohms. If all serial data circuits are greater than the specified range, replace the control module that was disconnected.
  3. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the direction of the circuit shorted to ground.
  4. Test for less than 100 ohms between each serial data circuit and ground. Verify that one or more serial data circuits are less than 100 ohms. If all serial data circuits are greater than the specified range, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to ground on the serial data circuit between 2 control modules A short to ground on the serial data circuit between a control module and a terminating resistor

Testing the Serial Data Circuits for a Short between the Circuits

  1. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control module, that is not communicating.
  2. Test for less than 110 ohms between each pair of serial data circuits. Verify that one pair of serial data circuits are less than 110 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the direction of the circuits shorted together.
  5. Test for less than 110 ohms between each pair of serial data circuits. Verify that one pair of serial data circuits are less than 110 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: Serial data circuits shorted together between 2 control modules Serial data circuits shorted together between a control module and a terminating resistor A shorted terminating resistor

Testing the Serial Data Circuits for a Open/High Resistance

  1. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control module, that is not communicating.
  2. Test for greater than 130 ohms between each pair of serial data circuits. Verify that one pair of serial data circuits are greater than 130 ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the direction of the open circuit.
  5. Test for greater than 130 ohms between each pair of serial data circuits. Verify that one pair of serial data circuits are greater than 130 ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: An open/high resistance on the serial data circuit between 2 control modules An open/high resistance on the serial data circuit between a control module and a terminating resistor An open/high resistance terminating resistor

Testing the Ignition Circuit

  1. Ignition OFF, disconnect the harness connectors with the ignition circuits at an easily accessible control module that is not communicating.
  2. Ignition OFF, verify that a test lamp does not illuminate between each ignition circuit terminal and ground, at the control module connector that was just disconnected. If the test lamp does illuminate, test the ignition circuit for a short to voltage. If the circuits test normal, replace the control module that was just disconnected.
  3. Ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the control module that was just disconnected.
  4. Ignition OFF, connect the harness connectors at the control module that was just disconnected.
  5. Repeat step 1 at another control module until a short to voltage, a short to ground, or an open/high resistance is found on the ignition circuits.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Powertrain High Speed GMLAN Serial Data (+)U0074U0074U0074
Powertrain High Speed GMLAN Serial Data (-)U0074U0074U0074

The serial data is transmitted on two twisted wires that allow speeds up to 500 Kb/s. The twisted pair is terminated with two 120 ohms resistors, which can be a separate resistor in a connector assembly or internal to a control module. The resistors are used as the load for the Powertrain high speed GMLAN bus during normal vehicle operation. The Powertrain high speed GMLAN is a differential bus. The Powertrain high speed GMLAN serial data bus (+) and Powertrain high speed GMLAN serial data (-) are driven to opposite extremes from a rest or idle level of approximately 2.5 V. Driving the lines to their extremes, adds 1 V to the Powertrain high speed GMLAN serial data bus (+) circuit and subtracts 1 V from the Powertrain high speed GMLAN serial data bus (-) circuit. If serial data is lost, control modules will set a no communication code against the non-communicating control module. Note that a loss of serial data DTC does not represent a failure of the control module that set it.

  1. The system voltage is greater than 9.5 V.
  2. The vehicle power mode requires serial data communications.

A supervised periodic message that includes the transmitter module availability has not been received for more than 450 ms.

  1. DTC U0074 is a type B DTC.
  2. DTC U0074 in the hybrid powertrain control module will cause the malfunction indicator lamp (MIL) to illuminate and result in the engine operating in conventional engine mode and will maintain 14 V module operation.
  1. DTC U0074 is a type B DTC.
  2. The hybrid powertrain control module turns off the MIL after the diagnostic runs and does not fail during subsequent ignition cycles. Normal operation will resume 5 seconds after subsequent ignition cycle.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of-communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. Do not replace a control module reporting a U code. The U code identifies which control module needs to be diagnosed for a communication issue.
  3. Use the «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to identify control modules connected to the powertrain high speed GMLAN serial data circuits.
  4. Some control modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no control module output voltage circuit is shorted to ground before replacing the control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Verify that DTC P0606 is not set.

  1. If the DTC is set, refer to «DTC P0601-P0604, P0606, or P062F»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.

Note. Each control module may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following: Control modules the vehicle is equipped with Powertrain high speed GMLAN serial data circuit terminating resistors Control module locations on the Powertrain high speed GMLAN serial data circuits Each control module's ground, B+, ignition, and Powertrain high speed GMLAN serial data circuit terminals

  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the harness connectors with the Powertrain high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
  4. Ignition ON, test for less than 4.5 V between each Powertrain high speed GMLAN serial data circuit at the control module that was just disconnected and ground. If one or more Powertrain high speed GMLAN serial data circuits are greater than the specified range, test the Powertrain high speed GMLAN serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to Voltage.
  5. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 100 ohms between each Powertrain high speed GMLAN serial data circuit at the control module connector that was just disconnected and ground. If one or more Powertrain high speed GMLAN serial data circuits are less than the specified value, test the Powertrain high speed GMLAN serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to Ground.
  6. Test for 110-130 ohms between the Powertrain high speed GMLAN serial data circuits at the control module that was just disconnected. If less than 110 ohms, test for a short between the Powertrain high speed GMLAN serial data circuits. Refer to Testing the Serial Data Circuits for a Short Between The Circuits. If greater than 130 ohms but less than infinite, test the Powertrain high speed GMLAN serial data circuit for an open/high resistance. Refer to Testing the Serial Data Circuits for an Open/High Resistance.
  7. Refer to Testing the Control Module Circuits.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the Powertrain high speed GMLAN serial data circuits at another control module that is not communicating, in the direction of the circuit shorted to voltage.
  2. Ignition ON, test for greater than 4.5 V between each Powertrain high speed GMLAN serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more Powertrain high speed GMLAN serial data circuits are greater than 4.5 V. If all Powertrain high speed GMLAN serial data circuits are less than the specified range, replace the control module that was just disconnected.
  3. Repeat step 1 until one of the follow conditions are isolated: A short to voltage on the Powertrain high speed GMLAN serial data circuit between 2 control modules or splice packs, if equipped. A short to voltage on the Powertrain high speed GMLAN serial data circuit between a control module and a terminating resistor.

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the harness connectors with the Powertrain high speed GMLAN serial data circuits at another control module that is not communicating, in the direction of the circuit shorted to ground.
  2. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 1k ohms between each Powertrain high speed GMLAN serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more Powertrain high speed GMLAN serial data circuits are less than 1k ohms. If all Powertrain high speed GMLAN serial data circuits are greater than the specified range, replace the control module that was just disconnected.
  3. Repeat step 1 until one of the follow conditions are isolated: A short to ground on the Powertrain high speed GMLAN serial data circuit between 2 control modules or splice packs, if equipped. A short to ground on the Powertrain high speed GMLAN serial data circuit between a control module and a terminating resistor.

Testing the Serial Data Circuits for a Short Between The Circuits

  1. Connect the harness connectors at the control module that was previously disconnected.
  2. Ignition OFF, disconnect the harness connectors with the Powertrain high speed GMLAN serial data circuits at another control module that is not communicating, in the direction of the circuits shorted together.
  3. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 ohms between each pair of Powertrain high speed GMLAN serial data circuits at the control module connector that was just disconnected. Verify that one pair of Powertrain high speed GMLAN serial data circuits are less than 110 ohms. If each pair of Powertrain high speed GMLAN serial data circuits is greater than the specified range, replace the control module that was just disconnected.
  4. Repeat step 1 until one of the following conditions are isolated: Powertrain high speed GMLAN serial data circuits shorted together between 2 control modules or splice packs, if equipped Powertrain high speed GMLAN serial data circuits shorted together between a control module and a terminating resistor A shorted terminating resistor

Testing the Serial Data Circuits for an Open/High Resistance

  1. Connect the harness connectors at the control module that was previously disconnected.
  2. Ignition OFF, disconnect the harness connectors with the Powertrain high speed GMLAN serial data circuits at another control module that is not communicating, in the direction of the open circuit.
  3. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 130 ohms between each pair of Powertrain high speed GMLAN serial data circuits at the control module connector that was just disconnected. Verify that one pair of Powertrain high speed GMLAN serial data circuits are greater than 130 ohms. If each pair of Powertrain high speed GMLAN serial data circuits is less than the specified range, replace the control module that was just disconnected.
  4. Repeat step 1 until one of the following conditions are isolated: An open/high resistance on the Powertrain high speed GMLAN serial data circuit between 2 control modules or splice packs, if equipped An open/high resistance on the Powertrain high speed GMLAN serial data circuit between a control module and a terminating resistor An open/high resistance terminating resistor

Testing the Control Module Circuits

  1. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohms between each ground circuit terminal at the control module that was just disconnected and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  2. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The low speed GMLAN serial data bus is used to communicate information between the devices. The serial data is transmitted over a single wire to the appropriate devices. The low speed GMLAN serial data circuits also connect directly to the data link connector (DLC).

  1. Supply voltage to the devices are in the normal operating range.
  2. The vehicle power mode requires serial data communications.

The device setting the DTC has attempted to establish communications on the serial data circuits more than 3 times in 5 seconds.

  1. The device suspends all message transmission.
  2. The device uses default values for all parameters received on the serial data circuits.
  3. The device inhibits the setting of all other communication DTCs.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the device ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Diagnosis is accomplished using the symptom. Refer to Scan Tool Does Not Communicate with Low Speed GMLAN Device .

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptor

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U0100-U02FFU0100-U02FF
Module IgnitionU0100-U02FFU0100-U02FF
Accessory Wakeup Serial DataU1814U0100-U02FF
Serial Data Communication EnableU2099U0100-U02FF
Chassis High Speed GMLAN Serial Data (+)4U0100-U02FF4
Chassis High Speed GMLAN Serial Data (-)4U0100-U02FF4
Mid Speed GMLAN Serial Data (+)3U0100-U02FF3
Mid Speed GMLAN Serial Data (-)3U0100-U02FF3
High Speed GMLAN Serial Data (+)2U0100-U02FF2
High Speed GMLAN Serial Data (-)2U0100-U02FF2
Low Speed GMLAN Serial Data1U0100-U02FF1
Module GroundU0100-U02FF
1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with high speed GMLAN device 3. Scan tool does not communicate with mid speed GMLAN device 4. Scan tool does not communicate with chassis high speed GMLAN device

The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the data link connector (DLC), the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the control module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.

The system voltage is between 9-16 V.

A supervised periodic message that includes the transmitter module availability has not been received.

  1. Specific subsystems will not function.
  2. DTC U0100 in the TCM will cause the transmission to go into default gears.
  3. Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
  4. DTC U0100 and/or U0101 in the hybrid powetrain control module will cause the malfunction indicator lamp (MIL) to illuminate and the engine to operate in conventional mode.
  1. The ECM/TCM module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
  2. The hybrid powertrain control module DTC clears when the malfunction is no longer present. The hybrid operation returns to normal after an ignition cycle and ignition off for greater than 5 seconds.
  3. A current DTC clears when the malfunction is no longer present.
  4. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine if the control module uses high or low speed GMLAN serial data communications.
  6. Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.
  7. Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against, and any inline harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition..
  8. This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Determine the control module that is not communicating. Refer to «Control Module U Code List»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__control-module-u-code-list) .
  2. Verify that DTC U0073, U2100, U0074, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. Engine running for 10 seconds.
  4. Ignition ON, engine OFF, verify that DTC U0100-U02FF is not set with symptom byte 00. If the DTC U0100-U02FF is set with symptom byte 00, refer to Circuit/System Testing.
  5. Verify that DTC U0100-U02FF is not set with symptom byte 71 or 72. If the DTC U0100-U02FF is set with symptom byte 71 or 72 along with other DTCs set, diagnose all other codes first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If the DTC U0100-U02FF is set with symptom byte 71 or 72 and without other DTCs set, reprogram the control module. If the DTC resets, replace the control module.
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.

Note. Use the schematic to identify the following: Control modules the vehicle is equipped with Control module locations on the low and high speed GMLAN serial data circuits The control module's B+, ignition, ground, communication enable and serial data circuit terminals

  1. Using the High Voltage Module Chart below, verify that the non-communicating control module is not a high voltage module. If the control module is a high voltage module, perform the High Voltage Disabling procedure before proceeding with this diagnostic. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. If high voltage disabling is required, reconnect the 12 V battery after performing the high voltage disabling procedure.
  3. Ignition OFF, disconnect the harness connector at of the control module that is not communicating.
  4. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  8. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters away from vehicle. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the serial data circuit terminals and the appropriate X84 data link connector (DLC) terminal listed below: Low speed GMLAN serial data terminal 1 High speed GMLAN serial data terminal 6 or 14 Mid speed GMLAN serial data terminal 3 or 11 Chassis high speed GMLAN serial data terminal 12 or 13 If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a module setting the DTC or a serial data splice pack.
  9. If all circuits test normal, replace the control module that is not communicating.
ModuleVoltage SystemData Link Type
K16 Battery Energy Control Module300 V 12 VHigh Speed GMLAN Powertrain High Speed GMLAN
K114 Hybrid Powertrain Control Module or K59 Starter/Generator Control Module300 V 12 VHigh Speed GMLAN Powertrain High Speed GMLAN

High Voltage Module Chart

Perform the Diagnostic Repair Verification after completing the repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U0100-U02FFU0100-U02FF
Module IgnitionU0100-U02FFU0100-U02FF
Accessory Wake Up Serial DataU1814U0100-U02FF
Serial Data Communication EnableU2099U0100-U02FF
Chassis High Speed GMLAN Serial Data (+)4U0100-U02FF4
Chassis High Speed GMLAN Serial Data (-)4U0100-U02FF4
Mid Speed GMLAN Serial Data (+)3U0100-U02FF3
Mid Speed GMLAN Serial Data (-)3U0100-U02FF3
High Speed GMLAN Serial Data (+)2U0100-U02FF2
High Speed GMLAN Serial Data (-)2U0100-U02FF2
Low Speed GMLAN Serial Data1U0100-U02FF1
Module GroundU0100-U02FF
1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with high speed GMLAN device 3. Scan tool does not communicate with mid speed GMLAN device 4. Scan tool does not communicate with chassis high speed GMLAN device

The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the data link connector (DLC), the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the control module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.

The system voltage is between 9-16 V.

A supervised periodic message that includes the transmitter module availability has not been received.

  1. Specific subsystems will not function.
  2. DTC U0100 in the TCM will cause the transmission to go into default gears.
  3. Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
  1. The ECM/TCM module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
  2. A current DTC clears when the malfunction is no longer present.
  3. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine if the control module uses high or low speed GMLAN serial data communications.
  6. Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.
  7. Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against, and any inline harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition..
  8. This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Determine the control module that is not communicating. Refer to «Control Module U Code List»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__control-module-u-code-list) .
  2. Verify that DTC U0073, U2100, U0074, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. Engine running for 10 seconds.
  4. Ignition ON, engine OFF, verify that DTC U0100-U02FF is not set with symptom byte 00. If the DTC U0100-U02FF is set with symptom byte 00, refer to «Circuit/System Testing»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  5. Verify that DTC U0100-U02FF is not set with symptom byte 71 or 72. If the DTC U0100-U02FF is set with symptom byte 71 or 72 along with other DTCs set, diagnose all other codes first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If the DTC U0100-U02FF is set with symptom byte 71 or 72 and without other DTCs set, reprogram the control module. If the DTC resets, replace the control module.

Note. Use the schematic to identify the following: Control modules the vehicle is equipped with Control module locations on the low and high speed GMLAN serial data circuits The control modules B+, ignition, ground, communication enable and serial data circuit terminals

  1. Ignition OFF, disconnect the harness connector at of the control module that is not communicating.
  2. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module (BCM), for an open/high resistance or short to ground. If the circuits test normal, replace the K9 BCM.
  6. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters away from vehicle. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the serial data circuit terminals and the appropriate X84 data link connector (DLC) terminal listed below: Low speed GMLAN serial data terminal 1 High speed GMLAN serial data terminal 6 or 14 Mid speed GMLAN serial data terminal 3 or 11 Chassis high speed GMLAN serial data terminal 12 or 13 If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a module setting the DTC or a serial data splice pack.
  7. If all circuits test normal, replace the control module that is not communicating.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Some control modules must be configured with specific software, serial numbers, vehicle options, or other information. If a control module was not properly configured after installation that module may set the appropriate U Code. No external circuit diagnosis is involved.

Battery voltage is between 9-16 V and data link communications operate normally.

The control module is not configured properly.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify the appropriate DTC is not set.

  1. If the DTC is set, program the control module specified by the DTC descriptor. If the DTC resets, replace the control module specified by the DTC descriptor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Some control modules are constantly receiving information from other control modules through serial data communication network. The invalid data code will be set when a receiving control module detects a discrepancy in information it receives from another control module causing its integrity to be questioned. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.

Battery voltage is between 9-16 V and data link communications operate normally.

The control module is not configured properly.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Engine running for 10 seconds.
  2. Ignition ON, engine OFF, verify the DTC U0400-U05FF is not set. If the DTC U0400-U05FF is set along with other DTCs set, diagnose all other codes first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If the DTC U0400-U05FF is set without other DTCs set, program the control module specified by the DTC descriptor. If the DTC resets, replace the appropriate control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The serial data is transmitted over a Local Interconnect Network (LIN) single wire network circuit bus between a master control module and other control modules within a particular subsystem. If serial data communication is lost between any of the control modules on the LIN bus network, a no communication code against the non-communicating control module will be set. A master control module is the one that reports the non communication code. Note: a loss of serial data communications DTC does not represent a failure of the master control module that set it.

  1. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  2. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  3. Communication will be available between the master control module and the scan tool if there is a loss of communications with any of the other control modules on the LIN bus network.
  4. An open in the LIN bus serial data circuit between the splice pack and a module will only affect that specific module. This type of failure will set a loss of communication DTC for each control module affected and the other control modules will still communicate.
  5. Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against, and any inline harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition..

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Note. Use the schematic to identify the following: LIN devices the vehicle are equipped with The LIN device's B+, ignition, ground, and serial data circuit terminals Use the Control Module U-Code list to determine which control module is not communicating with the master control module. Refer to Control Module U Code List . A loss of serial data communications DTC does not represent a failure of the master control module that set it.

  1. Ignition OFF, disconnect the harness connector at a LIN device that is not communicating.
  2. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the LIN device for a short to ground. If the circuits test normal, replace the LIN device.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the LIN device for a short to ground. If the circuits test normal, replace the LIN device.
  5. Ignition ON, test for 2-12 V between the LIN serial data circuit and ground. If greater than the specified range, test the LIN serial data circuit for a short to voltage. If the circuit tests normal, replace the master control module. If less than the specified range, test the LIN serial data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the master control module.
  6. If all circuits test normal, replace the LIN device.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The high speed GMLAN serial data circuits are serial data buses used to communicate information between the control modules. The high speed GMLAN serial data circuits connect directly to the data link connector (DLC) for programming purposes.

This diagnostic is used to check the high speed GMLAN communication bus status.

  1. The ignition is ON.
  2. The system voltage is greater than 8.8 V.

The control module setting the DTC has attempted to establish communications on the serial data circuits for more than 1.4 seconds without success.

The DTC U180B is a type B DTC.

The DTC U180B is a type B DTC.

Diagnosis is accomplished using the symptom. Refer to Scan Tool Does Not Communicate with High Speed GMLAN Device .

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The powertrain high speed GMLAN serial data circuits are serial data buses used to communicate information between the control modules.

This diagnostic is used to check the powertrain high speed GMLAN communication bus status.

  1. The ignition is ON.
  2. The system voltage is greater than 8.8 V.

The control module setting the DTC has attempted to establish communications on the serial data circuits for more than 1.4 seconds without success.

The DTC U1811 is a type B DTC.

The DTC U1811 is a type B DTC.

Verify that DTC U0074 is not set.

  1. If the DTC is set, refer to «DTC U0074 (Mid Speed or Chassis Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0074 (Powertrain Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Powertrain Serial Data Communication EnableU1814, 1U0100-U02FF
1. Vehicle will not start.

The body control module (BCM) activates the serial data communication enable circuit when the ignition key is in ACC, ON or START. The serial data communication enable circuit wakes up the engine control module (ECM) for serial data bus communication.

  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.

The BCM senses a short to ground on the serial data communication enable circuit.

  1. The output command is turned off while the malfunction is present.
  2. The modules use a default value for the missing parameters until the next ignition cycle.
  3. The module(s) is never signaled, therefore the specific subsystem(s) will not function.
  4. The vehicle will not start while the circuit is shorted to ground.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Use the DMM MIN/MAX function to capture/locate intermittent conditions.
  2. Short to ground will also set multiple history no communication codes for GMLAN high speed modules.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Note. Use the schematic to determine which control modules are on the BCM communications enable circuit 22, X4.

  1. Ignition OFF, disconnect the harness connector at the most easily accessible control module on the K9 BCM communications enable circuit.
  2. Ignition ON, retest for current DTCs. DTC U1814 should remain current. If the DTC becomes history, replace the control module that was just disconnected.
  3. With the prior control modules disconnected, repeat steps 1 and 2 for each control module on the circuit except the K9 BCM.
  4. Ignition OFF, disconnect the X4 harness connector at the K9 BCM.
  5. Test for infinite resistance between the serial data communication enable circuit terminal 22 X4 and ground. If less than infinite resistance, repair the communications enable circuit for a short to ground.
  6. If all circuits tests normal, replace the K9 BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1817U1817
IgnitionU1817U1817
Accessory Wake Up Serial DataU1814, U1817*U1817*
Powertrain High Speed GMLAN Serial Data (+)U0074*U0074, U1817*U0074*
Powertrain High Speed GMLAN Serial Data (-)U0074*U0074, U1817*U0074*
GroundU1817*
* Other DTCs may set with this fault.

Control modules connected to the powertrain high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The motor control module and the hybrid powertrain control module are all internal to the starter/generator control module. All circuits to the hybrid powertrain control module are also internal to the starter/generator control module.

Communication diagnostics for the serial data, including control module power and ground as well as the wakeup circuits for the motor control module and the hybrid powertrain control module are all diagnosed from external sources only to the starter/generator control module connector because any circuit fault condition within the starter/generator control module will cause a complete replacement.

  1. The system voltage is more than 10 V.
  2. The vehicle power mode master requires serial data communication to occur from this specific control module.

A supervised periodic message that includes the transmitter module availability has not been received.

DTC U1817 is a type A DTC.

DTC U1817 is a type A DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0074, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. Verify that DTCs U1818, U182A, U1844, and U1847 are not set. If all the DTCs are set, refer to «DTC U0074 (Mid Speed or Chassis Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0074 (Powertrain Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  4. Test for less than 10 ohms between the K59 starter/generator control module case and ground. If greater than the specified range, check the ground connection at the housing.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K59 starter/generator control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K59 starter/generator control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  8. Ignition OFF, disconnect the harness connector at the control module setting the DTC.
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each powertrain high speed GMLAN serial data circuit between the K59 starter/generator control module and the control module setting the DTC. If greater than the specified range, test the serial data circuit for an open/high resistance between the K59 starter/generator control module and the control module setting the DTC.
  10. If all circuits test normal, replace the K59 starter/generator control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1818U1818
IgnitionU1818U1818
Accessory Wake Up Serial DataU1814, U1818*U1818
Powertrain High Speed GMLAN Serial Data (+)U0074*U0074, U1818*U0074*
Powertrain High Speed GMLAN Serial Data (-)U0074*U0074, U1818*U0074*
GroundU1818
* Other DTCs may set with this fault.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

  1. The system voltage is greater than 9.5 V.
  2. The vehicle power mode master requires serial data communication to occur from this specific control module.

A supervised periodic message that includes the transmitter module availability has not been received for more than 500 ms.

DTC U1818 is a type B DTC.

DTC U1818 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0100 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0074, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. Verify that DTCs U1817, U182A, U1844, and U1847 are not set. If all the DTCs are set, refer to «DTC U0074 (Mid Speed or Chassis Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0074 (Powertrain Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  1. Ignition OFF, disconnect harness connector at the K20 engine control module (ECM).
  2. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  6. Ignition OFF, disconnect the low voltage harness connector at the control module setting the DTC.
  7. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each serial data circuit between the K20 ECM and the control module setting the DTC. If greater than the specified range, test the serial data circuit for an open/high resistance between the K20 ECM and the control module setting the DTC.
  8. If the circuits test normal, replace the K20 ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U182A*U182A
IgnitionU182A*U182A
Accessory Wake Up Serial DataU1814, U182A*U182A*
Powertrain High Speed GMLAN Serial Data (+)U0074*U0074, U182A*U0074*
Powertrain High Speed GMLAN Serial Data (-)U0074*U0074, U182A*U0074*
GroundU182A*
* Multiple DTCs may be set and multiple symptoms including a no start condition may occur.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The system voltage is greater than 9.5 V.

A supervised periodic message that includes the transmitter module availability has not been received for more than 3 seconds.

DTC U182A is a type B DTC.

DTC U182A is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0074, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. Verify that DTCs U1817, U1818, U1844, and U1847 are not set. If the DTC is set, refer to «DTC U0074 (Mid Speed or Chassis Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0074 (Powertrain Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the low voltage harness connector at the K16 battery energy control module (BECM).
  4. Test for less than 10 ohms between the K16 BECM case and ground. If greater than the specified range, check the ground connection at the housing.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance between K16 BECM and the K59 starter/generator control module. If the circuit tests normal, replace the K59 starter/generator control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance between K16 BECM and the K59 starter/generator control module. If the circuit tests normal, replace the K59 starter/generator control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the accessory wake up serial data circuit for an open/high resistance or short to ground between K16 BECM and the K59 starter/generator control module. If the circuit tests normal, replace the K59 starter/generator control module.
  8. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each powertrain high speed GMLAN serial data circuit between the K16 BECM and the K59 starter/generator control module. If greater than the specified range, test the serial data circuit for an open/high resistance between the K16 BECM and the K59 starter/generator control module.
  10. If all circuits test normal, replace the K16 BECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The motor control module and the hybrid powertrain control module are all internal to the starter/generator control module. The hybrid powertrain control module sends out diagnostic trouble code information to other control modules regarding the motor control module. All circuits to the hybrid powertrain control module and motor control module are also internal to the starter/generator control module and replaced as a single component.

Communication diagnostics for the serial data, including control module power and ground as well as the wakeup circuits for motor control module and the hybrid powertrain control module are all diagnosed from external sources only to the starter/generator control module connector because any circuit fault condition within the starter/generator control module will cause a complete replacement.

  1. The system voltage is greater than 9.5 V.
  2. The vehicle power mode master requires serial data communication to occur from this specific control module.

A supervised periodic message that includes the transmitter module availability has not been received for more than 500 ms.

The DTC U1831 is a type B DTC.

The DTC U1831 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.
  4. If DTC U1831 is only set current in the hybrid powertrain control module, the starter/generator control module must be replaced due to all circuits between the hybrid powertrain control module and motor control module being internal to the starter/generator control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Verify that DTC U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U1831 is not set current only in the K114 hybrid powertrain control module. If the DTC is set current in the K114 hybrid powertrain control module only, replace the K59 starter/generator control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1844*U1844
IgnitionU1844*U1844*
Accessory Wake Up Serial DataU1814, U1844*U1844*
Powertrain High Speed GMLAN Serial Data (+)U0074*U0074, U1844*U0074*
Powertrain High Speed GMLAN Serial Data (-)U0074*U0074, U1844*U0074*
GroundU1844*
* Other modules/DTCs may set with this fault and multiple symptoms including a no start condition may occur.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

This diagnostic is used to check the loss of communication with hybrid powertrain control module on powertrain high speed GMLAN bus. The battery energy control module supervises a periodic serial data message to check the communication status of the hybrid powertrain control module. If this message is not received within 3 seconds, then this DTC is set.

  1. The system voltage is greater than 8.8 V.
  2. The DTC U1811 is not set.

A supervised periodic message that includes the transmitter module availability has not been received within 3 seconds.

The DTC U1844 is a type B DTC.

The DTC U1844 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0073, U0074, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. 3. Verify that DTCs U1817, U1818, U182A, and U1847 are not set. If all the DTCs are set, refer to «DTC U0074 (Mid Speed or Chassis Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0074 (Powertrain Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  4. Test for less than 10 ohms between the K59 starter/generator control module case and ground. If greater than the specified range, check the ground connection at the housing.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K59 starter/generator control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K59 starter/generator control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  8. Ignition OFF, disconnect the low voltage harness connector at the K16 battery energy control module (BECM).
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each powertrain high speed GMLAN serial data circuit between the K59 starter/generator control module and the K16 BECM. If greater than the specified range, test the serial data circuit for an open/high resistance between the K59 starter/generator control module and the K16 BECM.
  10. If all circuits test normal, replace the K59 starter/generator control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The motor control module and the hybrid powertrain control module are all internal to the starter/generator control module. The hybrid powertrain control module sends out diagnostic trouble code information to other control modules regarding the motor control module. All circuits to the hybrid powertrain control module and motor control module are also internal to the starter/generator control module and replaced as a single component.

Communication diagnostics for the serial data, including control module power and ground as well as the wakeup circuits for motor control module and the hybrid powertrain control module are all diagnosed from external sources only to the starter/generator control module connector because any circuit fault condition within the starter/generator control module will cause a complete replacement.

  1. The system voltage is greater than 9.5 V.
  2. The vehicle power mode master requires serial data communication to occur from this specific control module.

A supervised periodic message that includes the transmitter module availability has not been received for more than 500 ms.

The DTC U1845 is a type B DTC.

The DTC U1845 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.
  4. If DTC U1845 is only set current in the hybrid powertrain control module, the starter/generator control module must be replaced due to all circuits between the hybrid powertrain control module and motor control module being internal to the starter/generator control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Verify that DTC U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U1845 is not set current only in the K114 hybrid powertrain control module. If the DTC is set current in the K114 hybrid powertrain control module only, replace the K59 starter/generator control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1847*U1847
IgnitionU1847*U1847*
Accessory Wake Up Serial DataU1814, U1847*U1847*
Powertrain High Speed GMLAN Serial Data (+)U0074*U0074, U1847*U0074*
Powertrain High Speed GMLAN Serial Data (-)U0074*U0074, U1847*U0074*
GroundU1847*
* Other modules/DTCs may set with this fault and multiple symptoms including a no start condition may occur.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

  1. The ignition is ON.
  2. The system voltage is greater than 9.5 V.

A supervised periodic message that includes the transmitter module availability has not been received for more than 500 ms.

The DTC U1847 is a type B DTC.

The DTC U1847 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0073, U0074, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  2. Verify that DTCs U1817, U1818, U182A, and U1844 are not set. If all the DTCs are set, refer to «DTC U0074 (Mid Speed or Chassis Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0074 (Powertrain Expansion Bus)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the low voltage harness connector at the K16 battery energy control module.
  4. Test for less than 10 ohms between the K16 battery energy control module case and ground. If greater than the specified range, check the ground connection at the housing.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K16 battery energy control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K16 battery energy control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the accessory wake up serial data circuit for an open/high resistance or short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  8. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each powertrain high speed GMLAN serial data circuit between the K16 battery energy control module and the K59 starter/generator control module. If greater than the specified range, test the serial data circuit for an open/high resistance between the K16 battery energy control module and the K59 starter/generator control module.
  10. If all circuits test normal, replace the K16 battery energy control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1875*U1875
IgnitionU1875*U1875*
Accessory Wake Up Serial DataU1814, U1875*U1875*
High Speed GMLAN Serial Data (+)U0073*U0073, U1875*U0073*
High Speed GMLAN Serial Data (-)U0073*U0073, U1875*U0073*
GroundU1875*
* Other modules/DTCs may set with this fault and multiple symptoms including a no start condition may occur.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

  1. The ignition is ON.
  2. The system voltage is greater than 9.5 V.

A supervised periodic message that includes the transmitter module availability has not been received within 3 seconds.

The DTC U1875 is a type B DTC.

The DTC U1875 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Verify that DTC U0073, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set.

  1. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the low voltage harness connector at the K16 battery energy control module.
  4. Test for less than 10 ohms between the K16 battery energy control module case and ground. If greater than the specified range, check the ground connection at the housing.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K16 battery energy control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K16 battery energy control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the accessory wake up serial data circuit for an open/high resistance or short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  8. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each serial data circuit between the K16 battery energy control module and the K59 starter/generator control module. If greater than the specified range, test the serial data circuit for an open/high resistance between the K16 battery energy control module and the K59 starter/generator control module.
  10. If all circuits test normal, replace the K16 battery energy control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1876U1876
IgnitionU1876U1876
Accessory Wake Up Serial DataU1814, U1876*U1876
High Speed GMLAN Serial Data (+)U0073*U0073, U1876*U0073*
High Speed GMLAN Serial Data (-)U0073*U0073, U1876*U0073*
GroundU1876
* Other DTCs may set with this fault.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

  1. The system voltage is greater than 9.5 V.
  2. The vehicle power mode master requires serial data communication to occur from this specific control module.

A supervised periodic message that includes the transmitter module availability has not been received for more than 500 ms.

DTC U1876 is a type B DTC.

DTC U1876 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0100 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0073, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  1. Ignition OFF, disconnect harness connector at the K20 engine control module (ECM).
  2. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  6. Ignition OFF, disconnect the harness connector at the K59 starter/generator control module.
  7. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each serial data circuit between the K20 ECM and the K59 starter/generator control module. If greater than the specified range, test the serial data circuit for an open/high resistance between the K20 ECM and the K59 starter/generator control module.
  8. If the circuits test normal, replace the K20 ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1885*U1885
IgnitionU1885*U1885*
Accessory Wake Up Serial DataU1814, U1885*U1885*
High Speed GMLAN Serial Data (+)U0073*U0073, U1885*U0073*
High Speed GMLAN Serial Data (-)U0073*U0073, U1885*U0073*
GroundU1885*
* Other modules/DTCs may set with this fault and multiple symptoms including a no start condition may occur.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

This diagnostic is used to check the loss of communication with hybrid powertrain control module on high speed GMLAN bus. The battery energy control module supervises a periodic serial data message to check the communication status of the hybrid powertrain control module. If this message is not received within 3 seconds, then this DTC is set.

  1. The system voltage is greater than 8.8 V.
  2. The DTC U180B is not set.

A supervised periodic message that includes the transmitter module availability has not been received within 3 seconds.

The DTC U1885 is a type B DTC.

The DTC U1885 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0073, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  2. Reconnect the 12 V battery.
  3. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  4. Test for less than 10 ohms between the K59 starter/generator control module case and ground. If greater than the specified range, check the ground connection at the housing.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K59 starter/generator control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K59 starter/generator control module for a short to ground. If the circuits test normal, replace the K59 starter/generator control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  8. Ignition OFF, disconnect the low voltage harness connector at the K16 battery energy control module.
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each serial data circuit between the K59 starter/generator control module and the K16 battery energy control module. If greater than the specified range, test the serial data circuit for an open/high resistance between the K59 starter/generator control module and the K16 battery energy control module.
  10. If all circuits test normal, replace the K59 starter/generator control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1886U1886
IgnitionU1886U1886
Accessory Wake Up Serial DataU1814, U1886*U1886
High Speed GMLAN Serial Data (+)U0073*U1886*U0073*
High Speed GMLAN Serial Data (-)U0073*U1886*U0073*
GroundU1886
* Other DTCs may set with this fault.

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

  1. The system voltage is greater than 8.8 V.
  2. The DTC U180B is not set.

A supervised periodic message that includes the transmitter module availability has not been received.

DTC U1886 is a type B DTC.

DTC U1886 is a type B DTC.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine what GMLAN serial data communications the non communicating control module uses.
  6. The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Verify that DTC U0100 or U0293 is not set. If the DTC is set, refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Verify that DTC U0073, U1814, B1428, B1370, B1380, B1440, B1441, B1325, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.
WARNINGThe eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
  1. Ignition OFF, disconnect harness connector at the K20 engine control module (ECM).
  2. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  6. Ignition OFF, disconnect the low voltage harness connector at the K59 starter/generator control module.
  7. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each serial data circuit between the K20 ECM and the K59 starter/generator control module. If greater than the specified range, test the serial data circuit for an open/high resistance between the K20 ECM and the K59 starter/generator control module.
  8. Perform the High Voltage Disabling procedure. Refer to «High Voltage Disabling»(/buick/regal/v-2009-2013/remont/body-electrical/#hybridev-energy-storage-system__high-voltage-disabling) .
  9. Reconnect the 12 V battery.
  10. Ignition OFF, disconnect the low voltage harness connector at the K16 battery energy control module (BECM).
  11. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each serial data circuit between the K59 starter/generator control module and the K16 BECM. If greater than the specified range, test the serial data circuit for an open/high resistance between the K59 starter/generator control module and the K16 BECM.
  12. If the circuits test normal, replace the K20 ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Control modules on the high speed GMLAN serial data bus and the chassis high speed GMLAN serial data bus must be programmed with software that specifically identifies the correct type and quantity of modules on the bus based on RPO configuration. If a control module was not properly configured after installation, the appropriate U Code may be set for that module. No external circuit diagnosis is involved.

  1. Voltage supplied to the module is in the normal operating voltage range.
  2. The vehicle power mode requires serial data communication to occur.
  1. The control module is not configured properly.
  2. Control unit recognises a programming error.
  3. CAN-Bus configuration is invalid
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Verify the appropriate DTC is not set. If the DTC is set along with other codes, diagnose all other codes first. If no other codes are set, program the control module that set the DTC.
  2. With a scan tool, clear the DTCs.
  3. Ignition OFF, remove the scan tool, open and close the drivers door.
  4. Wait 60 seconds, then verify the DTC is not set. If the DTC is set, replace the appropriate control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+11
Serial Data1U1901 00U1901 00U1901 00
Ground11
1. S56 Radio Control Multifunction Switch Malfunction

The radio interfaces only with the Info Display Module and the Info Display Module communicates with the radio/HVAC control through a LIN interface. The Info Display Module is responsible for passing information between the radio and the radio/HVAC control.

  1. The system voltage is between 9-16 V.
  2. The vehicle power mode master requires serial data communication to occur.
  1. A supervised periodic message that includes the transmitter module availability has not been received.
  2. Radio detects an invalid signal from S56 radio control multifunction switch.

Radio menu navigation and control will not function with the multifunction controller.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Radio/Navigation System Schematics»(/buick/regal/v-2009-2013/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system)

Connector End View Reference

Description and Operation

  1. «Data Link Communications Description and Operation»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-communications-description-and-operation)
  2. «Radio/Audio System Description and Operation»(/buick/regal/v-2009-2013/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system__radioaudio-system-description-and-operation)

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the S56 radio control multifunction switch.
  2. Test for less than 10 ohms between ground circuit and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between B+ circuit and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the S56 radio control multifunction switch.
  4. Test for 2-12 V between the serial data circuit and ground. If greater than the specified range, test the serial data circuit for a short to voltage. If the circuit tests normal, replace the A22 radio controls. If less than the specified range, test the serial data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the A22 radio controls.
  5. If all circuits test normal, replace the S56 radio control multifunction switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Audio Multifunction Control Replacement»(/buick/regal/v-2009-2013/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system)
  3. «Radio Control Module Replacement»(/buick/regal/v-2009-2013/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system)
  4. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Serial Data Communication EnableU2099, U0100-U02FF 1U0100-U02FFU0100-U02FF 2
1 Vehicle will not start. 2 History only. If cleared the DTC will return after several ignition cycles.

The body control module (BCM) activates the serial data communication enable circuit, when the ignition key is in ACC, ON or START. The serial data communication enable circuit wakes up the control modules for serial data buss communication.

  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.

The BCM senses a short to ground on the serial data communication enable circuit.

  1. The output command is turned off while the malfunction is present.
  2. The control modules use a default value for the missing parameters until the next ignition cycle.
  3. The control module(s) is never signaled, therefore the specific subsystem(s) will not function.
  4. The vehicle will not start while the circuit is shorted to ground.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Use the DMM MIN/MAX function to capture/locate intermittent conditions.
  2. Short to ground will also set multiple history no communication codes for GMLAN high speed modules.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Note. Use the schematic to determine which control modules are on the BCM communications enable circuit 23, X4.

  1. Ignition OFF, disconnect the harness connector at the most easily accessible control module on the K9 BCM communication enable circuit.
  2. Ignition ON, retest for current DTCs. DTC U2099 should remain current. If the DTC becomes history, replace the control module that was just disconnected.
  3. With the prior control modules disconnected, repeat steps 1 and 2 for each control module on the circuit except the K9 BCM.
  4. Ignition OFF, disconnect the X4 harness connector at the K9 BCM.
  5. Test for infinite resistance between the serial data communication enable circuit terminal 23 X4 and ground. If less than infinite resistance, repair the communication enable circuit for a short to ground.
  6. If all circuits tests normal, replace the K9 BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Some control modules must be programmed with software that specifically identifies the correct type and quantity of modules on the serial data bus based on RPO configuration. If a control module was not properly configured after installation, the appropriate U Code may be set for that module. No external circuit diagnosis is involved.

  1. Voltage supplied to the module is in the normal operating voltage range.
  2. The vehicle power mode requires serial data communication to occur.
  1. The control module is not configured properly.
  2. Control unit recognises a programming error.
  3. CAN-Bus configuration is invalid
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Verify the appropriate DTC is not set. If the DTC is set along with other codes, diagnose all other codes first. If no other codes are set, program the control module specified by the DTC descriptor.
  2. With a scan tool, clear the DTCs.
  3. Ignition OFF, remove the scan tool, open and close the drivers door.
  4. Wait 60 seconds, then verify the DTC is not set. If the DTC is set, replace the appropriate control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Modules connected to the GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have programmed information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are also supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module.

DTC U2103 will set when fewer modules are detected on the buss before the modules can learn the other module IDs. If the communication buss is opened, or if the module power supply is lost when the vehicle is in the OFF power mode, and then placed in the RUN power mode, U2103 will set in specific modules.

  1. Voltage supplied to the modules is in the normal operating voltage range.
  2. The vehicle power mode requires serial data communication to occur.
  3. The DTC U2100 does not have a current status.

A supervised periodic message that includes the transmitter module availability has not been received.

The module uses a default value for the missing parameter.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
  1. Diagnosis of this DTC is accomplished via the symptom or an additional DTC. Refer to «Symptoms - Data Communications»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__symptoms-data-communications) , or «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) procedure in order to isolate an intermittent condition.
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using the diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U2105-U2199U2105-U2199
Module IgnitionU2105-U2199U2105-U2199
Accessory Wakeup Serial DataU1814U2105-U2199
Serial Data Communication EnableU2099U2105-U2199
High Speed GMLAN Serial Data (+)2U2105-U21992
High Speed GMLAN Serial Data (-)2U2105-U21992
Low Speed GMLAN Serial Data1U2105-U21991
Module GroundU2105-U2199
1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with high speed GMLAN device

Control modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The body control module (BCM) activates the high speed GMLAN serial data wake up and the accessory wake up serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The high speed GMLAN serial data wake up circuit wakes up the electronic brake control module (EBCM) for bus communication and the accessory wake up serial data circuit wakes up the engine control module (ECM) and transmission control module (TCM).

  1. The system voltage is between 9-16 V.
  2. The vehicle power mode requires serial data communication to occur.

A supervised periodic message that includes the transmitter module availability has not been received.

The control module uses a default value for the missing parameters.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. If there are multiple non-communicating modules choose the one closest to the data link connector (DLC).
  2. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  3. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  4. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  5. Use «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) to determine if the control module uses high or low speed GMLAN serial data communications
  6. Some control modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no control module output voltage circuit is shorted to ground before replacing the control module.
  7. Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against, and any inline harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition.
  8. This diagnostic can be used for any control module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that control module.
  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Determine the control module that is not communicating. Refer to «Control Module U Code List»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__control-module-u-code-list) .
  2. Verify that DTC U0073, U2100, U0074, U0078, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .

Note. Terminal and connector identifiers will be different depending on the individual control module being tested. Use Schematic Reference and Connector End View Reference to identify control module's connector, B+, ignition, ground, communication enable and serial data circuit terminals.

  1. Ignition OFF, disconnect the harness connector at the control module that is not communicating.
  2. Ignition OFF, test for less than 10 ohms between each ground circuit terminal and ground. If greater than specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the control circuits of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the control circuits of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  6. Ignition OFF, disconnect the harness connectors at the control module setting the DTC.
  7. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters away from vehicle. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in each GMLAN serial data circuit between the non-communicating control module and the control module setting the DTC. If greater than specified range, test the GMLAN serial data circuit for open/high resistance.
  8. If all circuits test normal, replace the control module that is not communicating.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup

Symptoms - Data Communications

IMPORTANTThe following steps must be completed before using the symptom tables.
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) before using the symptom tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data links.
  2. Review the system operation in order to familiarize yourself with the system functions. Refer to «Data Link Communications Description and Operation»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-communications-description-and-operation) .

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__checking-aftermarket-accessories) .
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. «Scan Tool Does Not Power Up»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  3. «Scan Tool Does Not Communicate with Mid Speed GMLAN Device»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  4. «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  5. «Scan Tool Does Not Communicate with Chassis High Speed GMLAN Device»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
DLC B+11
DLC Ground1
1. Scan Tool Does Not Power Up

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following

  1. Scan tool B+ voltage at terminal 16
  2. Scan tool ground at terminal 4
  3. Common ground at terminal 5
  1. The scan tool will power up with the ignition OFF. Some modules however, will not communicate unless the ignition is ON and the power mode master module sends the appropriate power mode message.
  2. If the B+ circuit, ground circuits, and connections of the DLC are functioning properly, the malfunction must be due to the scan tool.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information.

  1. Test for less than 2.0 ohms between the ground circuits terminal 4 of the DLC and ground, and terminal 5 of the DLC and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 16 at the DLC and ground. If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance.
  3. If all circuits test normal, refer to the scan tool user guide.

Perform the Diagnostic Repair Verification after completing the repair.

  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Chassis High Speed GMLAN Serial Data (+)1U0100-U02FF*1
Chassis High Speed GMLAN Serial Data (-)1U0100-U02FF*1
Ground (DLC, terminal 5)1
* No communications with one or more chassis high speed GMLAN modules. An open in only one chassis high speed GMLAN serial data circuit may allow degraded communication between the modules. An open between the data link connector (DLC) and the first splice will only effect the communication with the scan tool. The vehicle modules will still communicate. 1. No communication with any chassis high speed GMLAN module

The GMLAN high speed chassis expansion bus functions the same as the GMLAN high speed bus, and the two buses operate in parallel. The expansion chassis bus was added to reduce message congestion on the primary high speed bus. Since the GMLAN high speed chassis bus and primary GMLAN high speed bus operate in the same manner, the diagnostics for each are the same.

The serial data is transmitted on two twisted wires that allow speeds up to 500 Kb/s. The twisted pair is terminated with two 120 ohms resistors, one is internal to the engine control module (ECM) and the other can be a separate resistor in a connector assembly or in another control module. The resistors are used as the load for the High Speed GMLAN buss during normal vehicle operation. The high speed GMLAN is a differential bus. The high speed GMLAN serial data bus (+) and high speed GMLAN serial data (-) are driven to opposite extremes from a rest or idle level of approximately 2.5 V. Driving the lines to their extremes, adds one volt to the high speed GMLAN serial data bus (+) circuit and subtracts one volt from the high speed GMLAN serial data bus (-) circuit. If serial data is lost, control modules will set a no communication code against the non-communicating control module. Note that a loss of serial data DTC does not represent a failure of the module that set it.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of-communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more modules was interrupted during diagnosis A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. Do not replace a control module reporting a U code. The U code identifies which control module needs to be diagnosed for a communication issue.
  3. Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
  4. An open in the DLC ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle.
  5. Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC).
  6. The engine may not start when there is a total malfunction of the chassis high speed GMLAN serial data bus.

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Note. Each control module may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following: Control modules the vehicle is equipped with Chassis high speed GMLAN serial data circuit terminating resistors Control module locations on the chassis high speed GMLAN serial data circuits Each control module chassis high speed GMLAN serial data circuit terminals

  1. Attempt to communicate with all control modules on the high speed GMLAN serial data circuit. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) . Communications should not be available with two or more control modules on the chassis high speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only. Refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Disconnect the scan tool from the X84 data link connector (DLC). The following tests will be done at the DLC connector.
  3. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuits listed below and ground: Terminal 12 Terminal 13 If greater than the specified range, test the serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to Voltage.
  5. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 100 ohms between the serial data circuits listed below and ground: Terminal 12 Terminal 13 If not the specified value, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to ground.
  6. Test for 50-70 ohms between the serial data circuits terminal 12 and terminal 13. If less than 35 ohms, test for a short between the serial data circuits. Refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance. Refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, test the serial data circuits between the DLC and the first connection to the serial data circuit for an open/high resistance.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at an easily accessible control module.
  2. Ignition ON, test for greater than 4.5 V between each serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was disconnected.
  3. Ignition OFF, disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at another control module, in the direction of the circuit shorted to voltage.
  4. Ignition ON, test for greater than 4.5 V between the serial data circuits at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to voltage on the serial data circuit between 2 control modules or splice packs, if equipped A short to voltage on the serial data circuit between a control module and a terminating resistor.

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at an easily accessible control module.
  2. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 1k ohms between each serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are less than 1k ohms. If all serial data circuits are greater than the specified range, replace the control module that was disconnected.
  3. Disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at another control module, in the direction of the circuit shorted to ground.
  4. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 1k ohms between the serial data circuits at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are less than 1k ohms. If greater than the specified range for all serial data circuits, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to ground on the serial data circuit between 2 control modules or splice packs, if equipped A short to ground on the serial data circuit between a control module and a terminating resistor.

Testing the Serial Data Circuits for a Short between the Circuits

  1. Ignition OFF, disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
  2. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are less than 110 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at another control module, in the direction of the circuits shorted together.
  5. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are less than 110 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: Serial data circuits shorted together between 2 control modules or splice packs, if equipped Serial data circuits shorted together between a control module and a terminating resistor A shorted terminating resistor

Testing the Serial Data Circuits for an Open/High Resistance

  1. Ignition OFF, disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
  2. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 130 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 130 ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at another control module, in the direction of the open circuit.
  5. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 130 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 130 ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: An open/high resistance on the serial data circuit between 2 control modules or splice packs, if equipped An open/high resistance on the serial data circuit between a control module and a terminating resistor An open/high resistance terminating resistor

Perform the Diagnostic Repair Verification after completing the repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
High Speed GMLAN Serial Data (+)1U0100-U02FF*1
High Speed GMLAN Serial Data (-)1U0100-U02FF*1
Ground (DLC, terminal 5)1
* No communications with one or more high speed GMLAN modules. An open in only one high speed GMLAN serial data circuit may allow degraded communication between the control modules. An open between the data link connector (DLC) and the first splice will only effect the communication with the scan tool. The vehicle control modules will still communicate. 1. No communication with any high speed GMLAN module

The serial data is transmitted on two twisted wires that allow speeds up to 500 Kb/s. The twisted pair is terminated with two 120 ohms resistors, one is internal to the engine control module (ECM) and the other can be a separate resistor in a connector assembly or in another control module. The resistors are used as the load for the High Speed GMLAN buss during normal vehicle operation. The high speed GMLAN is a differential bus. The high speed GMLAN serial data bus (+) and high speed GMLAN serial data (-) are driven to opposite extremes from a rest or idle level of approximately 2.5 V. Driving the lines to their extremes, adds 1 V to the high speed GMLAN serial data bus (+) circuit and subtracts 1 V from the high speed GMLAN serial data bus (-) circuit. If serial data is lost, control modules will set a no communication code against the non-communicating control module. Note that a loss of serial data DTC does not represent a failure of the control module that set it.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of-communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. Do not replace a control module reporting a U code. The U code identifies which control module needs to be diagnosed for a communication issue.
  3. Communication may be available between the BCM and the scan tool with the high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the high and low speed GMLAN systems.
  4. An open in the DLC ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle.
  5. Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC) and no low speed GMLAN communications with the scan tool.
  6. The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus. These conditions may be caused by the installation of an aftermarket navigation radio module (see bulletins). Some customers may comment of one or more of the following concerns: Vehicle will not crank Vehicle cranks but will not start Vehicle stability enhancement system warning lights and messages PRNDL gear indicator position errors

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Note. Each control module may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following: Control modules the vehicle is equipped with High speed GMLAN serial data circuit terminating resistors Control module locations on the high speed GMLAN serial data circuits Each control module's high speed GMLAN serial data circuit terminals

  1. Attempt to communicate with all control modules on the high speed GMLAN serial data circuit. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) . Communications should not be available with two or more control modules on the high speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only. Refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Disconnect the scan tool from the data link connector (DLC). The following tests will be done at the DLC connector.
  3. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuits listed below and ground: Terminal 6 Terminal 14 If greater than the specified range, test the serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to Voltage.
  5. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 100 ohms between the serial data circuits listed below and ground: Terminal 6 Terminal 14 If less than the specified range, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to ground.
  6. Test for 50-70 ohms between the serial data circuits terminal 6 and terminal 14. If less than 35 ohms, test for a short between the serial data circuits. Refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance. Refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, refer to Testing the DLC Serial Data Circuits for an Open.

Note. Some control modules with an internal terminating resistor have a loop in the harness that connects the internal terminating resistor to the serial data circuit. When wired this way, test these loop circuits for the appropriate failure mode short to voltage, short to ground, or open/high resistance prior to replacing the control module for each of the following tests.

Testing the DLC Serial Data Circuits for an Open

  1. Ignition OFF, disconnect the harness connectors at the body control module (BCM).
  2. Test for less than 2 ohms on each serial data circuit between the DLC and the BCM. If greater than the specified range, test the circuit for an open/high resistance.
  3. Test for less than 2 ohms on each serial data circuit between the BCM and the first splice or splice pack. If greater than the specified range, test the circuit for an open/high resistance.
  4. If the circuits test normal, replace the BCM.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at an easily accessible control module.
  2. Ignition ON, test for greater than 4.5 V between each serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was disconnected.
  3. Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at another control module, in the direction of the circuit shorted to voltage.
  4. Ignition ON, test for greater than 4.5 V between the serial data circuits at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to voltage on the serial data circuit between 2 control modules or splice packs, if equipped. A short to voltage on the serial data circuit between a control module and a terminating resistor.

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at an easily accessible control module.
  2. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 1k ohms between each serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are less than 1k ohms. If all serial data circuits are greater than the specified range, replace the control module that was disconnected.
  3. Disconnect the harness connectors with the high speed GMLAN serial data circuits at another control module, in the direction of the circuit shorted to ground.
  4. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 1k ohms between the serial data circuits at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are less than 1k ohms. If greater than the specified range for all serial data circuits, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to ground on the serial data circuit between 2 control modules or splice packs, if equipped. A short to ground on the serial data circuit between a control module and a terminating resistor. A short to ground on the serial data circuit between the DLC and the first control module or splice pack.

Testing the Serial Data Circuits for a Short between the Circuits

  1. Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
  2. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are less than 110 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Disconnect the harness connectors with the high speed GMLAN serial data circuits at another control module, in the direction of the circuits shorted together.
  5. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 110 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are less than 110 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: Serial data circuits shorted together between 2 control modules or splice packs, if equipped. Serial data circuits shorted together between a control module and a terminating resistor. Serial data circuits shorted together between the DLC and the first control module or splice pack. A shorted terminating resistor.

Testing the Serial Data Circuits for an Open/High Resistance

  1. Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at an easily accessible control module that is not communicating and has 2 or more pairs of serial data circuits or an internal terminating resistor.
  2. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 130 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 130 ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Disconnect the harness connectors with the high speed GMLAN serial data circuits at another control module which has 2 or more pairs of serial data circuits or an internal terminating resistor, in the direction of the open circuit.
  5. Ignition OFF and all vehicle systems OFF, key out of the ignition switch, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for greater than 130 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 130 ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: An open/high resistance on the serial data circuit between 2 control modules or splice packs, if equipped. An open/high resistance on the serial data circuit between a control module and a terminating resistor. An open/high resistance terminating resistor.

Perform the Diagnostic Repair Verification after completing the diagnostic repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Mid Speed GMLAN Serial Data (+)1U0100-U0299*1
Mid Speed GMLAN Serial Data (-)1U0100-U0299*1
Ground (DLC, terminal 5)1
* No communications with one or more mid speed GMLAN modules. An open in only one mid speed GMLAN serial data circuit may allow degraded communication between the modules. An open between the data link connector (DLC) and the first splice will only effect the communication with the scan tool. The vehicle modules will still communicate. 1. No communication on any mid speed GMLAN module.

Modules connected to the mid speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The mid speed GMLAN serial data bus uses a terminating resistor that is in parallel with the mid speed GMLAN (+) and (-) circuits.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they're transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. Do not replace a control module reporting a U code. The U code identifies which control module needs to be diagnosed for a communication issue.
  3. Communication may be available between the BCM and the scan tool with the mid speed GMLAN serial data system inoperative. This condition is due to the BCM using the high, mid, and low speed GMLAN systems.
  4. An open in the DLC ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle.
  5. The engine will not start when there is a total malfunction of the mid speed GMLAN serial data bus.
  6. Technicians may find various Local Area Network communication Diagnostic Trouble Codes (DTC) and no low speed GMLAN communications with the scan tool. These conditions may be caused by the installation of an aftermarket navigation radio module (see bulletins). Some customers may comment of one or more of the following concerns: Vehicle will not crank Vehicle cranks but will not start Vehicle stability enhancement system warning lights and messages PRNDL gear indicator position errors

Schematic Reference

  1. «Data Communication Schematics»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Note. Each control module may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following: Control modules the vehicle is equipped with Mid speed GMLAN serial data circuit terminating resistors Control module locations on the mid speed GMLAN serial data circuits Each control module's mid speed GMLAN serial data circuit terminals

  1. Attempt to communicate with all control modules on the mid speed GMLAN serial data circuit. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) . Communications should not be available with two or more control modules on the mid speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only. Refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) .
  2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
  3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuits listed below and ground: Terminal 3 Terminal 11 If greater than the specified range, test the serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to Voltage.
  5. Ignition OFF for 60 seconds, test for greater than 100 ohms between the serial data circuits listed below and ground: Terminal 3 Terminal 11 If not the specified value, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to ground.
  6. Test for 50-70 ohms between the serial data circuits terminal 3 and terminal 11. If less than 35 ohms, test for a short between the serial data circuits. Refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance. Refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, test the serial data circuits between the DLC and the first connection to the serial data circuit for an open/high resistance.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the mid speed GMLAN serial data circuits at an easily accessible control module.
  2. Ignition ON, test for greater than 4.5 V between each serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was disconnected.
  3. Ignition OFF, disconnect the harness connectors with the mid speed GMLAN serial data circuits at another control module, in the direction of the circuit shorted to voltage.
  4. Ignition ON, test for greater than 4.5 V between the serial data circuits at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are greater than 4.5 V. If all serial data circuits are less than the specified range, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to voltage on the serial data circuit between 2 control modules or splice packs, if equipped A short to voltage on the serial data circuit between a control module and a terminating resistor

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the harness connectors with the mid speed GMLAN serial data circuits at an easily accessible control module.
  2. Ignition OFF for 60 seconds, test for less than 1k ohms between each serial data circuit at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are less than 1k ohms. If all serial data circuits are greater than the specified range, replace the control module that was disconnected.
  3. Disconnect the harness connectors with the mid speed GMLAN serial data circuits at another control module, in the direction of the circuit shorted to ground.
  4. Ignition OFF for 60 seconds, test for less than 1k ohms between the serial data circuits at the control module connector that was just disconnected and ground. Verify that one or more serial data circuits are less than 1k ohms. If greater than the specified range for all serial data circuits, replace the control module that was just disconnected.
  5. Repeat step 3 until one of the follow conditions are isolated: A short to ground on the serial data circuit between 2 control modules or splice packs, if equipped A short to ground on the serial data circuit between a control module and a terminating resistor

Testing the Serial Data Circuits for a Short between the Circuits

  1. Ignition OFF, disconnect the harness connectors with the mid speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
  2. Ignition OFF for 60 seconds, test for less than 35 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are less than 35 ohms. If each pair of serial data circuits is greater than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Disconnect the harness connectors with the mid speed GMLAN serial data circuits at another control module, in the direction of the circuits shorted together.
  5. Ignition OFF for 60 seconds, test for less than 35 ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are less than 35 ohms. If each pair of serial data circuits is within the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: Serial data circuits shorted together between 2 control modules or splice packs, if equipped Serial data circuits shorted together between a control module and a terminating resistor A shorted terminating resistor

Testing the Serial Data Circuits for an Open/High Resistance

  1. Ignition OFF, disconnect the harness connectors with the mid speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
  2. Ignition OFF for 60 seconds, test for greater than 100k ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 100k ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
  3. Connect the harness connectors at the control module that was disconnected.
  4. Disconnect the harness connectors with the mid speed GMLAN serial data circuits at another control module, in the direction of the open circuit.
  5. Ignition OFF for 60 seconds, test for greater than 100k ohms between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits is greater than 100k ohms. If each pair of serial data circuits is less than the specified range, replace the control module that was just disconnected.
  6. Repeat step 3 until one of the following conditions are isolated: An open/high resistance on the serial data circuit between 2 control modules or splice packs, if equipped An open/high resistance on the serial data circuit between a control module and a terminating resistor An open/high resistance terminating resistor

Perform the Diagnostic Repair Verification after completing the repair.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control module replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Low Speed GMLAN Serial Data1U0100-U0299*1
Ground (DLC, terminal 5)1*
* An open between the data link connector serial data circuit terminal 1 or ground circuit terminal 5 and the BCM circuit will only effect the communication with the scan tool. 1. No communication on any low speed GMLAN module

The serial data is transmitted over a single wire to the appropriate control modules. The transmission speed for GMLAN low speed is up to 83.33 Kb/s. Under normal vehicle operating conditions, the speed of the buss is 33.33 Kb/s. The control modules toggle the serial data circuit between 0-5 V during normal communications. To wake the control modules connected to the GMLAN low speed serial data circuit, a voltage wake up pulse of 10 V is sent out. If serial data is lost, control modules will set a no communication code against the non-communicating control module. A loss of serial data communications DTC does not represent a failure of the module that set it.

  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more modules was interrupted during diagnosis A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  3. Communication may be available between the body control module (BCM) and the scan tool with the low speed GMLAN serial data system inoperative. This condition is due to the BCM using both the high and low speed GMLAN systems.
  4. An open in the low speed GMLAN serial data circuit between the splice pack and a module will only affect that specific module. This type of failure will set a loss of communication DTC for each module effected, and the other modules will still communicate.
  5. An open in the data link connector (DLC) ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle.
  6. The engine may not start when there is a total malfunction of the low speed GMLAN serial data circuit.
  7. Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC) and no low speed LAN communications with the scan tool. These conditions may be caused by the installation of an aftermarket navigation radio module (see bulletins). Some customers may comment of one or more of the following concerns: Vehicle will not crank Vehicle cranks but will not start Vehicle stability enhancement system warning lights and messages PRNDL gear indicator position errors

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Note. Use the schematic to identify the following: Control modules the vehicle is equipped with Control module and splice pack locations on the low speed GMLAN serial data circuit The low speed GMLAN serial data circuit terminals for each control module, component, or splice pack

  1. Attempt to communicate with all control modules on the low speed GMLAN serial data circuit. Refer to «Data Link References»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system__data-link-references) . Communications should not be available with two or more control modules on the low speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only. Refer to «DTC U0100-U02FF (without HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) , «DTC U0100-U02FF (with HP6)»(/buick/regal/v-2009-2013/remont/communication-devices/#data-communications-system) . If one or more control modules are communicating but not all, refer to Testing the Serial Data Circuit for an Open/High Resistance.
  2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
  3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuit terminal 1 and ground. If greater than the specified range, test the serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuit for a Short to Voltage.
  5. Ignition OFF for 60 seconds, test for greater than 100 ohms between the serial data circuit terminal 1 and ground. If less than the specified range, test the serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to ground.
  6. Disconnect the harness connector at the first splice pack closest in the circuit to the DLC.
  7. Test for less than 2 ohms between the DLC serial data circuit terminal 1 and the splice pack connector serial data input terminal. If greater than the specified range, test the serial data circuit for an open/high resistance. If the circuit tests normal, replace the splice pack.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the appropriate harness connectors at the following components: All low speed serial data splice packs Any module or component between that may be between the splice packs
  2. Ignition ON, test for less than 4.5 V between the DLC serial data circuit terminal 1 and ground. If greater than the specified range, repair the short to voltage.
  3. Test for less than 4.5 V between each serial data circuit at each component connector and ground. If greater than the specified range, perform the appropriate test listed below: Serial data circuits with one control module, test the serial data circuit for a short to voltage. If the circuit tests normal, replace the control module. Serial data circuits with 2 or more control modules, test each section of the serial data circuit for a short to voltage. If the circuits test normal, replace the control module that causes the short to voltage when connected.

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the appropriate harness connectors at the following components: All low speed serial data splice packs Any module or component between that may be between the splice packs
  2. Test for infinite resistance between the DLC serial data circuit terminal 1 and ground. If not the specified value, repair the short to ground.
  3. Ignition OFF for 60 seconds, test for greater than 100 ohms between each serial data circuit at the splice pack and ground. If less than the specified range, perform the appropriate test listed below: Serial data circuits with one control module, test the serial data circuit for a short to ground. If the circuit tests normal, replace the control module. Serial data circuits with 2 or more control modules, test each section of the serial data circuit for a short to ground. If the circuits test normal, replace the control module that causes the short to ground when connected.

Testing the Serial Data Circuit for an Open/High Resistance

  1. If equipped with a second splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the second splice pack. If all control modules on the second splice pack do not communicate, test the serial data circuit between the first and second splice packs for an open/high resistance. If the circuit tests normal, test the second splice pack for an open/high resistance. If the splice pack tests normal, replace any module or component that may be between those two splice packs.
  2. If equipped with a third splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the third splice pack. If all control modules on the third splice pack do not communicate, test the serial data circuit between the second and third splice packs for an open/high resistance. If the circuit tests normal, test the third splice pack for an open/high resistance. If the splice pack tests normal, replace any module or component that may be between the those two splice packs.
  3. Ignition OFF, disconnect the splice pack containing the serial data circuits to the modules that are not communicating.
  4. Install a 3 A fused jumper wire between the splice pack connector serial data input terminal and a low speed GMLAN serial data circuit that is not communicating
  5. Ignition ON, verify the scan tool communicates with the control modules connected to the low speed GMLAN serial data circuit. If any control module does not communicate, test each section of the serial data circuit for an open/high resistance. If the circuits test normal, replace the control module that does not communicate when connected.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, programming and setup

Data Link References

This table identifies which serial data link that a particular module uses for in-vehicle data transmission. Some modules may use more than one data link to communicate. Some modules may have multiple communication circuits passing through them without actively communicating on that data link. This table is used to assist in correcting a communication malfunction. Not all modules listed will be applicable to all vehicles. Refer to the schematics to determine which modules apply. For the description and operation of these serial data communication circuits refer to Data Link Communications Description and Operation .

Control ModuleData Link TypeDiagnostic Procedure
Schematic Reference: Data Communication Schematics
Body Control ModuleHigh Speed GMLAN Low Speed GMLAN Local Interconnect Network (LIN)Scan Tool Does Not Communicate with High Speed GMLAN Device Scan Tool Does Not Communicate with Low Speed GMLAN Device DTC U1500-U15BF
Electronic Brake Control ModuleHigh Speed GMLAN Chassis High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device Scan Tool Does Not Communicate with Chassis High Speed GMLAN Device
Engine Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Fuel Pump Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
HVAC Control ModuleLow Speed GMLAN Local Interconnect Network (LIN)Scan Tool Does Not Communicate with Low Speed GMLAN Device DTC U1500-U15BF
HVAC ControlsLocal Interconnect Network (LIN)DTC U1500-U15BF
Inflatable Restraint Sensing and Diagnostic ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Info Display ModuleLocal Interconnect Network (LIN)DTC U1500-U15BF
Instrument ClusterLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Multi-axis Acceleration SensorChassis High Speed GMLANScan Tool Does Not Communicate with Chassis High Speed GMLAN Device
Multimedia Player Interface ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Parking Brake Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Passenger Presence Detection ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Power Steering Control ModuleHigh Speed GMALNScan Tool Does Not Communicate with High Speed GMLAN Device
RadioMid Speed GMLAN Low Speed GMLANScan Tool Does Not Communicate with Mid Speed GMLAN Device Scan Tool Does Not Communicate with Low Speed GMLAN Device
Radio ControlsLocal Interconnect Network (LIN)DTC U1500-U15BF
Radio Control Multi-Function SwitchLocal Interconnect Network (LIN)DTC U1901
Rear Parking Assist Control ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Seat Heating Control ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Steering Wheel Angle SensorChassis High Speed GMLANScan Tool Does Not Communicate with Chassis High Speed GMLAN Device
Sunroof MotorLocal Interconnect Network (LIN)DTC U1500-U15BF
Suspension Control ModuleHigh Speed GMLAN Chassis High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device Scan Tool Does Not Communicate with Chassis High Speed GMLAN Device
Telematics Communication Interface Control ModuleHigh Speed GMLAN Low Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device Scan Tool Does Not Communicate with Low Speed GMLAN Device
Transmission Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Transmission Shift Lever Position IndicatorLocal Interconnect Network (LIN)DTC U1500-U15BF
Window Motor - DriverLocal Interconnect Network (LIN)DTC U1500-U15BF
Window Motor - PassengerLocal Interconnect Network (LIN)DTC U1500-U15BF
Window Switch - DriverLocal Interconnect Network (LIN)DTC U1500-U15BF
Window Switch - Left RearLocal Interconnect Network (LIN)DTC U1500-U15BF
Window Switch - Right RearLocal Interconnect Network (LIN)DTC U1500-U15BF

Data Link References

Scheme 12

Scheme 12: Body Control Module Replacement (Left Hand Drive)
Scheme 12: Body Control Module Replacement (Left Hand Drive)
CalloutComponent Name
Preliminary Procedure Remove the instrument panel lower trim panel- left side. Refer to Instrument Panel Lower Trim Panel Replacement - Left Side .
1Inner Electrical Center Procedure Disconnect the lower three electrical connectors on the body control module. Clip out the inner electrical center.
2Body Control Module Procedure Disconnect the upper four electrical connectors on the body control module. Pull out the body control module of the bracket. For programming and set up information, refer to Control Module References .

Body Control Module Replacement (Left Hand Drive)

Scheme 13

Scheme 13: Body Control Module Bracket Replacement
Scheme 13: Body Control Module Bracket Replacement
CalloutComponent Name
Preliminary Procedures Remove the body control module. Refer to Body Control Module Replacement (Left Hand Drive) . Remove the headlamp control module. Refer to Headlamp Control Module Replacement . Remove the floor air outlet duct - left side. Refer to Floor Air Outlet Duct Replacement - Left Side .
1Body Control Module Bracket Fastener (Qty: 3) CAUTION: Refer to Fastener Caution . Tighten 9 N.m (80 lb in)
2Body Control Module Bracket
CAUTION
Refer to Fastener Caution .

Body Control Module Bracket Replacement

Body Control System Description and Operation

The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the BCM. The BCM also has discrete input and output terminals to control the vehicle's body functions. The BCM is wired to the high speed GMLAN serial data bus, low speed GMLAN serial data bus and Multiple LIN buses and acts as a gateway between them.

Power Mode Master

This vehicle body control module (BCM) functions as the power mode master (PMM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determining the power mode that will be sent over the serial data circuits to the other modules that need this information; the PMM will activate relays and other direct outputs of the PMM as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.

Gateway

The body control module (BCM) in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed bus and the GMLAN low speed bus for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.

All communication between the BCM and a scan tool is on the high speed GMLAN serial data circuits. A lost communication DTC typically is set in modules other than the module with a communication failure.

Body Control

The various body control module (BCM) input and output circuits are illustrated in the corresponding functional areas on the BCM electrical schematics. Refer to the Body Control System Schematics for more detailed information.

Data Link Communications Description and Operation

Note. This is an overview of different serial data buses used by GM control modules to communicate with each others. Use Data Communication Schematics to find out which serial data buses are configured for a specific vehicle.

There are many components in a vehicle that rely on information from other sources, transmit information to other sources, or both. Serial data communication networks provide a reliable, cost effective, way for various components of the vehicle to "talk" to one another and share information.

GM uses a number of different communication buses to insure the timely and efficient exchange of information between control modules. When compared to each other, some of these buses are different in nature as far as speed, signal characteristics, and behavior. An example of this is the High Speed GMLAN and Low Speed GMLAN buses.

On the other hand, when other buses are compared to each other they have similar characteristics and simply operate in parallel. In this case they are used to group together components which have high interaction. Examples are the High Speed GMLAN, Powertrain Expansion, and Chassis Expansion buses. This allows them to communicate with each other on a bus with reduced message congestion insuring faster and the more timely exchange of information than if all vehicle control modules were on a single bus.

The majority of information that exists within a given network generally stays local; however some information will have to be shared on other networks. Control modules designated as Gateway's perform the function of transferring information between the various buses. A Gateway module is connected to at least 2 buses and will interact with each network according to its message strategy and transmission models.

GMLAN provides the capability for a receiving control module to monitor message transmissions from other control modules in order to determine if messages of interest are not being received. The primary purpose is to allow reasonable default values to be substituted for the information no longer being received. Additionally, a control module may set a Diagnostic Trouble Code to indicate that the control module it is expecting information from is no longer communicating.

High Speed GMLAN Circuit Description

A High Speed GMLAN Bus is used where data needs to be exchanged at a high enough rate to minimize the delay between the occurrence of a change in sensor value and the reception of this information by a control device using the information to adjust vehicle system performance.

The High Speed GMLAN serial data network consists of two twisted wires. One signal circuit is identified as GMLAN-High and the other signal circuit is identified as GMLAN-Low. At each end of the data bus there is a 120 ohms termination resistor between the GMLAN-High and GMLAN-Low circuits.

Data symbols (1's and 0's) are transmitted sequentially at a rate of 500 Kbit/s. The data to be transmitted over the bus is represented by the voltage difference between the GMLAN-High signal voltage and the GMLAN-Low signal voltage.

When the two wire bus is at rest the GMLAN-High and GMLAN-Low signal circuits are not being driven and this represents a logic "1". In this state both signal circuits are at the same voltage of 2.5 V. The differential voltage is approximately 0 V.

When a logic "0" is to be transmitted, the GMLAN-High signal circuit is driven higher to about 3.5 V and the GMLAN-Low circuit is driven lower to about 1.5 V. The differential voltage becomes approximately 2.0 (+/- 0.5) V.

Chassis High Speed GMLAN Circuit Description

The GMLAN Chassis Expansion Bus is basically a copy of the High Speed GMLAN Bus except that its use is reserved for chassis components. This implementation splits message congestion between two parallel buses helping to insure timely message transmission and reception. Sometimes communication is required between the Chassis Expansion Bus and the primary High Speed GMLAN Bus. This is accomplished by using the Electronic Brake Control Module (EBCM) as the Gateway module. Since the High Speed GMLAN Chassis Expansion Bus and primary High Speed GMLAN Bus operate in the same manner, the diagnostics for each are similar.

CAN Graphical Interface (CGI) Circuit Description

This bus is used by the Entertainment sub-system to transfer high-rate display graphics between the Radio and the Info Display Module and/or Radio/HVAC Control. The electrical characteristics of the CAN Graphical Interface (CGI) Bus are very similar to the High Speed GMLAN Bus. The message strategy and construction of messages are different however. Sometimes communication is required between the CAN Graphical Interface Bus and the Low Speed GMLAN Bus. This is accomplished by using the Radio SilverBox as the Gateway module. Since the CAN Graphical Interface Bus and primary High Speed GMLAN Bus have similar electrical characteristics, the diagnostics for each are similar.

In the case where the Info Display Module and Radio/HVAC Control are separate control modules the Info Display Module is responsible for passing information between the Radio and the Radio/HVAC Control. The Radio interfaces only with the Info Display Module and the Info Display Module then communicates with the Radio/HVAC Control through a Local Interconnect Network (LIN) interface.

A bus wake up signal will be generated by the Radio or by the Info Display Module when the system functionality is required. The communication function of the CAN Graphical Interface shall be enabled or disabled based on the voltage level of the Center Stack Wake. The network will stay awake as long as the circuit voltage is driven low, to less than 1.5 V. Communications are disabled with a high circuit voltage around 5.0 V.

The Radio can execute a warm reset of the Info Display Module if the Info Display Module fails to respond to the Radio's request. The Center Stack Reset is a low-asserted pull down output (less than 1.5 V) from the Radio to the Info Display Module and has the same electrical characteristics as those for the Center Stack Wake signal defined above.

Mid Speed GMLAN Circuit Description

The Mid Speed GMLAN Bus is very similar to the High Speed GMLAN Bus except that it uses a slower transmission rate of 125 Kbit/s. This bus is intended for use where the system response time demands that a large amount of data be transmitted in a relatively short amount of time, such as updating a graphics display. As such it has usually been used for infotainment applications. Sometimes communication is required between the Low Speed GMLAN Bus and the Mid Speed GMLAN Bus. This is accomplished by using the Radio (Silverbox) as the Gateway module. Since the Mid Speed GMLAN Bus and primary High Speed GMLAN Bus operate in a similar manner, the diagnostics for each are similar.

Low Speed GMLAN Circuit Description

Low Speed GMLAN Bus is used in applications where a high data rate is not required which allows for the use of less complex components. It is typically used for operator controlled functions where the response time requirements are slower than those required for dynamic vehicle control.

The Low Speed GMLAN Serial Data Network consists of a single wire, ground referenced bus with high side voltage drive. During on road vehicle operation data symbols (1's and 0's) are transmitted sequentially at the normal rate of 33.3 Kbit/s. For component programming only, a special high speed data mode of 83.3 Kbit/s may be used.

Unlike the high speed dual wire networks, the single wire low speed network does not use terminating resistors at either end of the network.

The data symbols to be transmitted over the bus are represented by different voltage signals on the bus. When the Low Speed GMLAN Bus is at rest and is not being driven, there is a low signal voltage of approximately 0.2 V. This represents a logic "1". When a logic "0" is to be transmitted, the signal voltage is driven higher to around 4.0 V or higher.

Local Interconnect Network (LIN) Circuit Description

The Local Interconnect Network (LIN) Bus consists of a single wire with a transmission rate of 10.417 Kbit/s. This bus is used to exchange information between a master control module and other smart devices which provide supporting functionality. This type of configuration does not require the capacity or speed of either a High Speed GMLAN Bus or Low Speed GMLAN Bus and is thus relatively simpler.

The data symbols (1's and 0's) to be transmitted are represented by different voltage levels on the communication bus. When the LIN Bus is at rest and is not being driven, the signal is in a high voltage state of approximately Vbatt. This represents a logic "1". When a logic "0" is to be transmitted, the signal voltage is driven low to about ground (0.0 V).

Communication Enable Circuit Description

Control modules on GMLAN high speed type networks, excluding the Mid Speed GMLAN Bus and CAN Graphical Interface Bus, enable or disable communication based on the voltage level of this circuit. When the circuit voltage is high (around 12 V), communications are enabled. When the circuit is low, communications are disabled.

The CAN Graphical Interface Bus is similar but uses different voltage levels. See description above for the CAN Graphical Interface Bus.

Data Link Connector (DLC)

The data link connector (DLC) is a standardized 16-cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following

  1. Pin 1 Low speed GMLAN communications terminal
  2. Pin 2 Class 2 communications terminal
  3. Pin 3 Mid speed GMLAN serial bus (+) terminal
  4. Pin 4 Scan tool power ground terminal
  5. Pin 5 Common signal ground terminal
  6. Pin 6 High speed GMLAN serial data bus (+) terminal
  7. Pin 7 Keyword communications terminal
  8. Pin 11 Mid speed GMLAN serial bus (-) terminal
  9. Pin 12 Chassis high speed GMLAN serial bus (+) terminal
  10. Pin 13 Chassis high speed GMLAN serial bus (-) terminal
  11. Pin 14 High speed GMLAN serial data bus (-) terminal
  12. Pin 16 Scan tool power, battery positive voltage terminal

Serial Data Reference

The scan tool communicates over the various buses on the vehicle. When a scan tool is installed on a vehicle, the scan tool will try to communicate with every control module that could be optioned into the vehicle. If an option is not installed on the vehicle, the scan tool will display No Comm for that optional control module. In order to avert misdiagnoses of No Communication with a specific control module, refer to Data Link References for a list of control modules, the buses they communicate with, and the RPO codes for a specific control module.

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Diagnostic Repair Verification
• Control Module References
• COMPONENT CONNECTOR END VIEWS -- INDEX
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Diagnostic Trouble Code (DTC) List - Vehicle
• GMLAN Wiring Repairs
• High Voltage Disabling
• Radio/Navigation System Schematics
• Radio/Audio System Description and Operation
• Checking Aftermarket Accessories
• Instrument Panel Lower Trim Panel Replacement - Left Side
• Headlamp Control Module Replacement
• Floor Air Outlet Duct Replacement - Left Side
• Fastener Caution
• Power Mode Description and Operation
• Control Module U Code List
• DTC B1000
• Data Link Communications Description and Operation
• Symptoms - Data Communications
• Data Link References

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