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Data Communication System Cadillac CTS II

Communication Devices 9 illustrations ~12759 words

Scheme 3

Scheme 3: Data Communication Schematics
Scheme 3: Data Communication Schematics

Scheme 4

Scheme 4
Scheme 4

Scheme 5

Scheme 5
Scheme 5

Scheme 6

Scheme 6: Body Control System Schematics
Scheme 6: Body Control System Schematics

Scheme 7

Scheme 7
Scheme 7

Scheme 8

Scheme 8
Scheme 8

Scheme 9

Scheme 9
Scheme 9

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 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 B1009B1009: EEPROM Checksum Mismatch/Error
DTC B101DB101D XX: ECU Hardware
DTC B101EB101E XX: ECU Software
DTC C0550C0550 00: Electronic Control Unit (ECU) Performance C0550 31: Electronic Control Unit (ECU) Performance C0550 32: ECU Performance General Memory Failure C0550 34: ECU Malfunction RAM Failure C0550 35: ECU Malfunction ROM Failure C0550 36: ECU Malfunction EEPROM Failure C0550 37: ECU Malfunction Watch Dog failure C0550 38: ECU Performance Supervision Software Failure C0550 39: ECU Performance Internal Electronic Failure/Discard C0550 4B: ECU Internal Fault
DTC C056DC056D XX: Electronic Control Unit Hardware
DTC C056EC056E XX: Electronic Control Unit Software
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-U0299Supervised Periodic Message Not Received
DTC U0400-U05FFControl Module Is Not Configured Properly
DTC U1500, U1511, U1512, or U1513U1500 01: Inter-Device Dedicated Bus 1 Short to Battery U1500 02: Inter-Device Dedicated Bus 1 Short to Ground U1511 00: Inter-device Dedicated Bus Lost Communication With Device 1 U1512 00: Inter-device Dedicated Bus Lost Communication With Device 2
DTC U1814U1814 00: Powertrain High Speed Communication Enable Circuit
DTC U1826 or U1827U1826 71: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Invalid Serial Data Received U1826 72: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Alive Counter Incorrect/Not Updated U1826 7F: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Erratic U1827 71: Lost Communication With Steering Angle Sensor Module on Bus "B" Invalid Serial Data U1827 72: Lost Communication With Steering Angle Sensor Module on Bus "B" Alive Counter Incorrect/Not Updated U1827 74: Lost Communication With Steering Angle Sensor Module on Bus "B" Value of Signal Protection Calculation Incorrect U1827 7F: Lost Communication With Steering Angle Sensor Module on Bus "B" Erratic
DTC U2099U2099 00: High Speed Communication Enable Circuit

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
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
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
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
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
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
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
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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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.
  1. Program or configure the module or related module that set DTC B1001. The module should successfully configure. If the module will not configure, replace the module that set the DTC.
  2. With a scan tool, clear the DTC.
  3. Ignition OFF, remove the scan tool, open and close the drivers door.
  4. Wait 60 seconds, then recheck for DTCs. DTC B1001 should not set. If DTC B1001 sets, 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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. 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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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 control module.
  2. Do not replace a control module based only on DTC B101D being set in history with the exception of the following control modules: Sensing and Diagnostic Module (SDM) Passenger Presence System Module
  3. If DTC B101D is set as current, replace the appropriate control module.

Verify that DTC B101D is not set.

  1. If the DTC is set, 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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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

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

The control module is not configured properly.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify DTC B101E is not set.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

When the ignition is turned ON, the microprocessor runs a diagnostic program to detect an internal fault when power up is commanded. If an internal malfunction is detected, the control module will store a DTC C0550 in its memory.

The microprocessor runs a diagnostic program to detect an internal fault when power up is commanded. The only requirements are voltage and ground.

  1. The control module detects an internal write malfunction.
  2. The control module detects an internal checksum malfunction.
  1. The affected system warning indicator/warning message will activate.
  2. The affected system will be disabled.
  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.
  1. With a scan tool, clear DTC C0550. The DTC should clear. If the DTC will not clear, replace the control module.
  2. Ignition OFF, remove the scan tool, open and close the drivers door.
  3. Wait 60 seconds, ignition ON, then recheck for DTCs. DTC C0550 should not set. If DTC C0550 sets, 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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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

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

The module has detected an internal malfunction.

The module refuses all additional inputs.

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

Verify that DTC C056D is not set.

  1. If the DTC is set, 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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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

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

The control module is not configured properly.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

Verify DTC C056E is not set.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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-U0299 .

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) or «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) .
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptor

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U0100-U0299U0100-U0299
Module IgnitionU0100-U0299U0100-U0299
Module GroundU0100-U0299U0100-U0299
Accessory Wake Up Serial DataU1814U0100-U0299
High Speed GMLAN Serial Data Wake UpU2099U0100-U0299
High Speed GMLAN Serial Data (+)2U0100-U02992
High Speed GMLAN Serial Data (-)2U0100-U02992
Low Speed GMLAN Serial Data1U0100-U02991
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 data link connector (DLC), the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the control module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.

The system voltage is between 9-16 V.

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

  1. Specific subsystems will not function.
  2. DTC U0100 in the TCM will cause the transmission to go into default gears.
  3. Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
  1. The ECM/TCM module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
  2. A current DTC clears when the malfunction is no longer present.
  3. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
  5. Use «Data Link References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system__data-link-references) to determine if the control module uses high or low speed GMLAN serial data communications.
  6. Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.
  7. 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»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Determine the control module that is not communicating. Refer to «Control Module U Code List»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system__control-module-u-code-list) .
  2. Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
  3. Engine running for 10 seconds.
  4. Ignition ON, engine OFF, verify that DTC U0100-U0299 is not set with symptom byte 00. If the DTC U0100-U0299 is set with symptom byte 00, refer to «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system__circuitsystem-testing) .
  5. Verify that DTC U0100-U0299 is not set with symptom byte 71 or 72. If the DTC U0100-U0299 is set with symptom byte 71 or 72 along with other DTCs set, diagnose all other codes first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If the DTC U0100-U0299 is set with symptom byte 71 or 72 and without other DTCs set, reprogram the control module. If the DTC resets, replace the control module.

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. Ignition OFF, disconnect the harness connector at of the control module that is not communicating.
  2. Test for less than 10 ohms between each ground circuit terminal and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground. If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the BCM, for an open/high resistance or short to ground. If the circuits test normal, replace the BCM.
  6. Ignition OFF for 60 seconds, test for less than 5 ohms between the serial data circuit terminals and the appropriate 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.
  7. 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»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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

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

The control module is not configured properly.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

  1. Engine running for 10 seconds.
  2. Ignition ON, engine OFF, verify the DTC U0400-U05FF is not set. If the DTC U0400-U05FF is set along with other DTCs set, diagnose all other codes first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If the DTC U0400-U05FF is set without other DTCs set, program the control module specified by the DTC descriptor. If the DTC resets, replace the appropriate control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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 Voltage
B+ - Window MotorU1511, U1512U1511, U1512
Ignition - Electronic Compass ModuleU1511U1511
Serial Data - Electronic Compass Module, Terminal 3U1511U1511U1511
Serial Data- Driver Window Motor, Terminal 5U1500 02U1511U1500 01
Serial Data - Passenger Window Motor, Terminal 5U1500 02U1512U1500 01
Ground - Electronic Compass ModuleU1511
Ground - Window MotorU1511 1 , U1512 1
1 Either or both DTC may set depending on the location of the open/high resistance.

The driver door module (DDM) and the front passenger door module (FPDM) communicate with window regulator motors on the local interconnect network bus 1 and the local interconnect network bus 2 circuits respectively. When the driver power window switch is activated to a desired position, the DDM examines the request and checks for messages from other vehicle control modules prohibiting window movement. If no prohibitive messages have been received, the DDM will send a LIN serial data message to the driver door window motor to move the window to the desired position.

When the DDM receives a request to operate one of the right side passenger windows from the driver master control, a GMLAN serial data message is sent to the PDM. The PDM examines the request and checks for messages from other vehicle control modules prohibiting the window movement. If no prohibitive messages have been received, the PDM will send a LIN serial data message to the appropriate window motor to move the window as requested.

The DDM and PDM supply their respective rear power window switches with a 12-volt reference and signal circuit. The rear power window switches contain separate resistors for each switch position. When a rear power window switch is activated, the associated door control module interprets the signal and checks for messages from other vehicle control modules prohibiting the window movement. If no prohibitive messages have been received, the door control module sends a LIN serial data message to the appropriate power window motor commanding the requested window position.

The driver information center (DIC) displays the compass based on serial data message from the BCM. The compass module communicates with the body control module (BCM) through a bi-directional data circuit (LIN). The instrument panel cluster (IPC) receives compass information from the BCM via the serial data circuit.

The system voltage is between 9-16 volts.

U1500 01

When there is a short to voltage in the local interconnect network bus circuit.

U1500 02

When there is a short to ground in the local interconnect network bus circuit.

U1511, U1512

The DTC will set when there is an open/high resistance in the local interconnect network bus circuit, or an open in the voltage or ground circuits of the motor or module.

U1500

The individual LIN bus will be inoperative, disabling all windows on one side of the vehicle.

U1511

  1. If set in the driver door lock window switch or passenger door lock window switch, no window on the specific side of the vehicle will operate if the open is before the first splice from the door module, and both DTC U1511 and U1512 should set. If open after the first splice, the individual window will be inoperative and a single DTC should set.
  2. If set in the BCM, the compass is inoperative in the DIC.

U1512

No window on the specific side of the vehicle will operate if the open is before the first splice from the door module, and both DTC U1511 and U1512 should set. If open after the first splice, the individual window will be inoperative and a single DTC should set.

  1. The current DTC will clear 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. A window regulator motor may cause a short to the local interconnect network bus circuit, and will cause all windows on one side to be inoperative.
  2. An open/high resistance between the door module and the first splice from the module will cause all windows on one side to be inoperative.
  3. An open/high resistance between the window regulator motor and the first splice from the motor will cause only one window to be inoperative.
  4. Use the DMM MIN/MAX function to capture/locate intermittent conditions.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for Scan Tool Information

  1. With a scan tool, verify that DTC U1511 is not set in the BCM. If DTC U1511 is set in the BCM, perform the Compass Malfunction Test.
  2. Perform the Window Malfunction Test

Compass Malfunction Test

  1. Ignition OFF, disconnect the harness connector at the electronic compass module.
  2. Ignition OFF, test for less than 5.0 ohm between the ground circuit terminal 2 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the ignition voltage circuit terminal 1 and ground. If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance.
  4. Test for 6.0-7.0 volts between the LIN circuit terminal 3 and ground. If greater than the specified range, test the LIN circuit for a short to voltage. If the circuit tests normal, replace the BCM. If less than the specified range, test the LIN circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, replace the electronic compass module.

Window Malfunction Test

  1. Ignition OFF, disconnect the harness connector at the appropriate window motor.
  2. Ignition OFF, test for less than 2.0 ohm between the ground circuit terminal 4 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 3 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Test for 6.0-7.0 volts between the LIN circuit terminal 5 and ground. If greater than the specified range, test the LIN circuit for a short to voltage. If the circuit tests normal, replace the applicable door module. If less than the specified range, test the LIN circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable door module.
  5. Ignition OFF, reconnect the harness connector at the window motor.
  6. Ignition ON, observe the appropriate scan tool Window Motor Fault Status parameter while raising and lower the window. The parameter should read No Fault. If the parameter displays Not Normalized, refer to «Window Regulator Motor Programming and Setup»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems) . If the parameter reads Motor Fault, Hall Fault, Memory Fault, LIN Fault, Anti-Trap Fault or Thermo Active, test or replace the appropriate power window motor.
  7. If all circuits test normal, replace the appropriate door module.
IMPORTANTEach window regulator motor or front window and door lock switch, if replaced needs to be setup for proper operation.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for window, and door lock switch (door module) or window regulator motor replacement, setup, and programming
  2. «Electronic Compass Module Replacement (Sedan)»(/cadillac/cts/ii-2007-2014/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges) or «Electronic Compass Module Replacement (Wagon)»(/cadillac/cts/ii-2007-2014/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges)
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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
Accessory Wake Up Signal Serial DataU1814U0100

The accessory wake up serial data circuit is a voltage wake up signal from the body control module (BCM) to the engine control module (ECM) and the transmission control module (TCM). The signal is activated in 2 ways; any time the ignition switch is in the ACC or RUN position, or anytime the BCM determines that communication is needed from the powertrain. When the ignition switch is in the ACC or RUN position, the accessory voltage circuit input to the BCM is internally connected to the accessory wake up serial data circuit output, and voltage is supplied to the modules. The BCM also supplies voltage to the accessory wake up serial data circuit when it determines that communication is necessary with the powertrain and the ignition is not in the ACC or RUN position such as during remote start.

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

The BCM senses a short to ground on the accessory wake up serial data circuit.

  1. The modules use a default value for the missing parameters until the next ignition cycle.
  2. The modules is never signaled, therefore the specific subsystems will not function.
  3. The vehicle may not start.
  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. Short to ground may open the fuse feeding the ignition switch.
  2. Short to ground may also set multiple no communication DTCs for GMLAN high speed modules.

Schematic Reference

  1. «Body Control System Schematics»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  2. «Data Communication Schematics»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the X1 harness connector at the ECM and the TCM one at a time. After each disconnect, test for current DTCs. DTC U1814 should remain current. If the DTC becomes history, replace the module disconnected when the DTC became history.
  2. Ignition OFF, disconnect the X4 harness connector at the BCM.
  3. Test for infinite resistance between the signal circuit terminal 19 and ground. If less than the specified value, test the signal circuit for a short to ground.
  4. If all circuits tests normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming
  2. «GMLAN Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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
Steering Wheel Position Sensor Can Bus High Serial DataU1827 7FU1827 7FU1827 7FU1827 7F
Steering Wheel Position Sensor Can Bus Low Serial DataU1827 7F1827 7FU1827 7FU1827 7F
Vehicle Yaw Sensor Can Bus High Serial DataU1826 7FU1826 7FU1826 7FU1826 7F
Vehicle Yaw Sensor Can Bus Low Serial DataU1826 7FU1826 7FU1826 7FU1826 7F
Vehicle Yaw Sensor Low ReferenceU1826 7FU1826 7FU1826 7FU1826 7F
Steering Wheel Position Sensor Low ReferenceU1827 7FU1827 7FU1827 7FU1827 7F
Vehicle Yaw Sensor 12-volt ReferenceU1826 7FU1826 7FU1826 7FU1826 7F
Steering Wheel Position Sensor 12-volt ReferenceU1827 7FU1827 7FU1827 7FU1827 7F
Defective Yaw/Lat Sensor U1826 71, U1826 72 Defective Steering Angle Sensor U1827 71, U1827 72, U1826 74

The electronic brake control module (EBCM) activates the other modules connected to the CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Yaw Rate Sensor, and the Steering Angle or Steering Wheel Position Sensor are the only modules connected to the CAN bus serial data circuits. For more information on CAN bus serial data refer to Data Link Communications Description and Operation .

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

A supervised periodic message that includes the transmitter module availability is missing or invalid.

  1. The EBCM disables the VSES for the duration of the ignition cycle.
  2. The driver information center (DIC) displays the STABILITRAK Off message.
  3. The ABS/TCS remains functional.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Use the DTC Descriptor list above to determine the module which is not communicating.
  2. If there are multiple non-communicating modules choose the one closest to the EBCM.

Schematic Reference

  1. «Data Communication Schematics»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  2. «Antilock Brake System Schematics»(/cadillac/cts/ii-2007-2014/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system)
  3. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Yaw Rate Sensor DTC U1826

  1. Use the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
  2. Ignition OFF, disconnect the harness connector at the Yaw Rate Sensor.
  3. Ignition ON, verify that a test lamp illuminates between the Yaw Rate Sensor voltage (12-volt ref) circuit terminal 1 and ground. If the test lamp does not illuminate, test the circuit for a short to ground, or open/high resistance. If the circuit tests normal, replace the EBCM.
  4. Ignition OFF, test for less than 5 ohms between the Yaw Rate Sensor low reference circuit terminal 6 and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
  5. Test for less than 1 ohm in the CAN bus serial data circuits between the Yaw Rate Sensor terminals 3 and 2, and the EBCM connector 21 and 33. If greater than 1 ohm, test the serial data circuits for open/high resistance.
  6. If all circuits test normal, replace the yaw rate sensor.

Steering Wheel Position Sensor (Steering Angle Sensor) DTC U1827

  1. Use the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
  2. Ignition OFF, disconnect the harness connector at the Steering Wheel Position Sensor.
  3. Ignition ON, verify that a test lamp illuminates between the Steering Wheel Position Sensor voltage (12-volt ref) circuit terminal 5 and ground. If the test lamp does not illuminate, test the circuit for a short to ground, or open/high resistance. If the circuit tests normal, replace the Steering Wheel Position Sensor.
  4. Ignition OFF, test for less than 5 ohms between the Steering Wheel Position Sensor low reference circuit terminal 6 and ground. If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the Steering Wheel Position Sensor.
  5. Test for less than 1 ohm in the CAN bus serial data circuits between the Steering Wheel Position Sensor terminal 2 and 3, and the Yaw Rate Sensor terminal 5 and 4. If greater than 1 ohm, test the serial data circuits for open/high resistance.
  6. If all circuits test normal, replace the Steering Wheel Position Sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «GMLAN Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement»(/cadillac/cts/ii-2007-2014/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system)
  3. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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 Wake UpU2099, U0100-U0299*U0100-U0299U0100-U0299**
* Vehicle will not start. ** May be history only. If cleared the DTC should return after several ignition cycles.

The body control module (BCM) applies voltage to the high speed GMLAN serial data wake up circuit, when the ignition key is in ACC, ON or START to enable several modules for bus communication.

Depending on option content, modules that may receive the signal are as follows

  1. Electronic brake control module (EBCM)
  2. Electronic suspension control (ESC) module - (FE1) (F55)
  1. The system voltage is between 9-16 volts.
  2. The BCM attempts to enable the modules connected to the high speed GMLAN serial data wake up circuit.

The BCM senses a short to ground on the high speed GMLAN serial data wake up circuit.

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

Schematic Reference

  1. «Body Control System Schematics»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  2. «Data Communication Schematics»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)
  1. With the ignition OFF, disconnect the harness connector at the EBCM and ESC module one at a time. After each disconnect, clear the DTC, cycle the ignition key 3 times, then retest for the DTC. DTC U2099 should reset. If the DTC does not reset, replace the last module disconnected.
  2. Ignition OFF, disconnect the harness connector X3 of the BCM.
  3. With all modules disconnected, test for infinite resistance between the high speed GMLAN serial data wake up circuit and ground. If less than specified, repair the wake up circuit for a short to ground.
  4. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system__body-control-system-description-and-operation) «Data Link Communications Description and Operation»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__checking-aftermarket-accessories) .
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

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

Symptom List

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

  1. «Scan Tool Does Not Power Up»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  3. «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information.

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

Perform the Diagnostic Repair Verification after completing the repair.

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

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

  1. Attempt to communicate with all control modules on the high speed GMLAN serial data circuit, refer to «Data Link References»(/cadillac/cts/ii-2007-2014/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-U0299»(/cadillac/cts/ii-2007-2014/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 Testing the Serial Data Circuits for a Short to Voltage in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) .
  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 Testing the Serial Data Circuits for a Short to ground in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) .
  6. Test for 50-70 ohms between the serial data circuits terminal 6 and terminal 14. If less than 35 ohms, test for a short between the serial data circuits; refer to Testing the Serial Data Circuits for a Short between the Circuits in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) . If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance; refer to Testing the Serial Data Circuits for an Open/High Resistance in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) . 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»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/cts/ii-2007-2014/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»(/cadillac/cts/ii-2007-2014/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 Data (+)12*1
Ground (DLC, terminal 5)1*
* An open between the data link connector (DLC) and JX 201, or DLC terminal 5 ground will only effect the communication with the scan tool. See Diagnostic Aids. 1. No communication on any low speed GMLAN module 2. No communication on a specific low speed GMLAN module, or group of modules

Modules connected to the low speed GMLAN serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The low speed GMLAN serial data circuit uses JX 201 and JX 301 as common connection points between some modules and the data link connector (DLC).

  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 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 low speed GMLAN serial data circuit between the splice pack and a module will only affect that specific module. This type of failure will set a loss of communication DTC for each module effected, and the other modules will still communicate.
  5. An open in the 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.
  6. An open between the DLC and JX 201 will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
  7. The engine will not start when there is a total malfunction of the low speed GMLAN serial data circuit.
  8. Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC) and no low speed GMLAN communications with the scan tool. These conditions may be caused by the installation of an aftermarket navigation radio module (see bulletins). Some customers may comment of one or more of the following concerns: Vehicle will not crank. Vehicle cranks but will not start. Vehicle stability enhancement system warning lights and messages. PRNDL gear indicator position errors. Tire Pressure Monitor (TPM) system warning lights.

Schematic Reference

Connector End View Reference

  1. «Component Connector End Views»(/cadillac/cts/ii-2007-2014/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
  2. «Splice Pack Connector End Views»(/cadillac/cts/ii-2007-2014/remont/body-electrical/#wiring-systems-and-power-management-splice-pack-connector-end-views)

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Note. Use the schematic to identify the following: Control modules the vehicle is equipped with Control module locations on the low speed GMLAN serial data circuit Each control module's low speed GMLAN 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»(/cadillac/cts/ii-2007-2014/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-U0299»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) . If one or more control modules are communicating but not all, refer to Testing the Serial Data Circuit for an Open/High Resistance in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/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 circuit terminal 1 and ground. If greater than the specified range, test the serial data circuit for a short to voltage, refer to Testing the Serial Data Circuit for a Short to Voltage in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) .
  5. Ignition OFF for 60 seconds, test for greater than 100 ohms between the serial data circuit terminal 1 and ground. If not the specified value, test the serial data circuit for a short to ground, refer to Testing the Serial Data Circuits for a Short to ground in «Circuit/System Testing»(/cadillac/cts/ii-2007-2014/remont/communication-devices/#data-communication-system) .
  6. Disconnect the harness connector at the JX 201 splice pack.
  7. Test for less than 2 ohms between the serial data circuit terminal 1 and the JX 201 splice pack terminal 1. If greater than the specified range, test the serial data circuit for an open/high resistance. If the circuits test normal, replace the splice pack.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors at the JX 201 and JX 301 splice packs, as equipped.
  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 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 harness connectors at the JX 201 and JX 301 splice packs, as equipped.
  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. If equipped with a JX 301 splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the JX 301 splice pack. If all control modules on the JX 301 splice pack do not communicate, test the serial data circuit between the JX 201 and JX 301 splice packs for an open/high resistance. If the circuit tests normal, test each splice pack for an open/high resistance.
  2. Ignition OFF, disconnect one of the harness connectors listed below: JX 201 if the control modules not communicating are connected to the JX 201 splice pack JX 301 if the control modules not communicating are connected to the JX 301 splice pack, if equipped
  3. Install a 3A fused jumper wire between the disconnected splice pack terminal 1 and a low speed GMLAN serial data circuit that is not communicating.
  4. 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»(/cadillac/cts/ii-2007-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  2. «Control Module References»(/cadillac/cts/ii-2007-2014/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
Audio AmplifierLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Automatic Forward Lighting System (AFS) ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Auxiliary Body Control Module (XBCM)High Speed GMLAN Low Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Body Control Module (BCM)High Speed GMLAN Low Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Driver Door Module (DDM)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Driver Position (Memory Seat) ModuleLow 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
Electronic Compass ModuleLocal Interconnect Network (LIN)DTC U1500, U1511, U1512, or U1513
Electronic Park Brake Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Electronic Suspension Control (ESC) ModuleHigh 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
Fuel System Control Module (FSCM)High Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
HVAC Control ModuleLow 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
Inflatable Restraint Passenger Presence System (PPS)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
Passenger Door Module (PDM)Low Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Pedestrian Impact Detection System (PIDS) ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
RadioLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Radio HVAC Control ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Rear Park Assist (RPA) ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Remote Control Door Lock ReceiverLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Theft Deterrent AlarmLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Theft Deterrent Control ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Transfer Case Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
Transmission Control ModuleHigh Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device
TV Antenna ModuleLow Speed GMLANScan Tool Does Not Communicate with Low Speed GMLAN Device
Vehicle Control Interface Module (VCIM)High Speed GMLAN Low Speed GMLANScan Tool Does Not Communicate with High Speed GMLAN Device

Scheme 10

Scheme 10: Auxiliary Body Control Module Replacement (UA2)
Scheme 10: Auxiliary Body Control Module Replacement (UA2)
CalloutComponent Name
Preliminary Procedure: Remove the rear compartment side trim panel. Refer to Rear Compartment Side Trim Panel Replacement .
1Auxiliary Body Control Module Procedure Disconnect the electrical connectors. Refer to Control Module References for programming and set-up information.

Scheme 11

Scheme 11: Body Control Module Replacement
Scheme 11: Body Control Module Replacement
CalloutComponent Name
Preliminary Procedures Remove the instrument panel (I/P) insulator. Refer to Instrument Panel Insulator Replacement - Left Side (Left Hand Drive) or Instrument Panel Insulator Replacement - Left Side (Right Hand Drive) . Remove the driver knee bolster bracket. Refer to Driver Knee Bolster Bracket Replacement (Left Hand Drive) or Driver Knee Bolster Bracket Replacement (Right Hand Drive) .
1Body Control Module (BCM) Procedure Disconnect the electrical connectors. Refer to Control Module References for programming and set-up information.

Body Control System Description and Operation

The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the BCM. The BCM also has discrete input and output terminals to control the vehicle's body functions. Battery positive voltage is provided to the BCM from the BCM fuse in the underhood fuse block. The module has two grounds at G 202 as well as one directly to the vehicle battery. The BCM is wired to the GMLAN High speed serial data buss and the GMLAN Low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine/powertrain control module (ECM/PCM) and vehicle theft deterrent (VTD) control module to communicate without the BCM providing the gateway function.

Power Mode Master

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

Gateway

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

One example of this necessary communication is the communication between the engine/powertrain control module (ECM/PCM) which is high speed serial data and vehicle theft deterrent (VTD) control module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.

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

Body Control

The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. The BCM related systems include, but are not limited to the following

  1. Chimes-Refer to «Audible Warnings Description and Operation»(/cadillac/cts/ii-2007-2014/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges__audible-warnings-description-and-operation) .
  2. Exterior lighting-Refer to «Exterior Lighting Systems Description and Operation»(/cadillac/cts/ii-2007-2014/remont/exterior-lights/#lighting-system) .
  3. Instrument cluster indicator control-Refer to «Instrument Cluster Description and Operation»(/cadillac/cts/ii-2007-2014/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges) .
  4. Interior lighting-Refer to «Interior Lighting Systems Description and Operation»(/cadillac/cts/ii-2007-2014/remont/exterior-lights/#lighting-system) .
  5. Power Windows-Refer to «Power Windows Description and Operation»(/cadillac/cts/ii-2007-2014/remont/heated-glassdefoggers/#fixed-and-moveable-windows-system) .
  6. Remote function control-Refer to «Keyless Entry System Description and Operation (with RPO Y41)»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions) or «Keyless Entry System Description and Operation (without RPO Y41)»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-operation) .
  7. Remote Start-Refer to «Keyless Entry System Description and Operation (with RPO Y41)»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions) or «Keyless Entry System Description and Operation (without RPO Y41)»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-operation) .
  8. Retained accessory power (RAP)-Refer to «Retained Accessory Power Description and Operation»(/cadillac/cts/ii-2007-2014/remont/body-electrical/#wiring-systems-and-power-management-description-and-operation) .
  9. Seat belt use sensing-Refer to «Seat Belt System Description and Operation»(/cadillac/cts/ii-2007-2014/remont/restraints-control-systems/#seat-belt-system) .
  10. Theft deterrent-Refer to «Immobilizer Description and Operation (without Y41)»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#immobilizer-system__immobilizer-description-and-operation-without-y41) or «Immobilizer Description and Operation (with Y41)»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#immobilizer-system) and «Content Theft Deterrent (CTD) Description and Operation»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#theft-deterrent-system__content-theft-deterrent-ctd-description-and) .
  11. Wiper/Washer System functions-Refer to «Wiper/Washer System Description and Operation (Wiper and Washers)»(/cadillac/cts/ii-2007-2014/remont/wiperwasher-systems/#wiper-system-and-washer-system) .

Auxiliary Body Control Module (if Equipped)

The export body control system has an additional body control module located in the rear of the vehicle. This additional body control module is referred to as the XBCM. The XBCM has discrete input and output terminals to control additional vehicle body functions not supported by the primary body control module (BCM). The XBCM is wired to the low speed GMLAN serial data bus and the BCM and acts as a gateway between them. If the XBCM does not communicate, various rear end lighting such as rear fog lamps and trailer lighting will be impaired.

The various input and output circuits are described in the corresponding functional areas indicated on the XBCM electrical schematics. Some XBCM functions with the subsystems may be as a gateway only or as an enable for the system. The XBCM related systems/subsystems include, but are not limited to the following

  1. Exterior lighting-Refer to «Exterior Lighting Systems Description and Operation»(/cadillac/cts/ii-2007-2014/remont/exterior-lights/#lighting-system) .
  2. Instrument cluster indicator control-Refer to «Instrument Cluster Description and Operation»(/cadillac/cts/ii-2007-2014/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges) .
  3. Theft deterrent-Refer to «Content Theft Deterrent (CTD) Description and Operation»(/cadillac/cts/ii-2007-2014/remont/door-locks-anti-theft-systems/#theft-deterrent-system__content-theft-deterrent-ctd-description-and) .

Circuit Description

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 bus and the GMLAN low speed bus. 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

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 120 ohms resistors. One of the resistors is located in the rear fuse block, and others are internal to the engine control module (ECM) or powertrain control module (PCM), and the body control module (BCM). The resistors are used to reduce noise on the High Speed GMLAN bus 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. Note: a loss of serial data DTC does not represent a failure of the module that the code is set in.

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 bus is 33.33 Kb/s. This protocol produces a simple pulse train sent out over the GMLAN low speed serial data bus. When a module pulls the bus high, 5 volts, this creates a dominant logic state or 0 on the bus. When the bus 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 bus, a high voltage wake up pulse is sent out over the bus, the voltage level of the pules is +10 volts. Modules connected to the GMLAN low speed bus can be part of a virtual network as described in the previous paragraph. The modules on the GMLAN low speed serial data bus are connected to the bus in a parallel configuration.

Keyword 2000 Circuit Description

The keyword protocols utilize a single wire bi-directional data line between the module and the scan tool. The message structure is a request and response arrangement. The keyword serial data line is used for scan tool diagnostics of the climate control seat module (CCSM) only. Other modules on the vehicle do not exchange data on this circuit.

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 7 Keyword 2000 serial data bus terminal
  6. Pin 14 High speed GMLAN serial data bus (-) terminal
  7. Pin 16 Scan tool power, battery positive voltage terminal

Serial Data Reference

The scan tool communicates over the various buses on the vehicle. When a scan tool is installed on a vehicle, the scan tool will try to communicate with every 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 buses 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
• GMLAN Wiring Repairs
• Window Regulator Motor Programming and Setup
• Electronic Compass Module Replacement (Sedan)
• Antilock Brake System Schematics
• ABS Description and Operation
• Checking Aftermarket Accessories
• Splice Pack Connector End Views
• Rear Compartment Side Trim Panel Replacement
• Instrument Panel Insulator Replacement - Left Side (Left Hand Drive)
• Power Mode Description and Operation
• Audible Warnings Description and Operation
• Exterior Lighting Systems Description and Operation
• Power Windows Description and Operation
• Keyless Entry System Description and Operation (with RPO Y41)
• Keyless Entry System Description and Operation (without RPO Y41)
• Seat Belt System Description and Operation
• Immobilizer Description and Operation (without Y41)
• Immobilizer Description and Operation (with Y41)
• Content Theft Deterrent (CTD) Description and Operation
• Wiper/Washer System Description and Operation (Wiper and Washers)
• DTC B1000
• Data Link References
• Control Module U Code List
• Circuit/System Testing
• Body Control System Description and Operation

More articles — Accessories & Equipment