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Contents Wiring diagrams Section: Communication Devices All sections

Data Communication System Chevrolet Malibu VII

Communication Devices 8 illustrations ~9996 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Body Control Module Bolt Screw1.5 N.m13 lb in

Scheme 1

Scheme 1: Data Communication Schematics
Scheme 1: Data Communication Schematics

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

Scheme 4

Scheme 4: Body Control System Schematics
Scheme 4: Body Control System Schematics

Scheme 5

Scheme 5
Scheme 5

Scheme 6

Scheme 6
Scheme 6

Scheme 7

Scheme 7
Scheme 7

DIAGNOSTIC CODE INDEX

DTCDescription
DTC B1000B1000 00: Electronic Control Unit (ECU) Performance No Additional Information Available B1000 04: Side Object Detection Performance - RAM Failure B1000 08: Electronic Control Unit (ECU) Performance Signal Invalid B1000 12: Electronic Control Unit (ECU) Performance Below Minimum Threshold B1000 31: Electronic Control Unit (ECU) General Checksum Problem B1000 32: Electronic Control Unit (ECU) General Memory Failure B1000 33: Electronic Control Unit (ECU) Performance Special Memory Failure B1000 34: Electronic Control Unit (ECU) Performance RAM Integrity B1000 35: Electronic Control Unit (ECU) Performance ROM Integrity B1000 36: Electronic Control Unit (ECU) Performance EEPROM Integrity B1000 37: Electronic Control Unit (ECU) Performance Watchdog / Safety Failure B1000 38: Electronic Control Unit (ECU) Performance Supervision Software Failure B1000 39: Electronic Control Unit (ECU) Performance Internal Electronic Failure B1000 43: Electronic Control Unit (ECU) Performance EEPROM Error B1000 46: Side Object Detection Performance - Invalid Configuration B1000 56: Electronic Control Unit (ECU) Performance Allowable Number of Transitions / Events Exceeded B1000 57: Electronic Control Unit (ECU) Performance B1000 73: Electronic Control Unit (ECU) Performance Parity Error B1000 0F: Electronic Control Unit (ECU) Performance Erratic B1000 2B: Electronic Control Unit (ECU) Performance Missing Reference B1000 2C: Electronic Control Unit Performance Reserved B1000 3B: Electronic Control Unit (ECU) Performance Internal Self Test Failed B1000 3C: Electronic Control Unit (ECU) Performance Internal Communications Failure B1000 4A: Side Object Detection Performance - PROM Checksum Error B1000 F0: Side Object Detection RF Transmit Chain Failed B1000 F1: Side Object Detection RF Receive Chain Failed B1000 F2: Side Object Detection Frequency Calibration Failure B1000 F3: Side Object Detection Inter-Processor Communication Failed
DTC B1001B1001 00: Option Configuration Error B1001 45: Option Configuration Error Variant Not Programmed B1001 46: Option Configuration Error B1001 4B: Option Configuration Error Calibration Not Learned
DTC B1004B1004: Keep Alive Memory (KAM) Reset
DTC B1009B1009: EEPROM Checksum Mismatch/Error
DTC C0550C0550 XX: Electronic Control Unit
DTC U0001U0001 00: High Speed CAN Communication Bus
DTC U0020U0020 00: Low Speed CAN Communication Bus Performance
DTC U0073 or U2100U0073 00: Control Module Communication Bus Off U0073 71: ECU HS Bus Off U0073 72: ECU LS Bus Off U2100 00: Controller Area Network (CAN) Bus Communication U2100 47: Controller Area Network (CAN) Bus Communication
DTC U0100-U02FFMessage including transmitter module availability has not been received
DTC U2103U2103 00: Fewer Controllers On Than Programmed
DTC U2105-U2199U2105 00: Lost Communication With Engine Control System U2106 00: Lost Communication With Transmission Control System U2107 00: Lost Communication With Body Control System U2108 00: Lost Communication With ABS/TCS Control System U2109 00: Lost Communication With Powertrain Control System U2110 00: Lost Communication With Chassis Multiple Control System U2111 00: Lost Communication With Steering Control System U2112 00: Lost Communication With Electronic Suspension Control (ESC) U2113 00: Lost Communication With Sensing and Diagnostic Module (SDM) U2114 00: Lost Communication With PPS or CPS U2115 00: Lost Communication With (Restraints Control System) U2116 00: Lost Communication With Instrument Panel Cluster (IPC) U2117 00: Lost Communication With Driver Information Center (DIC) U2118 00: Lost Communication With Head Up Display (HUD) U2119 00: Lost Communication With Daytime Running Lamps (DRL) System U2120 00: Lost Communication With Automatic Headlamp Leveling Device (AHLD) U2121 00: Lost Communication With Radio Display U2122 00: Lost Communication With Radio U2123 00: Lost Communication With Compact Disc Changer (CDX) U2124 00: Lost Communication With Audio Amplifier U2125 00: Lost Communication With Telematic Unit U2126 00: Lost Communication With (Mobile Communications Control System) U2127 00: Lost Communication With Front HVAC U2128 00: Lost Communication With Rear HVAC U2129 00: Lost Communication With Remote Function Actuator (RFA) U2130 00: Lost Communication With Driver Door Module (DDM) U2131 00: Lost Communication With Driver Seat Module (DSM) U2132 00: Lost Communication With Passenger Door Module (PDM) U2133 00: Lost Communication With Passenger Seat Module (PSM) U2134 00: Lost Communication With Rear Door Module (RDM) U2135 00: Lost Communication With Rear Integration Module (RIM) U2136 00: Lost Communication With Memory Mirror Module (MMM) U2137 00: Lost Communication With Vehicle Theft Deterrent (VTD) U2138 00: Lost Communication With Column Locking Module (CLM) U2139 00: Lost Communication With Column Integration Module (CIM) U2140 00: Lost Communication With Underhood Electrical Center (UEC) U2141 00: Lost Communication With Rear Electrical Center (REC) U2142 00: Lost Communication With Yaw Rate Sensor (YRS) U2143 00: Lost Communication With Steering Angle Sensor (SAS) U2144 00: Lost Communication With Distance Sensing Cruise Control Module U2145 00: Lost Communication With Parking Assistance System (PAS) U2146 00: Lost Communication With Shift Lever Module (SLM) U2147 00: Lost Communication With Auxiliary Heater System (AHS) U2148 00: Lost Communication With Sun Roof Module (SRM) U2149 00: Lost Communication With Tire Pressure Monitor (TPM) System U2150 00: Navigation Electronic Control Unit (ECU) Gateway Communications U2151 00: Navigation Electronic Control Unit (ECU) Communications U2152 00: Navigation Bus Request Line Circuit Low U2153 00: Navigation Electronic Control Unit (ECU) - VICS Communication Circuit U2160 00: Lost Communication With Steering Control System Sensor U2161 00: Lost Communication With Dash Integration Module (DIM) U2162 00: Lost Communication With Instrument Panel integration Module (IPM) U2163 00: Lost Communication With Left Rear Door Module (LRDM) U2164 00: Lost Communication With Right Rear Door Module (RRDM) U2165 00: Lost Communication With Driver Door Switch (DDS) U2166 00: Lost Communication With Driver Position Module (DPM) U2167 00: Lost Communication With Remote Control Door Lock Receiver U2168 00: Lost Communication With Side Object Detection (SOD) Module - Left U2169 00: Lost Communication With Side Object Detection (SOD) Module - Right U2170 00: Lost Communication With Four Wheel Drive (4WD) Clutch U2171 00: Lost Communication With Rear Seat Entertainment (RSE) U2172 00: Lost Communication With Digital Radio Receiver U2173 00: Lost Communication With Passive Entry and Passive Start System U2174 00: Lost Communication With Parking Heater System U2175 00: Lost Communication With Special Vehicle Module U2176 00: Lost Communication With Power Take Off (PTO) Control Module U2177 00: Lost Communication With Cruise Control Module U2178 00: Lost Communication With Trailer Interface Module U2179 00: Lost Communication With Television Module U2180 00: Lost Communication With Folding Top Control Module U2181 00: Lost Communication With Moveable Roof Module

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
U0002 00High Speed CAN Bus
U0010 00Medium Speed CAN Bus
U0020 00Low Speed CAN Bus
U0073 00Control Module Communication Bus A Off
U0073 71ECU HS Bus Off
U0073 72ECU LS Bus Off
U0074 00Control Module Communication Bus B Off
U0075 00Control Module Communication Bus C Off
U0100 00Lost Communication with Engine/Powertrain Control Module (ECM/PCM)
U0100 75Lost Communication with Engine/Powertrain Control Module (ECM)
U0100 7FLost Communication with Engine/Powertrain Control Module (ECM)
U0101 00Lost Communication with Transmission Control Module (TCM)
U0101 75Lost Communication with Transmission Control Module (TCM)
U0102 00Lost Communication with Transfer Case Control Module
U0104 00Lost Communication with Cruise Control Module
U0104 7FLost Communication with Cruise Control Module
U0106 00Lost Communication with Glow Plug Control Module
U0109 00Lost Communication with Fuel Pump Control Module
U010E 00Lost Communication with Reductant Sensor Module
U010F 00Lost Communication with Air Conditioning Control Module
U0111 00Lost Communication with Battery Energy Control Module
U0115 00Lost Communication with ECM/PCM B
U0117 00Lost Communication PTO Control Module
U0121 00Lost Communication with Electronic Brake Control Module (EBCM)
U0122 00Lost Communication with Vehicle Stability Control Module (ESCM)
U0123 00Lost Communication with Yaw Rate Sensor Module
U0126 00Lost Communication with Steering Wheel Angle Sensor Module
U0128 00Lost Communication with Park Brake Control Module
U0129 00Lost Communication with Brake System Control Module
U0131 00Lost Communication with Power Steering Control Module
U0132 00Lost Communication with Suspension Control Module
U0134 00Lost Communication with Power Steering Control Module - Rear
U0136 00Lost Communication with Differential Control Module - Rear
U0137 00Lost Communication with Trailer Brake Control Module
U0140 00Lost Communication with Body Control Module
U0141 00Lost Communication with Body Control Module A
U0144 00Lost Communication with Body Control Module D
U0146 00Lost Communication with Gateway A
U0151 00Lost Communication with Inflatable Restraint Sensing and Diagnostic Module (SDM)
U0151 71Lost Communication with Inflatable Restraint Sensing and Diagnostic Module (SDM) Invalid Serial Data Received
U0151 7FLost Communication with Restraints Control Inflatable Restraint Sensing and Diagnostic Module (SDM) Erratic
U0155 00Lost Communication with Instrument Panel Cluster (IPC) Control Module
U0156 00Lost Communication with Information Center A (DIC)
U0157 00Lost Communication with Information Center B (DID)
U0158 00Lost Communication with Head Up Display
U0159 00Lost Communication with Parking Assist Control Module (RPA)
U0160 00Lost Communication with Chime Alarm Control Module
U0164 00Lost Communication with HVAC Control Module
U0165 00Loss of Communication with HVAC Control Module - Rear
U0166 00Lost Communication with Auxiliary Heater Control Module
U0168 00Lost Communication with Vehicle Security Control Module
U0170 00Lost Communication with Restraints System Sensor A (PPS)
U0172 00Lost Communication with Restraints System Sensor C
U0173 00Lost Communication with Restraints System Sensor D
U0181 00Lost Communication with Headlamp Leveling Control Module
U0184 00Lost Communication with Radio
U0186 00Lost Communication with Audio Amplifier
U0191 00Lost Communication with Television
U0194 00Lost Communication with Digital Radio Receiver (DRR)
U0196 00Lost Communication with Rear Audio Control Module
U0198 00Lost Communication with Telematic Control Module
U0199 00Lost Communication with Driver Door Control Module
U0200 00Lost Communication with Door Control Module
U0208 00Lost Communication with Seat Control Module A (DSM/MSM)
U0209 00Lost Communication with Seat Control Module B (HVSM)
U0210 00Lost Communication with Seat Control Module C (RHSM)
U0214 00Lost Communication with Remote Function Actuation
U0230 00Lost Communication with Rear Gate Module
U0232 00Lost Communication with Side Object Detection (SOD) Module - Left
U0233 00Lost Communication with Side Object Detection (SOD) Module - Right
U0236 00Lost Communication with Column Locking Module (CLM)
U023A 00Lost Communication with Vehicle Direction Camera Control Module (Lane Departure Warning)
U0241 00Lost Communication with Headlamp Control Module A
U0249 00Loss of Communication with Entertainment Control Module - Rear B
U0252 00Lost Communication with Trailer Interface Module
U0255 00Loss of Communication with Front Display Interface Module
U0256 00Loss of Communication with Front Controls Interface Module
U0257 00Loss of Communication with Front Controls/Display Interface Module
U0293 00Lost Communication with HP2 Powertrain Control Module
U029D 00Lost Communication with NOX Sensor Module 1
U029E 00Lost Communication with NOX Sensor Module 2
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 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
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
U180FElectronic Brake Control Module Communications Bus B OFF
U1000Class 2 Data Link Malfunction
U1016Lost Communication with ECM/PCM
U1017Lost Communication with Engine Control System
U1024Lost Communication with Transmission Control Module
U1026Lost Communication with Transfer Case Control Module
U1040Lost Communication with Electronic Brake Control Module
U1041Lost Communication with Electronic Brake Control Module
U1064Lost Communication with Body Control Module/Dash Integration Module
U1088Lost Communication with Inflatable Restraint Sensing and Diagnostic Module
U1096Lost Communication with Instrument Panel Cluster
U1098Lost Communication with Secondary Information Center
U1099Lost Communication with Head Up Display
U1100Lost Communication with Driver Information and Displays Control System
U1128Lost Communication with Radio
U1129Lost Communication with Amplifier
U1133Lost Communication with Mini Disc Changer
U1137Lost Communication with Satellite Digital Audio Reception System (DRR)
U1153Lost Communication with Climate Control Panel
U1162Lost Communication with Liftgate Module
U1164Lost Communication with Driver Door Switch
U1165Lost Communication with Passenger Door Switch
U1176Lost Communication with Remote Function Actuation
U1177Lost Communication with Folding Top Controller
U1192Lost Communication with Immobilizer
U1193Lost Communication with Remote Control Door Lock Receiver
U1255Loss of Class 2 Communication
U1300Class 2 Data Link Low
U1301Class 2 Data Link High
U1305Class 2 Data Link High or Low
U1500 00Inter Device Dedicated Bus
U1500 00(EBCM) Inter Device Dedicated Bus (Lost Communication with Yaw and Lateral Accelerometer Sensor)
U1500 00(DDM/PDM) Inter Device Dedicated Bus (Lost Communication with Front Window Motor)
U1500 01Inter-Device Dedicated Bus Short to Battery
U1500 02Inter-Device Dedicated Bus Short to Ground
U1511 00(BCM) Inter-device Dedicated Bus 1 Lost Communication with Device 1 (Electronic Compass Module)
U1511 00(DDM/PDM) Inter-device Dedicated Bus 1 Lost Communication with Device 1 (Front Window Motor)
U1511 00(HCM) Inter-device Dedicated Bus 1 Lost Communication with Device 1 (AFL - Left)
U1512 00(DDM) Inter-device Dedicated Bus 1 Lost Communication with Device 2 (Left Rear Window Motor)
U1513 00(PDM) Inter-device Dedicated Bus 1 Lost Communication with Device 3 (Right Rear Window Motor)
U1521 00(HCM) Inter-device Dedicated Bus 2 Lost Communication with Device 1 (AFL - Right)
U1650 00Chassis System Dedicated Bus Controller
U1651 00Chassis System Dedicated Bus Sensor
U180F 00Control Module Communication Bus B Off
U1802 00Lost Communication with Fuel Pump Control Module
U1812 00Battery Energy Control Module Bus B High Speed Communication Enable Circuit Low
U1813 00Battery Energy Control Module Bus B High Speed Communication Enable Circuit High
U1814 00Powertrain High Speed Communication Enable Circuit
U1815 00Lost Communication with Drive Motor Control Module A on Bus B
U1816 00Lost Communication with Drive Motor Control Module B on Bus B
U1817 00Lost Communication with Hybrid Powertrain Control Module on Bus B
U1818 00Lost Communication with ECM/PCM A on Bus B
U1820 00Lost Communication with Brake System Control Module on Bus B
U1821 00Lost Communication with DC to DC Converter Control Module A on Bus B
U1822 00Lost Communications with Power Steering Control Module on Bus B
U1823 00Lost Communications with Cruise Control Module on Bus B
U1824 00Lost Communications with Suspension Control Module
U1825 00Lost Communications with Vehicle Dynamics Control Module
U1826 71Lost Communication with Multi-Axis Acceleration Sensor Module on Bus B Invalid Serial Data Received
U1826 72Lost Communication with Multi-Axis Acceleration Sensor Module on Bus B Alive Counter Incorrect/Not Updated
U1826 7FLost Communication with Multi-Axis Acceleration Sensor Module on Bus B Erratic
U1827 71Lost Communication with Steering Angle Sensor Module on Bus B Invalid Serial Data
U1827 72Lost Communication with Steering Angle Sensor Module on Bus B Alive Counter Incorrect/Not Updated
U1827 74Lost Communication with Steering Angle Sensor Module on Bus B Value of Signal Protection Calculation Incorrect
U1827 7FLost Communication with Steering Angle Sensor Module on Bus B Erratic
U1829 00Lost Communication with Gateway A on Bus B
U182A 00Lost Communication with Battery Energy Control Module on Bus B
U1842 00Electronic Brake Control Module Lost Communication with Engine Control Module on Bus B
U1843 00Electronic Brake Control Module Lost Communication with Hybrid Engine Control Module on Bus B
U1862 00Battery Energy Control Module Lost Communication with Communications Gateway Module
U1863 00Starter/Generator Control Module Lost Communication with Body Control Module
U1865 00Fuel Operated Heater Lost Communication with Engine Control Module
U1866 00Battery Energy Control Module Lost Communication with Body Control Module
U186A 00Lost Communication with Transfer Case Control Module
U186B 00Lost Communication with TCM
U1875 00Drive Motor A Control Module Lost Communication with Battery Energy Control Module
U1876 00Drive Motor A Control Module Lost Communication with Engine Control Module (ECM)/Powertrain Control Module (PCM)
U1878 00Drive Motor B Control Module Lost Communication with Battery Energy Control Module
U1879 00Drive Motor B Control Module Lost Communication with Engine Control Module (ECM)/Powertrain Control Module (PCM)
U1885 00Battery Energy Control Module Lost Communication with HP2 Powertrain Control Module
U1886 00Battery Energy Control Module Lost Communication with Engine Control Module (ECM)
U1888 00Hybrid Powertrain Control Module Lost Communication With Starter/Generator Control Module
U1897 00Starter/Generator Control Module Lost Communication with Battery Energy Control Module
U1899 00Starter/Generator Control Module Lost Communication with Engine Control Module/Powertrain Control Module
U189A 00DC to DC Converter Control Module A Lost Communication with HP2 Powertrain Control Module
U2099 00High Speed Communication Enable Circuit
U209A 00High Speed Communication Enable Circuit Low
U209D 00Battery Energy Control Module High Speed Communication Enable Circuit High
U2100 00Controller Area Network (CAN) Bus Communication
U2100 47Controller Area Network (CAN) Bus Communication
U2102 00More Controllers On Bus Than Programmed
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 ABS/TCS Control System
U2109 00Lost Communication with Powertrain Control Module
U2110 00Lost Communication with Chassis Multiple Control System
U2111 00Lost Communication with Steering Control Module
U2112 00Lost Communication with Electronic Suspension Control (ESC)
U2113 00Lost Communication with Sensing and Diagnostic Module (SDM)
U2114 00Lost Communication with PPS or CPS
U2115 00Lost Communication with Restraints Control System
U2116 00Lost Communication with Instrument Cluster
U2117 00Lost Communication with Info Display
U2118 00Lost Communication with Head Up Display (HUD)
U2119 00Lost Communication with Daytime Running Lamps Control Module
U2120 00Lost Communication with Automatic Headlamp Leveling Control Module
U2121 00Lost Communication with Radio Display
U2122 00Lost Communication with Radio
U2123 00Lost Communication with Compact Disc Changer (CDX)
U2124 00Lost Communication with Audio Amplifier
U2125 00Lost Communication with Telematic Unit
U2126 00Lost Communication with Mobile Communications Control System
U2127 00Lost Communication with Front HVAC Control Module
U2128 00Lost Communication with Rear HVAC Control Module
U2129 00Lost Communication with Remote Function Actuator (RFA)
U2130 00Lost Communication with Driver Door Module (DDM)
U2131 00Lost Communication with Driver Seat Module (DSM)
U2132 00Lost Communication with Passenger Door Module (PDM)
U2133 00Lost Communication with Passenger Seat Module (PSM)
U2134 00Lost Communication with Rear Door Module (RDM)
U2135 00Lost Communication with Rear Integration Module (RIM)
U2136 00Lost Communication with Memory Mirror Module (MMM)
U2137 00Lost Communication with Vehicle Theft Deterrent (VTD)
U2138 00Lost Communication with Column Locking Module (CLM)
U2139 00Lost Communication with Column Integration Module (CIM)
U2140 00Lost Communication with Underhood Electrical Center (UEC)
U2141 00Lost Communication with Rear Electrical Center
U2142 00Lost Communication with Yaw Rate Sensor (YRS)
U2143 00Lost Communication with Steering Angle Sensor (SAS)
U2144 00Lost Communication with Distance Sensing Cruise Control Module
U2145 00Lost Communication with Parking Assistance System (PAS)
U2146 00Lost Communication with Shift Lever Module (SLM)
U2147 00Lost Communication with Auxiliary Heater System (AHS)
U2148 00Lost Communication with Sun Roof Module (SRM)
U2149 00Lost Communication with Tire Pressure Monitor (TPM) System
U2150 00Navigation Electronic Control Unit (ECU) Gateway Communications
U2151 00Navigation Electronic Control Unit (ECU) Communications
U2152 00Navigation Bus Request Line Circuit Low
U2153 00Navigation Electronic Control Unit (ECU) - VICS Communication Circuit
U2160 00Lost Communication with Steering Control System Sensor
U2161 00Lost Communication with Dash Integration Module (DIM)
U2162 00Lost Communication with Instrument Panel integration Module (IPM)
U2163 00Lost Communication with Left Rear Door Module (LRDM)
U2164 00Lost Communication with Right Rear Door Module (RRDM)
U2165 00Lost Communication with Driver Door Switch (DDS)
U2166 00Lost Communication with Driver Position Module (DPM)
U2167 00Lost Communication with Remote Control Door Lock Receiver (RCDLR)
U2168 00Lost Communication with Side Object Detection (SOD) Module - Left
U2169 00Lost Communication with Side Object Detection (SOD) Module - Right
U2170 00Lost Communication with Four Wheel Drive (4WD) Clutch
U2171 00Lost Communication with Rear Seat Entertainment (RSE)
U2172 00Lost Communication with Digital Radio Receiver (DRR)
U2173 00Lost Communication with Passive Entry and Passive Start System
U2174 00Lost Communication with Parking Heater System
U2175 00Lost Communication with Special Vehicle Module
U2176 00Lost Communication with Power Take Off (PTO) Control Module
U2177 00Lost Communication with Cruise Control Module
U2178 00Lost Communication with Trailer Interface Module
U2179 00Lost Communication with Television Module
U2180 00Lost Communication with Folding Top Control Module
U2181 00Lost Communication with Moveable Roof Module

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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. No external circuits are 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 100, without a repeat of the malfunction.

Diagnostic Aids

  1. This DTC may be stored as a history DTC without affecting the operation of the control module.
  2. Do not replace a control module based only on DTC B1000 being set in history with the exception of the following control modules: Sensing and Diagnostic Module (SDM) Rollover Sensor Passenger Presence System Module
  3. If DTC B1000 is set as current, replace the appropriate control module.

Circuit/System Verification

If the DTC is set, replace the appropriate control module.

Repair Procedures

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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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.

Battery voltage is between 9-16 volts 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»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Verify DTC B1001 is not set. If the DTC is set, program the control module.
  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 DTC B1001 is not set. If the DTC is set, 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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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 control module microprocessor must be active/awake.

The KAM in the control module has been reset. It is a normal occurrence when battery positive voltage or ground is removed from the module, such as a battery disconnect.

The microprocessor reverts back to the base programmed critical operating data until new data is learned and stored in KAM.

  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»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify that DTC B1004 is not set.

  1. If the DTC is set, perform the setup procedure on the appropriate control module. If the DTC resets, replace the 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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The electrically erasable programmable read-only memory (EEPROM) check sum error detection is handled inside the control module.

The control module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground.

The control module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The control module then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the module sets the DTC.

The control module reverts to base operation values programmed for those blocks of data that have failed the check sum test.

  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, without a repeat of the malfunction.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. With a scan tool, clear the DTC. If the DTC will not clear, replace the module that set the DTC.
  2. Ignition OFF, remove the scan tool, open and close the drivers door.
  3. Wait 60 seconds, verify DTC B1009 is not set. If the DTC is set, replace the 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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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 C0550 is not set.

  1. If the DTC is set, replace the 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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) .

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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, DTC U0100-U02FF .

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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 are 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 module suspends all message transmission.
  2. The 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. The 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. 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. Refer to «Data Link References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-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 «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) or «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) .
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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
Module B+U0100-U02FFU0100-U02FF
Module IgnitionU0100-U02FFU0100-U02FF
Module GroundU0100-U02FFU0100-U02FF
Accessory Wake Up Serial DataU1814U0100-U02FF
High Speed GMLAN Serial Data Wake UpU2099U0100-U02FF
High Speed GMLAN Serial Data (+)2U0100-U02FF2
High Speed GMLAN Serial Data (-)2U0100-U02FF2
Low Speed GMLAN Serial Data1U0100-U02FF1
1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with 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 DLC, the scan tool can be used to monitor each 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 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 sets 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, for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note: a loss of serial data communications DTC does not represent a failure of the module that set it.

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. 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 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.
  4. Use «Data Link References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system__data-link-references) to determine if the module uses high or low speed GMLAN serial data communications.
  5. 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.
  6. 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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Verify that following BCM DTCs are not present

  1. U1814
  2. U2099
  3. B1428
  4. B1370
  5. B1380
  6. B1440
  7. B1441 If any listed DTC is present, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) to diagnose that DTC prior to this diagnostic.

Circuit/System Testing

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. Determine the module that is not communicating. Refer to «Control Module U Code List»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system__control-module-u-code-list) .
  2. Ignition OFF, disconnect the necessary harness connector of the module that is not communicating.
  3. Test for less than 5 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. 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 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 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.
  6. 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 circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  7. Ignition OFF for 60 seconds, test for less than 5 ohms between the serial data circuit terminals and the DLC terminal listed below: Class 2 serial data circuit terminal 2 Low speed GMLAN serial data terminal 1 High speed GMLAN serial data terminal 6 or 14 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.
  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»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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, «DTC U0100-U02FF»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) .
  2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the «DTC U0100-U02FF»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) procedure in order to isolate an intermittent condition.
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using the diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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 Data1U2105-U21991
Battery Positive Voltage CircuitsU2105-U2199U2105-U2199
Ignition Voltage CircuitsU2105-U2199U2105-U2199
Module Ground CircuitsU2105-U2199U2105-U2199
Accessory Wake Up Serial DataU1814U2105-U2199
High Speed GMLAN Serial Data Wake UpU2099U2105-U2199
1. Scan tool does not communicate with low speed GMLAN device

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 modules. The 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 volts.
  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 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 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 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 to determine if the 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. 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.
  1. «Data Communication Schematics»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

IMPORTANTIf more than one module is not communicating use Data Communication Schematics to determine which module is closest to the DLC. Start diagnostics with that module. Terminal and connector identifiers will be different depending on the individual module being tested. Use Schematic Reference and Connector End View Reference to determine which connector and terminal to access.
  1. Using the DTC Descriptor and Diagnostic Aids, determine the module that is not communicating that should be tested.
  2. Ignition OFF, disconnect the harness connector of the module that is not communicating.
  3. Test for less than 2 ohms between the module ground circuits and ground. If greater than specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the high speed GMLAN serial data wake up circuit OR the accessory wake up serial data circuit and ground. If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  5. Ignition ON, verify that a test lamp illuminates between all B+ circuits 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 positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the appropriate module.
  6. Verify that a test lamp illuminates between all ignition voltage circuits and ground. If the test lamp does not illuminate, test the ignition voltage circuits for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the appropriate module.
  7. Test for less than 1 ohm in the GMLAN serial data circuits between the non-communicating module and the module that displays the DTC. If greater than specified range, test the GMLAN serial data circuits for open/high resistance.
  8. If all circuits test normal, replace the module that is not communicating.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming

Symptoms - Data Communications

IMPORTANTThe following steps must be completed before using the symptom tables.
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/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: «Body Control System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system__body-control-system-description-and-operation) «Data Link Communications Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)
  2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)
  3. «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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 (PMM) 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/CANdi module.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#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/CANdi module user guide.

Perform the Diagnostic Repair Verification after completing the repair.

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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-U0299*1
High Speed GMLAN Serial Data (-)1U0100-U0299*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 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 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 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 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. When the scan tool attempts to communicate with the vehicle a message "no CANdi module detected" will be displayed.
  5. The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus.
  6. Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC) and no low speed GMLAN communications with the scan tool.
  7. 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. Tire Pressure Monitor (TPM) system warning lights.

Schematic Reference

  1. «Data Communication Schematics»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-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 6 Terminal 14 If greater than the specified range, test the serial data circuit for a short to voltage; refer to «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under 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 6 Terminal 14 If not the specified value, test the serial data circuit for a short to ground; refer to «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under 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 «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under 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 «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under 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 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 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 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 high 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 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 high 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 high 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 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 high 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 high 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 are 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 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»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/malibu/vii-2008-2012/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»(/chevrolet/malibu/vii-2008-2012/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. Note: 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'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 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 DLC ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle. When the scan tool attempts to communicate with the vehicle a No CANdi Module Detected message will be displayed.
  5. An open between the DLC and the BCM will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
  6. The engine will 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. Tire Pressure Monitor (TPM) system warning light.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#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 locations on the low speed serial data circuit Each control modules low speed serial data circuit terminals

  1. Attempt to communicate with all control modules on the low speed GMLAN serial data circuit, refer to «Data Link References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-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»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) . If one or more control modules are communicating but not all, refer to «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under 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 «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under 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 «Circuit/System Testing»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#data-communication-system) , under Testing the Serial Data Circuits for a Short to ground.
  6. Disconnect the appropriate harness connector at the BCM.
  7. Test for less than 2 ohms between the DLC serial data circuit terminal 1 and the BCM connector. If greater than the specified range, test the serial data circuit for an open/high resistance. If the circuits test normal, replace the BCM.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the appropriate harness connectors at the BCM.
  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 the BCM connectors and ground. If greater than the specified range, perform the appropriate test listed below
  1. 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.
  2. 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 BCM.
  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 and ground. If less than the specified range, perform the appropriate test listed below
  1. 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.
  2. 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. Ignition OFF, disconnect the appropriate harness connectors at the BCM.
  2. Install a 3 A fused jumper wire between the disconnected BCM connector DLC terminal and a low speed GMLAN serial data circuit terminal that is not communicating.
  3. 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 repair.

  1. «GMLAN Wiring Repairs»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/chevrolet/malibu/vii-2008-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming

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. 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 Module (BCM)High Speed GMLAN Low Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device and Scan Tool Does Not Communicate with Low Speed GMLAN Device
Digital Radio Receiver (DRR)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Disc Player Video DisplayLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Electronic Brake Control Module (EBCM)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Engine Control Module (ECM)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Generator Battery Disconnect Control Module (Hybrid only)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
HVAC Control Module (Auto only)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Inflatable Restraint Sensing and Diagnostic Module (SDM)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Instrument Panel Cluster (IPC)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Power Steering Control Module (PSCM)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
RadioLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Rear Seat Audio ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Remote Control Door Lock Receiver (RCDLR)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Starter Generator Control Module (SGCM)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Theft Deterrent Module (TDM)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Transmission Control Module (TCM)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Vehicle Communication Interface Module (VCIM)High Speed GMLAN - pass through only Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device

Scheme 8

Scheme 8: Body Control Module Replacement
Scheme 8: Body Control Module Replacement
CalloutComponent Name
Preliminary Procedure: Remove the front floor console extension panel - right side. Refer to Front Floor Console Extension Panel Replacement - Right Side .
1Body Control Module Bolt Screw (Qty: 3) CAUTION: Refer to Fastener Caution . Tighten: 1.5 N.m (13 lb in)
2Body Control Module Procedure If the scan tool can communicate with the BCM that is being replaced, select BCM copy and flash to copy information from that BCM before removal. Disconnect the electrical connections. Refer to Control Module References for programming and set up procedures.
CAUTION
Refer to Fastener Caution .

Body Control System Description and Operation

This vehicle's body control module (BCM) has a bussed electrical center integrated into the housing. Body control relays and fuses are installed directly on the BCM, which simplifies wiring and junction blocks on the vehicle. The body control system consists of the BCM and its associated controls. Battery positive voltage is provided to the BCM from IBCM BATT 1 fuse and the IBCM BATT 2 fuse in the underhood fuse block. The module grounds are wired to ground G201, G203 and G305. The BCM is wired to the GMLAN High speed serial data buss, and the GMLAN Low speed serial data buss, as well as discrete input and output terminals to control the functions of the vehicle's body.

Power Mode Master

This vehicles body control module (BCM) functions as the power mode master (PMM). Refer to Power Mode Description and Operation for a complete description of power mode functions.

Serial Data Gateway

The body control module (BCM) in this vehicle functions as a translator between the High and Low speed GMLAN busses. The 2 communication protocols use the BCM to translate communicated serial data messages between the control modules over the 2 serial data busses.

Body Control Module

The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. The BCM functions include the following

  1. A/C compressor request-Refer to «Air Temperature Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation) .
  2. A/C cooling fan-Refer to «Air Delivery Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/manual-hvac-system/#hvac-system-manual__air-delivery-description-and-operation) .
  3. Battery rundown protection (inadvertent power)-Refer to «Interior Lighting Systems Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/exterior-lights/#lighting-system) .
  4. Bulb check-Refer to «Instrument Cluster Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges) .
  5. Chimes-Refer to «Indicator/Warning Message Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges__indicatorwarning-message-description-and-operation) . Check gauges Door ajar warning Headlamps ON Key-in-ignition Oil reset Park brake warning Seat belt not fastened Turn signal ON
  6. Door lock interface-Refer to «Power Door Locks Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/door-locks-anti-theft-systems/#door-lock-systems-door-handles) .
  7. Electronic power steering (EPS)-Refer to «Power Steering System Description and Operation (Hydraulic Power Steering)»(/chevrolet/malibu/vii-2008-2012/remont/electronic-steering/#power-steering-system) or «Power Steering System Description and Operation (EPS)»(/chevrolet/malibu/vii-2008-2012/remont/electronic-steering/#power-steering-system) .
  8. Engine coolant level sensing-Refer to «Cooling System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-description-and-operation) .
  9. Exterior and interior lighting control-Refer to «Exterior Lighting Systems Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/exterior-lights/#lighting-system) . Automatic lighting control Daytime running lamps (DRL) Fog lamps Park brake lights Turn hazard lamps
  10. Gauge control-Refer to «Instrument Cluster Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges) .
  11. Horn interface-Refer to «Horns System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/horns/#horn-system) .
  12. Instrument cluster indicator control-Refer to «Instrument Cluster Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges) .
  13. Interior lighting-Refer to «Interior Lighting Systems Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/exterior-lights/#lighting-system) .
  14. Key-in-ignition sensing-Refer to «Indicator/Warning Message Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges__indicatorwarning-message-description-and-operation) .
  15. Parking brake state sensing-Refer to «Brake Warning System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/mechanical-hydraulic/#hydraulic-brake-system) .
  16. Retained accessory power (RAP)-Refer to «Retained Accessory Power Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/body-electrical/#wiring-systems-and-power-management-description-and-operation) .
  17. Rear compartment interface-Refer to «Power Door Locks Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/door-locks-anti-theft-systems/#door-lock-systems-door-handles) .
  18. Rear defogger-Refer to «Rear Window Defogger Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/heated-glassdefoggers/#fixed-and-moveable-windows-system) .
  19. Remote function control-Refer to «Keyless Entry System Description and Operation (without Accessory 2 Way Remote)»(/chevrolet/malibu/vii-2008-2012/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-operation) or «Keyless Entry System Description and Operation (with Accessory 2 Way Remote)»(/chevrolet/malibu/vii-2008-2012/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-operation) .
  20. Seat belt use sensing-Refer to «Seat Belt System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/restraints-control-systems/#seat-belt-system) .
  21. Content theft deterrent-Refer to «Content Theft Deterrent (CTD) Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/door-locks-anti-theft-systems/#theft-deterrent-system__content-theft-deterrent-ctd-description-and) .
  22. Washer solvent level sensing-Refer to «Wiper/Washer System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/wiperwasher-systems/#wiper-system-washer-system) .
  23. Wiper/washer-Refer to «Wiper/Washer System Description and Operation»(/chevrolet/malibu/vii-2008-2012/remont/wiperwasher-systems/#wiper-system-washer-system) .

The communication among control modules is performed through the GMLAN high speed serial data circuit and the GMLAN low speed serial data circuit. The modules that need real time communication are attached to the high speed GMLAN network. The body control module (BCM) is the gateway between the networks. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss. The gateway will interact with each network according to that network's transmission protocol. Refer to Body Control System Description and Operation for more information about the gateway.

GMLAN High Speed Circuit Description

IMPORTANTA loss of serial data DTC does not represent a failure of the module that the code is set in.

The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data circuit. The serial data is transmitted on two twisted wires that allow speed up to 500 Kb/s. The twisted pair is terminated with two 120 ohms resistors, one is internal to the powertrain control module (PCM) or engine control module (ECM) depending on regular production option (RPO) and the other is internal to the body control module (BCM). The BCM is considered the DLC termination point of the link and the engine management controller is the other end of the link. The resistors are used to reduce noise on 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. The idle level, which is approximately 2.5 volts, is considered recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes, adds one volt to the high speed GMLAN serial data bus (+) and subtracts one volt from the high speed GMLAN serial data bus (-) wire. This dominant state is interpreted as a logic 0. GMLAN network management supports selective start up and is based on virtual networks. A virtual network is a collection of signals started in response to a vehicle event. The starting of a virtual network signifies that a particular aspect of the vehicles functionality has been requested. A virtual network is supported by virtual devices, which represents a collection of signals owned by a single physical device. So, any physical device can have one or more virtual devices. The signal supervision is the process of determining whether an expected signal is being received or not. Failsofting is the ability to substitute a signal with a default value or a default algorithm, in the absence of a valid signal. Some messages are also interpreted as a heartbeat of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual device. This code is mapped on the Tech 2 screen as a code against the physical device.

GMLAN Low Speed Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the low speed GMLAN serial data circuit. 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. This protocol produces a simple pules train sent out over the GMLAN low speed serial data bus. When a module pulls the buss high, 5 volts, this creates a dominant logic state or 0 on the buss. When the buss is pulled low 0 volts, it is translated as a recessive logic state or 1. To wake the control modules connected to the GMLAN low speed serial data buss, a high voltage wake up pulse is sent out over the buss, the voltage level of the pulse is +10 volts. Modules connected to the GMLAN low speed buss can be part of a virtual network as described in the previous paragraph. The modules on the GMLAN low speed serial data buss are connected to the buss in a parallel configuration.

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 GMLAN low speed communications terminal
  2. Pin 4 Scan tool power ground terminal
  3. Pin 5 Common signal ground terminal
  4. Pin 6 High speed GMLAN serial data bus (+) terminal
  5. Pin 14 High speed GMLAN serial data bus (-) terminal
  6. Pin 16 Scan tool power, battery positive voltage terminal

Serial Data Reference

The scan tool communicates over the various busses on the vehicle. When a scan tool is installed on a vehicle, the scan tool will try to communicate with every 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 options control module. In order to avert misdiagnoses of No Communication with a specific module, refer to Data Link References for a list of modules, the busses they communicate with, and the RPO codes for a specific module.

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Diagnostic Repair Verification
• Control Module References
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Diagnostic Trouble Code (DTC) List - Vehicle
• Checking Aftermarket Accessories
• Front Floor Console Extension Panel Replacement - Right Side
• Fastener Caution
• Power Mode Description and Operation
• Air Temperature Description and Operation
• Air Delivery Description and Operation
• Interior Lighting Systems Description and Operation
• Instrument Cluster Description and Operation
• Indicator/Warning Message Description and Operation
• Power Door Locks Description and Operation
• Power Steering System Description and Operation (Hydraulic Power Steering)
• Cooling System Description and Operation
• Horns System Description and Operation
• Brake Warning System Description and Operation
• Retained Accessory Power Description and Operation
• Rear Window Defogger Description and Operation
• Keyless Entry System Description and Operation (without Accessory 2 Way Remote)
• Seat Belt System Description and Operation
• Content Theft Deterrent (CTD) Description and Operation
• Wiper/Washer System Description and Operation
• DTC B1000
• Data Link References
• Control Module U Code List
• Body Control System Description and Operation

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