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Data Communication System: Diagnosis Chevrolet Tahoe III

Communication Devices ~20216 words

DIAGNOSTIC CODE INDEX

DTCDescription
DTC B1000B1000 00: Electronic Control Unit (ECU) Performance No Additional Information Available B1000 04: Side Object Detection Performance - RAM Failure B1000 08: Electronic Control Unit (ECU) Performance Signal Invalid B1000 12: Electronic Control Unit (ECU) Performance Below Minimum Threshold B1000 31: Electronic Control Unit (ECU) General Checksum Problem B1000 32: Electronic Control Unit (ECU) General Memory Failure B1000 33: Electronic Control Unit (ECU) Performance Special Memory Failure B1000 34: Electronic Control Unit (ECU) Performance RAM Integrity B1000 35: Electronic Control Unit (ECU) Performance ROM Integrity B1000 36: Electronic Control Unit (ECU) Performance EEPROM Integrity B1000 37: Electronic Control Unit (ECU) Performance Watchdog / Safety Failure B1000 38: Electronic Control Unit (ECU) Performance Supervision Software Failure B1000 39: Electronic Control Unit (ECU) Performance Internal Electronic Failure B1000 43: Electronic Control Unit (ECU) Performance EEPROM Error B1000 46: Side Object Detection Performance - Invalid Configuration B1000 56: Electronic Control Unit (ECU) Performance Allowable Number of Transitions / Events Exceeded B1000 57: Electronic Control Unit (ECU) Performance B1000 73: Electronic Control Unit (ECU) Performance Parity Error B1000 0F: Electronic Control Unit (ECU) Performance Erratic B1000 2B: Electronic Control Unit (ECU) Performance Missing Reference B1000 2C: Electronic Control Unit Performance Reserved B1000 3B: Electronic Control Unit (ECU) Performance Internal Self Test Failed B1000 3C: Electronic Control Unit (ECU) Performance Internal Communications Failure B1000 4A: Side Object Detection Performance - PROM Checksum Error B1000 F0: Side Object Detection RF Transmit Chain Failed B1000 F1: Side Object Detection RF Receive Chain Failed B1000 F2: Side Object Detection Frequency Calibration Failure B1000 F3: Side Object Detection Inter-Processor Communication Failed
DTC B1001B1001 00: Option Configuration Error B1001 45: Option Configuration Error Variant Not Programmed B1001 46: Option Configuration Error B1001 4B: Option Configuration Error Calibration Not Learned
DTC B101D (HP2 Air Conditioning Control Module)B101D XX: ECU Hardware
DTC B101D (except HP2 A/C Control Module)B101D XX: ECU Hardware
DTC B101EB101E XX: ECU Software
DTC B137AB137A 01: Hybrid Accessory Wake Up Circuit - Short to Battery B137A 06: Hybrid Accessory Wake Up Circuit - Short to Ground or Open
DTC B137BB137B 06: Accessory Power Module Wake Up Circuit - short to ground or open
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 C126C, C126D, C12E3, or U180FC126C: Control Module Communication Bus B Off C126D: Control Module Communication Bus B Off C12E3: Control Module Communication Bus B Off U180F: Control Module Communication Bus B Off
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 U0074U0074 00: Control Module Communication Bus B Off
DTC U0100-U02FF (with HP2)U0100-U02FF (with HP2): Supervised message including transmitter module availability not received.
DTC U0100-U02FF (without HP2)U0100-U02FF (without HP2): Supervised message including transmitter module availability not received.
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 U1500 31: Electronic Control Unit (ECU) Performance General Checksum Failure U1511 00: Inter-device Dedicated Bus Lost Communication With Device 1 U1512 00: Inter-device Dedicated Bus Lost Communication With Device 2
DTC U180FU180F: Control Module Communication Bus B Off
DTC U1812U1812 00: Battery Energy Control Module Bus B High Speed Communication Enable Circuit Low
DTC U1813U1813 00: Battery Energy Control Module Bus B High Speed Communication Enable Circuit High
DTC U1814U1814 00: Powertrain High Speed Communication Enable Circuit
DTC U1815U1815 00: Lost Communication With Drive Motor Control Module "A" on Bus "B"
DTC U1816U1816 00: Lost Communication With Drive Motor Control Module "B" on Bus "B"
DTC U1817U1817 00: Lost Communication With Hybrid Powertrain Control Module on Bus "B"
DTC U1818U1818 00: Lost Communication With ECM/PCM A on Bus B
DTC U1820U1820 00: Lost Communication with Brake System Control Module on Bus B
DTC U1821U1821 00: Lost Communication With DC to DC Converter Control Module A on Bus B
DTC U1826U1826 71: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Invalid Data U1826 72: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Message Counter Incorrect U1826 7F: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Bus Signal Erratic
DTC U1829U1829 00: Lost Communication with Gateway A on Bus B
DTC U182AU182A 00: Lost Communication With Accessory Power Module
DTC U1842U1842: Lost Communication With ECM/PCM
DTC U1843U1843: Lost Communication With ECM/PCM
DTC U1862U1862 00: Battery Energy Control Module Lost Communication with Serial Data Gateway Module
DTC U1866U1866 00: Battery Energy Control Module Lost Communication With Body Control Module
DTC U186AU186A: Lost Communication With Transfer Case Control Module
DTC U186BU186B: Lost Communication With TCM
DTC U1875U1875 00: Drive Motor A Control Module Lost Communication With Battery Energy Control Module
DTC U1876U1876 00: Drive Motor Control Module A Lost Communication With Engine Control Module (ECM)
DTC U1878U1878 00: Drive Motor B Control Module Lost Communication With Battery Energy Control Module
DTC U1879U1879 00: Drive Motor Control Module B Lost Communication With Engine Control Module (ECM)
DTC U1885U1885 00: Battery Energy Control Module Lost Communication With Hybrid Powertrain Control Module
DTC U1886U1886 00: Battery Energy Control Module Lost Communication With Engine Control Module (ECM)/Powertrain Control Module (PCM)
DTC U1888U1888 00: Lost Communication with Battery Pack
DTC U189AU189A 00: DC to DC Converter Control Module A Lost Communication With Hybrid Powertrain Control Module
DTC U2099U2099 00: High Speed Communication Enable Circuit
DTC U209AU209A 00: High Speed Communication Enable Circuit Low
DTC U209DU209D 00: Battery Energy Control Module High Speed Communication Enable Circuit High
DTC U2100U2100 00: Controller Area Network (CAN) Bus Communication
DTC U2103U2103 00: Fewer Controllers On Than Programmed
DTC U2105-U2199U2142 00: Lost Communication With Yaw Rate Sensor (YRS)

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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

The control module has detected an internal malfunction.

The control module refuses all additional inputs.

The DTC can only be cleared with a scan tool.

  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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

The control module has detected an internal malfunction.

The control module refuses all additional inputs.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. This DTC may be stored as a history DTC without affecting the operation of the control module.
  2. 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.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Wake Up SignalB137A 06, *U1812*U1812B137A 01, *U1813
* Sets in the HPCM
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.

A short circuit exists on the wake up signal circuit of the SDG module.

The malfunction indicator lamp (MIL) illuminates and the driver information center (DIC) displays the message Service Hybrid System.

  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.

Circuit/System Testing

WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Failure to follow the procedures exactly as written may result in serious injury or death.
  1. Perform the «High Voltage Disabling»(ref-364532-S04350868292010063000000) procedure.
  2. Reconnect the 12-volt battery.
  3. Ignition OFF, disconnect harness connector X1 of the drive motor generator battery control module and the PIM.
  4. Ignition ON, verify that a test lamp illuminates between the wake up signal circuit of the PIM and ground, and the drive motor generator battery control module and ground as follows: PIM X1 19 BECM X1 12 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 SDG module.
  5. Ignition OFF, verify that a test lamp does not illuminate between the PIM wake up signal circuit terminal 19 and ground. If the test lamp illuminates, test the circuit for a short to voltage. If the circuit tests normal, replace the SDG module.
  6. If all circuits test normal, replace the SDG module.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Wake Up SignalB137B 06U182AU189A
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.

The wake up signal circuit is shorted to ground.

The module is never signaled and the charging system will not operate. The battery indicator will illuminate along with multiple driver information messages.

  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. Ignition OFF, disconnect the harness connector X1 at the APM.
  2. Ignition ON, verify that a test lamp illuminates between the wake up signal circuit terminal 3 and ground. If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.
  3. Ignition OFF and scan tool disconnected, verify that a test lamp does not illuminate between the signal circuit terminal 3 and ground. If the test lamp illuminates, test the circuit for a short to voltage.
  4. If all circuits test normal, replace the APM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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

The module has detected an internal malfunction.

The module refuses all additional inputs.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. This DTC may be stored as a history DTC without affecting the operation of the module.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
  3. If this DTC is retrieved as both a current and history DTC, replace the module that set the DTC.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

Conditions for Running the DTCs

  1. Supply voltage to the modules are in the normal operating range.
  2. The ignition switch in any position other than START.

The module setting the DTC has attempted to establish communications on the PTLAN serial data circuits more than 3 times.

  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.

Verify that DTC U0074 is not set.

  1. If the DTC is set, refer to «DTC U0074»(ref-364513-S11476954412010063000000)
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  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.

  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  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 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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Powertrain High Speed GMLAN Serial Data (+)U0074U0074, U0100-U0299*U0074
Powertrain High Speed GMLAN Serial Data (-)U0074U0074, U0100-U0299*U0074
  1. Supply voltage to the modules are in the normal operating range.
  2. The ignition switch in any position other than START.

The module setting the DTC has attempted to establish communications on the PTLAN serial data circuits more than 3 times.

  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. 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 Powertrain High Speed GMLAN serial data system inoperative. This condition is due to the BCM using both the high and low speed GMLAN systems.
  4. The engine will not start when there is a total malfunction of the Powertrain High Speed GMLAN serial data bus.

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

  1. Attempt to communicate with all control modules on the Powertrain High Speed GMLAN serial data circuit. Communications should not be available with two or more control modules on the Powertrain High Speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only.
  2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
  3. Ignition ON, test for less than 4.5 V between the serial data circuits listed below and ground: Terminal 3 Terminal 11 If greater than the specified range, test the serial data circuit for a short to voltage; refer to Testing the Serial Data Circuits for a Short to Voltage.
  4. Ignition OFF for 60 seconds, test for greater than 100 ohms between the serial data circuit listed below and ground: Terminal 3 Terminal 11 If not the specified value, test the serial data circuit for a short to ground; refer to Testing the Serial Data Circuits for a Short to ground.
  5. Test for 50-70 ohms between the serial data circuit terminal 3 and terminal 11. If less than 35 ohms, test for a short between the serial data circuits; refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance; refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, test the serial data circuits between the DLC and the first connection to the serial data circuit for an open/high resistance.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

DTC Descriptor

Refer to Control Module U Code List .

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U0100-U02FFU0100-U02FF
Module IgnitionU0100-U02FFU0100-U02FF
Module GroundU0100-U02FFU0100-U02FF
Accessory Wake Up Serial DataU1814U0100-U02FF
High Speed GMLAN Serial Data Wake UpU2099U0100-U02FF
High Speed GMLAN Serial Data (+)2U0100-U02FF2
High Speed GMLAN Serial Data (-)2U0100-U02FF2
Low Speed GMLAN Serial Data1U0100-U02FF1
1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with high speed GMLAN device

The 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 turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
  2. A current DTC clears when the malfunction is no longer present.
  3. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
  5. Use «Data Link References»(ref-364513-S10346047942010063000000) 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.
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Before working on any high voltage system, be sure to wear the following Personal Protection Equipment: Safety glasses with appropriate side shields when within 50 feet of the vehicle, either indoors or outdoors. Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors. Visually and functionally inspect the gloves before use. Wear the Insulation gloves at all times when working with the high voltage battery assembly, whether the system is energized or not. Failure to follow the procedures exactly as written may result in serious injury or death.

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

  1. Determine the control module that is not communicating. Refer to «Control Module U Code List»(ref-364513-S36880876902010063000000) .
  2. Using the Hybrid High Voltage Module Chart below, verify that the non-communicating control module is not a high voltage module. If the control module is a high voltage module, perform the «High Voltage Disabling»(ref-364532-S04350868292010063000000) procedure before proceeding with this diagnostic.
  3. If high voltage disabling is required, reconnect the 12 V battery after performing the high voltage disabling procedure.
  4. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
  5. 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.
  6. 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.
  7. 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.
  8. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground. If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  9. 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 control module setting the DTC or a serial data splice pack.
  10. If all circuits test normal, replace the control module that is not communicating.
ModuleVoltage SystemData Link Type
Drive Motor Generator Power Inverter Module (PIM) (Includes Drive Motor Control Module (MCM) 1, 2 and Hybrid Powertrain Control Module (HPCM)300 V 12 VHigh Speed Hybrid GMLAN High Speed GMLAN
Accessory DC Power Control Module (APM)300 V 42 V 12 VHigh Speed Hybrid GMLAN
Transmission Control Module (TCM) (RPO M99)300 V 12 VHigh Speed GMLAN
Air Conditioning Control Module (ACCM) (Part of AC Compressor with HP2)300 V 12 VLow Speed GMLAN
Drive Motor Generator Battery Control Module (BECM)300 V 12 VHigh Speed GMLAN
Power Steering Control Module (PSCM)42 V 12 VHigh Speed GMLAN

Hybrid High Voltage Module Chart

  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

Refer to Control Module U Code List .

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U0100-U02FFU0100-U02FF
Module IgnitionU0100-U02FFU0100-U02FF
Module GroundU0100-U02FFU0100-U02FF
Accessory Wake Up Serial DataU1814U0100-U02FF
High Speed GMLAN Serial Data Wake UpU2099U0100-U02FF
High Speed GMLAN Serial Data (+)2U0100-U02FF2
High Speed GMLAN Serial Data (-)2U0100-U02FF2
Low Speed GMLAN Serial Data1U0100-U02FF1
1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with high speed GMLAN device

The 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 turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
  2. A current DTC clears when the malfunction is no longer present.
  3. A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more control modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
  5. Use «Data Link References»(ref-364513-S10346047942010063000000) 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.

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

  1. Determine the control module that is not communicating. Refer to «Control Module U Code List»(ref-364513-S36880876902010063000000) .
  2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
  3. 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.
  4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground. If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  7. Ignition OFF for 60 seconds, test for less than 5 ohms between the serial data circuit terminals and the 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 control module setting the DTC or a serial data splice pack.
  8. If all circuits test normal, replace the control module that is not communicating.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+ - Window MotorU1511, U1512U1511, U1512
Serial Data - Driver Window Motor, Terminal 5U1500 02U1511U1500 01
Serial Data - Passenger Window Motor, Terminal 5U1500 02U1512U1500 01
Ground - Window MotorU1511 1 , U1512 1
Ignition - Electronic Compass ModuleU1511U1511
Serial Data - Electronic Compass Module, Terminal 3U1511U1511U1511
Ground - Electronic Compass ModuleU1511
1 Either or both DTC may set depending on the location of the open/high resistance.

The system voltage is between 9-16 V.

Compass Malfunction Test

  1. Ignition OFF, disconnect the harness connector at the electronic compass module.
  2. Ignition OFF, test for less than 5.0 ohms 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 circuit terminal 1 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  4. Test for 6.0-7.0 V between the LIN Bus circuit terminal 3 and ground. If greater than the specified range, test the LIN Bus circuit for a short to voltage. If the circuit tests normal, replace the BCM. If less than the specified range, test the LIN Bus 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 ohms 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 V 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 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 door module.
  5. If all circuits test normal, replace the window motor.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  1. Supply voltage to the modules are in the normal operating range.
  2. The ignition switch in any position other than START.

The module setting the DTC has attempted to establish communications on the PTLAN serial data circuits more than 3 times.

  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
SDG Module B+ VoltageU1812, U1821, U1862, U1875, U1878, U1888, U0129U1812, U1821, U1862
Wake Up SignalU1812, *B137A 06U1812U1813, *B137A 01
SDG Module GroundU1812, U1821, U1862
* Sets in the SDG module. No crank, no start. Battery pack contactors are open. drive motor generator battery control module and SDG module will both be inoperative
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.

The drive motor generator battery control module did not receive voltage from the SDG module on the wake up signal circuit.

  1. The driver information center (DIC) displays the message Service Hybrid System.
  2. Multiple DTCs may set depending on the fault location and when the fault occurred.
  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.

A false DTC U1812 can set if the engine does not crank while the ignition key is held in the start position for greater than 3 seconds. Diagnose the engine does not crank condition first.

  1. Ignition OFF, disconnect the inline harness connector X350 at the drive motor generator battery.
  2. Ignition ON, verify that a test lamp illuminates between the wake up signal circuit terminal 10 X350 and ground. If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuit tests normal, replace the SDG module. If the test lamp illuminates, test the wake up signal circuit of the drive motor generator battery control module electrical harness for an open/high resistance.
  3. If all circuits test normal, replace the drive motor generator battery control module.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Wake Up SignalU1812, *B137A 06U1812U1813, *B137A 01
* Sets in the SDG module. No crank, no start. Battery pack contactors are open. drive motor generator battery control module and SDG module will both be inoperative
  1. The system voltage is between 9-18 volts.
  2. Ignition is OFF.

The drive motor generator battery control module receives voltage on wake up signal circuit for greater than 3 seconds when the ignition is OFF.

The hybrid system signals the engine control module (ECM) to request illumination of the malfunction indicator lamp (MIL).

  1. A current DTC clears when the malfunction is no longer present, including a key ON condition when both wake up signals are energized.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

DTC U1813 will always set with SDG module DTC B137A 01.

  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Accessory Wake Up Serial DataU1814U0100-U0299
  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 module(s) is never signaled, therefore the specific subsystem(s) 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.

Short to ground may also set multiple no communication codes for GMLAN high speed modules.

  1. With the ignition OFF, disconnect the module harness connectors listed below one at a time. After each disconnect, retest for current DTCs. DTC U1814 should remain current. Engine control module (ECM) - X1 Transmission control module (TCM) - X1 Transfer case control module (TCCM) (RPO NP8) - X2 Serial data gateway module (SDGM) (RPO HP2) - X2 If the DTC becomes history, replace the module disconnected before the DTC became history.
  2. Ignition OFF, disconnect the X4 harness connector at the BCM.
  3. Test for infinite resistance between the accessory wake up serial data circuit terminal 19 and ground. If less than the specified range, test the serial data circuit for a short to ground.
  4. If the circuit tests normal, replace the BCM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+1U1815/U1816
B+1U1815/U1816
Ignition1U1815/U1816
Module Ground StrapU1815/U18161
High Speed hybrid GMLAN Serial Data (+)U0074U1815/U1816U0074
High Speed hybrid GMLAN Serial Data (-)U0074U1815/U1816U0074
Hybrid Module Wake-up SignalB137AU1815/U1816
1. Multiple symptoms may occur due to open fuses.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur from this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. DTC U1815 can set current in the HPCM, ECM, and the SDGM.
  2. If DTC U1815 is only set in the HPCM, the PIM must be replaced due to all circuits between the HPCM and MCM being internal to the PIM.
  1. Ignition OFF, disconnect the harness connector X1 at the PIM.
  2. Test for less than 5 ohms between the PIM case and ground. If greater than the specified range, test the ground strap for an open/high resistance. If the circuit tests normal, replace the PIM.
  3. Ignition ON, verify that a test lamp illuminates between the following voltage circuit terminals of the PIM and ground. Terminal 6 Terminal 7 Terminal 20 If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the signal circuit terminal 19 and ground. If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the SDGM.
  5. Ignition OFF, disconnect the harness connector X3 at the engine control module.
  6. Test for less than 1.0 ohm on the high speed hybrid GMLAN serial data circuits between the following ECM and PIM circuit terminals. ECM X 3 terminal 53 and PIM X 1 terminal 11 ECM X 3 terminal 33 and PIM X 1 terminal 10 If greater than the specified range, test the circuit for open/high resistance
  7. If all circuits test normal, replace the PIM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+1U1815/U1816
B+1U1815/U1816
Ignition1U1815/U1816
Module Ground StrapU1815/U18161
High Speed hybrid GMLAN Serial Data (+)U0074U1815/U1816U0074
High Speed hybrid GMLAN Serial Data (-)U0074U1815/U1816U0074
Hybrid Module Wake-up SignalB137AU1815/U1816
1. Multiple symptoms may occur due to open fuses.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur from this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to «Instrument Panel Center Trim Panel Replacement (Cadillac)»(ref-364475-S31631395732010063000000) or «Instrument Panel Center Trim Panel Replacement (Except Cadillac)»(ref-364475-S28226219482010063000000) .
  2. DTC U1816 can set current in the HPCM, ECM, and the SDGM.
  3. If DTC U1816 is only set in the HPCM, the PIM must be replaced due to all circuits between the HPCM and MCM being internal to the PIM.
  1. Ignition OFF, disconnect the harness connector X1 at the PIM.
  2. Test for less than 5 ohms between the PIM case and ground. If greater than the specified range, test the ground strap for an open/high resistance. If the circuit tests normal, replace the PIM.
  3. Ignition ON, verify that a test lamp illuminates between the following voltage circuit terminals of the PIM and ground. Terminal 6 Terminal 7 Terminal 20 If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the signal circuit terminal 19 and ground. If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the SDGM.
  5. Ignition OFF, disconnect the harness connector X3 at the engine control module.
  6. Test for less than 1.0 ohm on the high speed hybrid GMLAN serial data circuits between the following ECM and PIM circuit terminals. ECM X 3 terminal 53 and PIM X 1 terminal 11 ECM X 3 terminal 33 and PIM X 1 terminal 10 If greater than the specified range, test the circuit for open/high resistance
  7. If all circuits test normal, replace the PIM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
PTLAN + (circuit 6105)U0074*U1817* **, U189A in HPCM, U182A in SDGMU0074*
PTLAN - (circuit 6106)U0074*U1817* **, U189A in HPCM, U182A in SDGMU0074*
* Other modules/DTCs will set with this fault. ** This DTC may set in the ECM or the SDGM.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur for this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
ECM B+1*1*
ECM Ground1*
PTLAN +U0074*U1818*, U189AU0074*
PTLANU0074*U1818*, U189AU0074*
* Other modules/DTCs will set with this fault. 1. Multiple DTCs including U1818 may set, and multiple symptoms including no start may occur
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur from this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to «Instrument Panel Center Trim Panel Replacement (Cadillac)»(ref-364475-S31631395732010063000000) or «Instrument Panel Center Trim Panel Replacement (Except Cadillac)»(ref-364475-S28226219482010063000000) .
  2. If the ECM is inoperative due to an open in the voltage or ground circuits then DTC U0100 will be set current in the power steering control module (PSCM).
  3. Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.
  1. Ignition OFF, disconnect harness connector X1 of the APM and the EBCM.
  2. Test for less than 1.0 ohm between the APM and the EBCM on the following circuit terminals. PTLAN + APM terminal 5 and EBCM terminal 33 PTLAN - APM terminal 1 and EBCM terminal 21 If greater than the specified range, test the circuit for an open/high resistance.
  3. Ignition OFF, disconnect harness connector X1 of the SDGM.
  4. Test for less than 1.0 ohm between the EBCM and the SDGM on the following circuit terminals. PTLAN + EBCM terminal 34 and SDGM terminal 13 PTLAN - EBCM terminal 22 and SDGM terminal 11 If greater than the specified range, test the circuit for an open/high resistance.
  5. If the circuits test normal, replace the SDGM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Ignition Voltage (circuit 948)U1820*, U189A in HPCM, U1818 in SDGMU1820*, U189A in HPCM, U1818 in SDGM
Ground (circuit 950)U1820*, U189A in HPCM, U1818 in SDGM
PTLAN + (circuit 6105)U0074*U1820*, U189A in HPCM, U1818 in SDGMU0074*
PTLAN - (circuit 6106)U0074*U1820*, U189A in HPCM, U1818 in SDGMU0074*
* Other modules/DTCs will set with this fault.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur for this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Verify the following DTCs are not set in the modules as follows: SDGM - U1818 HPCM - U189A If any listed DTC is present, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-364486-S07394808542010063000000) to diagnose that DTC prior to this diagnostic.
  2. Ignition OFF, disconnect the harness connector of the yaw rate and lateral acceleration sensor.
  3. Verify that a test lamp illuminates between the ground circuit terminal 6 and B+. If the test lamp does not illuminate, test the circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the EBCM.
  4. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal 1 and ground. If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.
  5. Ignition OFF, disconnect harness connector X1 of the SDGM.
  6. Test for less than 1.0 ohm between the SDGM and the yaw rate and lateral acceleration sensor on the following circuit terminals. PTLAN + SDGM terminal 14 and yaw rate and lateral acceleration sensor terminal 2 PTLAN - SDGM terminal 12 and yaw rate and lateral acceleration sensor terminal 3 If greater than the specified range, test the circuit for an open/high resistance.
  7. If the circuits test normal, replace the SDGM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U1821*U1821
GroundU1821*
PTLAN +U0074*U1821, 1U0074*
PTLANU0074*U1821, 1U0074*
* Other modules/DTCs may set with this fault. 1. Multiple DTCs including U1821 may set and multiple symptoms including a no start condition may occur.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur from this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

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

Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.

  1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to «High Voltage Disabling»(ref-364532-S04350868292010063000000) .
  2. Ignition OFF, disconnect harness connector X4 of the accessory DC power control module.
  3. Test for less than 1.0 ohm between the accessory DC power control module connector terminal and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
  4. Ignition ON, disconnect harness connector X3 of the accessory DC power control module.
  5. Verify that a test lamp illuminates between the accessory DC power control module connector terminal A and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Ignition OFF, disconnect harness connector X1 of the accessory DC power control module and the drive motor generator power inverter module.
  7. Test for less than 1.0 ohm at the accessory DC power control module connector and drive motor generator power inverter module connector between the following connector serial data terminals. Accessory DC power control module terminal 1 and drive motor generator power inverter module terminal 24 Accessory DC power control module terminal 2 and drive motor generator power inverter module terminal 25 If greater than the specified value, test the serial data circuits for an open/high resistance.
  8. Test for infinte resistance between the accessory DC power control module terminal 2 and accessory DC power control module terminal 1. If less than the specified value, test the serial data circuits for a short between the circuits.
  9. If all circuits test normal, replace the accessory DC power control module.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Yaw and Lateral Accelerometer Sensor 12 V Reference11
Yaw and Lateral Accelerometer Sensor CAN Bus High Serial DataU1826 71, U1826 72, U1826 7FU1826 7F
Yaw and Lateral Accelerometer Sensor CAN Bus Low Serial DataU1826 71, U1826 72, U1826 7FU1826 7F
Yaw and Lateral Accelerometer Sensor Ground1
1. Circuit Inoperative
  1. The system voltage is between 9-16 V.
  2. The vehicle power mode master requires serial data communication to occur.

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

  1. The vehicle stability enhancement system (VSES), if equipped, and traction control system (TCS) will not function.
  2. System OFF lamps will illuminate for these systems.
  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.
  1. Ignition OFF, disconnect the harness connector at the Yaw and Lateral Accelerometer Sensor.
  2. Test for less than 5 ohms between the Yaw and Lateral Accelerometer Sensor ground circuit terminal 6 and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the Yaw and Lateral Accelerometer Sensor voltage (12 V reference) circuit terminal 1 and ground. If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM.
  4. Ignition OFF, disconnect the harness connector at the EBCM
  5. Test for less than 1 ohms in each serial data circuit between the Yaw and Lateral Accelerometer Sensor and the EBCM. Yaw and Lateral Accelerometer Sensor serial data circuit terminal 2 and EBCM serial data circuit terminal 33 Yaw and Lateral Accelerometer Sensor serial data circuit terminal 3 and EBCM serial data circuit terminal 21 If greater than the specified value, test the Yaw and Lateral Accelerometer Sensor serial data circuits terminals 2 and 3 for an open/high resistance.
  6. If all circuits test normal, replace the Yaw and Lateral Accelerometer Sensor.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
APM B+U182A*U182A*
APM Wake Up SignalU182A, B137B*U182A*U189A*
APM Powertrain Serial Data (+)U0074*U0074*U0074*
APM Powertrain Serial Data (+)U0074*U0074*U0074*
PIM B+U1829*U1829*
PIM IgnitionP2534*P2534*U209A*, B1453
PIM Wake Up SignalB137A*U1829*U189A*
PIM Powertrain Serial Data (+)U0074*U0074*U0074*
PIM Powertrain Serial Data (-)U0074*U0074*U0074*
* Other modules/DTCs will set with this fault.
  1. The system voltage is between 9-16 V.
  2. The ignition in RUN.

The powertrain serial data circuits between the SDGM and the APM or the PIM are open.

The control modules is never signaled, therefore the specific subsystems may not function. Depending on the fault, the MIL, battery indicator may illuminate and several DIC messages may be present.

  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. Circuits to the HPCM are diagnosed only to the PIM connector because the HPCM is replaced as part of the PIM.
  2. Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.

APM

  1. Ignition OFF, test for less than 1.0 ohms between the accessory DC power control module case and ground strap. If greater than the specified value, test the ground circuit for an open/high resistance.
  2. Disconnect harness connector X3 of the accessory DC power control module.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the control circuits of the accessory DC power control module for a short to ground.
  4. Ignition OFF, disconnect harness connector X1 of the accessory DC power control module.
  5. Ignition ON, verify that a test lamp illuminates between the wake up signal circuit terminal 3 and ground. If the test lamp does not illuminate, test the wake up signal circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the serial data gateway module.
  6. If all circuits test normal, replace the accessory DC power control module.

PIM

  1. Ignition OFF, disconnect harness connector X1 of the drive motor generator power inverter module (PIM).
  2. Ignition ON, verify that a test lamp illuminates between each B+ circuit and ground. If the test lamp does not illuminate, test each B+ circuit for an open/high resistance. If the circuit fuse is open, test the control circuits of the PIM for a short to ground.
  3. Verify that a test lamp illuminates between the ignition circuit terminal 20 and ground. If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. If the circuit fuse is open, test the control circuits of the PIM for a short to ground.
  4. Verify that a test lamp illuminates between the wake up signal circuit terminal 19 and ground. If the test lamp does not illuminate, test the wake up signal circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the serial data gateway module.
  5. If all circuits test normal, replace the drive motor generator power inverter module.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+U182A*U182A*
Wake Up SignalU182A, B137B*U182A*U189A*
Powertrain Serial Data (+)U0074*U0074, U182A*U0074*
Powertrain Serial Data (-)U0074*U0074, U182A*U0074*
* Other modules/DTCs will set with this fault.
  1. The system voltage is between 9-16 V.
  2. The ignition in RUN.
  1. The APM wake up signal is open.
  2. The APM does not receive battery voltage.
  3. The powertrain serial data circuits between the SDGM and the APM are open.

The modules is never signaled, therefore the specific subsystems may not function. Depending on the fault, the MIL, battery indicator may illuminate and several DIC messages may be present.

  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. When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to «Instrument Panel Center Trim Panel Replacement (Cadillac)»(ref-364475-S31631395732010063000000) or «Instrument Panel Center Trim Panel Replacement (Except Cadillac)»(ref-364475-S28226219482010063000000) .
  2. Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.
  1. Ignition OFF, test for less than 1.0 ohms between the accessory DC power control module case and ground strap. If greater than the specified value, test the ground circuit for an open/high resistance.
  2. Disconnect harness connector X3 of the accessory DC power control module.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the control circuits of the accessory DC power control module for a short to ground.
  4. Ignition OFF, disconnect harness connector X1 of the accessory DC power control module.
  5. Ignition ON, verify that a test lamp illuminates between the wake up signal circuit terminal 3 and ground. If the test lamp does not illuminate, test the wake up signal circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the serial data gateway module.
  6. If all circuits test normal, replace the accessory DC power control module.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master indicates that the need for serial data communications.

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

  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master indicates that the need for serial data communications.

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

  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
SDG Module B+ Voltage*U1862, U1888, U1878, U1875, U1821, U1812, U0129U1862, U1821, U1812
SDG Module Serial Data Communication EnableU1862U1862
High Speed GMLAN Serial Data Bus*U1862, U1888, U1886, U1885, U1879, U1878, U1876, U1875, U1866, U0140, U0129, U0102, U0101, U0100*U1888, U1878, U8175, U0129*U1862, U1888, U1886, U1885, U1879, U1878, U1876, U1875, U1866, U0140, U0129, U0102, U0101, U0100
High Speed GMLAN Serial Data Bus*U1862, U1888, U1886, U1885, U1879, U1878, U1876, U1875, U1866, U0140, U0129, U0102, U0101, U0100*U1888, U1878, U8175, U0129*U1862, U1888, U1886, U1885, U1879, U1878, U1876, U1875, U1866, U0140, U0129, U0102, U0101, U0100
SDG Module GroundU1862, U1821, U1812
Drive Motor Generator Battery Control Module B+ Voltage*U1862, U1888, U1878, U1875, U1821, U1812, U0129**U1888, U1878, U1875, U0129
* No crank, no start. Battery pack contactors are open. drive motor generator battery control module and SDG module will both be inoperative. ** No crank, no start. Battery pack contactors are open. drive motor generator battery control module is inoperative.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur from the drive motor generator battery control module via the SDG module.

A supervised periodic message that includes the SDG module availability has not been received by the drive motor generator battery control module.

  1. The charging system will not operate properly and the vehicle battery will discharge as the vehicle is driven.
  2. The driver information center (DIC) displays the message Service Hybrid System.
  3. Multiple DTCs may set depending on the fault location and when the fault occurred.
  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. If the SDG module becomes inoperative, the drive motor generator battery control module will set DTC U1862 and other modules will set loss of communication DTCs against the SDG module.
  2. If serial data is lost between the SDG module and the drive motor generator battery control module multiple modules will set loss of communication DTCs against the drive motor generator battery control module.
  1. Ignition OFF, disconnect the harness connector X2 at the SDG module.
  2. Ignition OFF and the scan tool disconnected, open and close the driver door, and wait 1 minute.
  3. Test for less than 5.0 ohms between the ground circuit terminal 18 X2 and ground. If greater than the specified range, test the circuit for an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 8 X2 and ground. If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.
  5. Test for 10.5-12.5 volts between the serial data communication enable circuit terminal 16 X2 and ground. If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable communication/control module.
  6. Ignition OFF, connect the harness connector X2 to the SDG module.
  7. Ignition OFF, disconnect the harness connector X1 at the SDG module.
  8. Ignition ON, test for 2.1-2.5 volts between the high speed GMLAN serial data bus low circuit terminal listed below and ground: Terminal 15 X1 Terminal 16 X1 If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the applicable communication/control module. If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable communication/control module.
  9. If all circuits test normal, replace the SDG module.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BCM B+U1866*, U0140 in EBCMU1866*, U0140 in EBCM
BCM GroundU1866*, U0140 in EBCM
HSGMLAN + (circuit 2500)1*U1866*, U0140 in EBCM1*
HSGMLAN - (circuit 2501)1*U1866*, U0140 in EBCM1*
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master indicates that the need for serial data communications.

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

  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master indicates that the need for serial data communications.

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

  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BECM B+ (circuit 4240)U0146* in PSCMU1875* in HPCM, U0111 in SDGM
BECM Ground (circuit 2751)U1875* in HPCM, U0111 in SDGM
BECM Communication Enable Signal (circuit 5986)U1875* in HPCM, U2099 in BCMU1875* in HPCM, U0111 in SDGM
HSGMLAN + (circuit 2500)1*U1875* in HPCM, U0111 in SDGM1*
HSGMLAN - (circuit 2501)1*U1875* in HPCM, U0111 in SDGM1*
HPCM Ignition (circuit 2139)P2534P2534U1875* in HPCM, B1453 in SDGM
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
ECM B+U1876*, U0100 in HPCMU1876*, U0100 in HPCM
ECM GroundU1876*, U0100 in HPCM
ECM Wake Up Signal (circuit 5985)U1876* in HPCM, U1814 in BCMU1876*, U0100 in HPCM
HSGMLAN + (circuit 2500)1*U1876*, U0100 in HPCM1*
HSGMLAN - (circuit 2501)1*U1876*, U0100 in HPCM1*
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
BECM B+ (circuit 4240)U0146* in PSCMU1878* in HPCM, U0111 in SDGM
BECM Ground (circuit 2751)U1878* in HPCM, U0111 in SDGM
BECM Communication Enable Signal (circuit 5986)U1878* in HPCM, U2099 in BCMU1878* in HPCM, U0111 in SDGM
HSGMLAN + (circuit 2500)1*U1878* in HPCM, U0111 in SDGM1*
HSGMLAN - (circuit 2501)1*U1878* in HPCM, U0111 in SDGM1*
HPCM Ignition (circuit 2139)P2534P2534U1875* in HPCM, B1453 in SDGM
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
ECM B+U1879*, U0100 in HPCMU1879*, U0100 in HPCM
ECM GroundU1879*, U0100 in HPCM
ECM Wake Up Signal (circuit 5985)U1879* in HPCM, U1814 in BCMU1879*, U0100 in HPCM
HSGMLAN + (circuit 2500)1*U1879*, U0100 in HPCM1*
HSGMLAN - (circuit 2501)1*U1879*, U0100 in HPCM1*
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
HSGMLAN + (circuit 2500)U0073*U1885*U0073*
HSGMLAN - (circuit 2501)U0073*U1885*U0073*
* Other modules/DTCs will set with this fault.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur from this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

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

Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.

  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
ECM B+U1886*, U0100 in HPCMU1886*, U0100 in HPCM
ECM GroundU1886*, U0100 in HPCM
ECM Wake Up Signal (circuit 5985)U1886* in HPCM, U1814 in BCMU1886*, U0100 in HPCM
HSGMLAN + (circuit 2500)1*U1886*, U0100 in HPCM1*
HSGMLAN - (circuit 2501)1*U1886*, U0100 in HPCM1*
* Other modules/DTCs will set with this fault. 1. Scan tool does not communicate with high speed GMLAN device.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

The modules is never signaled, therefore the specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Drive Motor Generator Battery Control Module B+ VoltageU1888, U1878, U1875, U1862, U1821, U1812, U0129, *U0111U1888, U1878, U1875, *U0111
Drive Motor Generator Battery Control Module Serial Data Communication EnableU1888, U1878, U1875, *U209AU1888, U1878, U1875, *U0111
High Speed GMLAN Serial Data Bus +**U1888U1888, U1878, U1875, U0129, *U0111**U1888
High Speed GMLAN Serial Data Bus**U1888U1888, U1878, U1875, U0129, *U0121, *U0111**U1888
Drive Motor Generator Battery Control Module GroundU1888, U1878, U1875, *U0111
HPCM Ignition (circuit 2139)P2534P2534U1888, *B1453
* Sets in the SDG module ** No scan tool communication with hard fault. Additionl DTCs are set
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur fro this specific module.

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

  1. The driver information center (DIC) displays the message Service Hybrid System.
  2. Multiple DTCs may set depending on the fault location and when the fault occurred.
  3. The vehicle will not start or run because the 300 volt battery contactors are OPEN.
  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. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
PTLAN + 2 circuits at PIMU0074*U189A*U0074*
PTLAN - 2 circuits at PIMU0074*U189A*U0074*
Wake Up Signal circuit 968B137A* in SDGMU189A* **1
Wake Up Signal circuit 932B137B*U182A*U189A*
Wake Up Signal Circuit 5985U1814* in BCMU1812* in HPCMU209A* in SDGM
* Other modules/DTCs will set with this fault. ** Open at SDGM or BECM will set DTC U1812 in HPCM. Open at PIM will set DTC U189A in the HPCM. 1. Parasitic drain on battery, and may set DTC U1875, U1876, U1878, U1879 as history in the HPCM with the key ON, or as current with the key OFF.
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.
  1. The HPCM does not receive voltage from the SDGM on the wake up signal circuit.
  2. The wake up circuit between the SDGM and the APM is shorted to voltage.
  3. Any of the 4 PTLAN circuits connected to the HPCM are open.

The modules is never signaled, therefore the specific subsystems may not function. Depending on the fault, the MIL, battery indicator may illuminate and several DIC messages be present.

  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. When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to «Instrument Panel Center Trim Panel Replacement (Cadillac)»(ref-364475-S31631395732010063000000) or «Instrument Panel Center Trim Panel Replacement (Except Cadillac)»(ref-364475-S28226219482010063000000) .
  2. Circuits to the HPCM are diagnosed only to the PIM connector because the HPCM is replaced as part of the PIM.
  3. Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.
  1. Ignition OFF, disconnect harness connector X1 of the APM.
  2. Test for less than 0.5 volts between the wake up signal circuit terminal 3 and ground. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the SDGM.
  3. Disconnect harness connector X1 of the PIM.
  4. Test for B+ between the wake up signal circuit terminal 19 and ground. If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the SDGM.
  5. Test for less than 1.0 ohm between the APM and the PIM on the following circuit terminals. PTLAN + APM terminal 2 and PIM terminal 25 PTLAN - APM terminal 1 and PIM terminal 24 If greater than the specified range, test the circuit for an open/high resistance.
  6. Ignition OFF, disconnect harness connector X3 of the engine control module (ECM).
  7. Test for less than 1.0 ohm between the APM and the ECM on the following circuit terminals. PTLAN + APM terminal 11 and ECM terminal 53 PTLAN - APM terminal 10 and ECM terminal 33 If greater than the specified range, test the circuit for an open/high resistance.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using the diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) 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. ** History only. If cleared the DTC will return after several ignition cycles.
  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.

Short to ground will also set multiple history no communication codes for GMLAN high speed modules

WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Failure to follow the procedures exactly as written may result in serious injury or death.
  1. With the ignition OFF, disconnect the module harness connectors listed below, if equipped, one at a time. After each disconnect, retest the BCM for current DTCs. DTC U2099 should remain current. Drive motor generator battery control module (BECM) (RPO HP2) - X 1 Electronic brake control module (EBCM) - X 1 Electronic suspension control (ESC) module - X 1 Fuel pump flow control module (FPCM) - X 1 Power steering control module (PSCM) (RPO HP2) - X 1 If the DTC becomes history, replace the module disconnected before the DTC became history.
  2. Perform the «High Voltage Disabling»(ref-364532-S04350868292010063000000) procedure.
  3. Ignition OFF, disconnect harness connector X1 of the BECM.
  4. Reconnect the 12-volt battery.
  5. Test the BCM for current DTCs. DTC U2099 should remain current. If the DTC becomes history, replace the BECM.
  6. Ignition OFF, disconnect the harness connector X 3 at the BCM.
  7. With the above harness connectors still disconnected, test for infinite resistance between the high speed GMLAN serial data wake up circuit terminal 19 and ground. If less than the specified value, test the wake up circuit for a short to ground.
  8. If all circuits test normal and DTC is current, replace the BCM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Ignition Voltage (Circuit 2139)P2534* **P2534**U209A** or B1453
Ignition Voltage (Circuit 239)B1453* **B1453**U209A** or B1453
Communication Enable Signal (Circuit 5986)U209A** or U2099U209A**
Wake Up Signal (Circuit 5985)U1814*U1812*U209A*
* Circuit fuse will open ** May set other module/DTCs.
  1. The system voltage is between 9-16 volts.
  2. The ignition key is OFF.
  1. The communication enable signal circuit is open/high resistance.
  2. The wake up signal circuit is shorted to voltage.

The MIL may illuminate and the DIC may display multiple messages.

  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.

When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to Instrument Panel Center Trim Panel Replacement (Cadillac) or Instrument Panel Center Trim Panel Replacement (Except Cadillac) .

  1. Ignition OFF, disconnect the harness connector X2 at the SDGM.
  2. Verify less than 0.5 volts between the wake up signal circuit terminal 19 and ground. If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  3. Ignition ON, verify B+ between the communication enable signal circuit terminal 16 and ground. If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, replace the SDGM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Wake Up Signal (circuit 5986)U209A in SDGM or U2099 in BCMU209A*U209D**
* Other modules will set other DTC with this fault. ** Will set DTC U209D as current with the key OFF, and as history with the key ON. Will also likely cause a parasitic drain on battery.
  1. The system voltage is between 9-18 volts.
  2. Ignition key OFF.

The BECM receives voltage from the BCM on wake up signal circuit 5986 for 3 seconds with the ignition OFF.

The hybrid powertrain control module (HPCM) will set DTC U209D.

  1. A current DTC clears when the malfunction is no longer present, including a key ON condition when both wake up signals are energized.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. DTC U209D will only set as current with the ignition in the OFF position. It will become history when the ignition is turned ON.
  2. When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to «Instrument Panel Center Trim Panel Replacement (Cadillac)»(ref-364475-S31631395732010063000000) or «Instrument Panel Center Trim Panel Replacement (Except Cadillac)»(ref-364475-S28226219482010063000000) .
  3. Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.
WARNINGAlways perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed. The High Voltage Disabling procedure will perform the following tasks: Identify how to disable high voltage. Identify how to test for the presence of high voltage. Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. Failure to follow the procedures exactly as written may result in serious injury or death.
  1. Perform the «High Voltage Disabling»(ref-364532-S04350868292010063000000) procedure.
  2. Ignition OFF, disconnect harness connector X1 of the BECM.
  3. Reconnect the 12-volt battery.
  4. Ignition OFF and scan tool disconnected, test for less than 1 volt between wake up signal terminal 13 and ground. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

Circuit Description

The GMLAN serial data circuits are controller area network (CAN) serial data buses used to communicate information between the control modules. Typical data transmission speeds must be high enough to ensure that a required real-time response is maintained. On this vehicle there are 2 totally different types of GMLAN serial data circuits, the high speed 2-wire circuit and low speed single wire circuit. Refer to Data Link Communications Description and Operation for the complete description of these buses. The GMLAN serial data circuits also communicate directly to the DLC connector. Messages are interpreted by the externally connected CANdi module which acts as a transceiver for the scan tool.

Modules connected to the GMLAN serial data circuits monitor communications during normal vehicle operation, where operation information is exchanged among the modules. All the modules on the GMLAN networks, maintain a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages. If the TEC value exceeds 255, the controller removes itself from the network and DTC U2100 will result.

  1. Supply voltage to the modules are in the normal operating range.
  2. The vehicle is in the RUN power mode.

The module setting the DTC has attempted to establish communications on the GMLAN circuits for more than 7 times.

  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 cannot be retrieved with a current status. Diagnosis of a current DTC is accomplished via the symptom, «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-364513-S21001330252010063000000) , or «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(ref-364513-S36708622582010063000000) depending on the module serial data communication.
  2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-364513-S21001330252010063000000) , or «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(ref-364513-S36708622582010063000000) procedure in order to isolate an intermittent condition.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.

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

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

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

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

The module uses a default value for the missing parameter.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
  1. Diagnosis of this DTC is accomplished via the symptom, «DTC U0100-U02FF (with HP2)»(ref-364513-S41867333272010063000000) or «DTC U0100-U02FF (without HP2)»(ref-364513-S22621777342010063000000) .
  2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the «DTC U0100-U02FF (with HP2)»(ref-364513-S41867333272010063000000) or «DTC U0100-U02FF (without HP2)»(ref-364513-S22621777342010063000000) procedure in order to isolate an intermittent condition.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
  1. 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 has not been received.

  1. The vehicle stability enhancement system (VSES), if equipped, and traction control system (TCS) will not function.
  2. System OFF lamps will illuminate for these systems.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: A control module on the data communication circuit was disconnected while the communication circuit is awake. Power to one or more modules was interrupted during diagnosis. A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time. If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
  2. A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
  3. Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
  4. Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
  5. Use to determine if the module uses high or low speed GMLAN serial data communications.
  6. Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.
  7. This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module.
  1. Ignition OFF, disconnect the harness connector of the yaw rate sensor.
  2. Ignition ON, verify that a test lamp illuminates between the module voltage circuit and ground. If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM.
  3. Ignition OFF, test for less than 5 ohms between the module ground circuits and ground. If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.
  4. If all circuits test normal, replace the yaw rate sensor.

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(ref-364488-S07680217832010063000000) .
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

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»(ref-364513-S30773421552010063000000)
  2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-364513-S21001330252010063000000)
  3. «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(ref-364513-S36708622582010063000000)
  4. «Scan Tool Does Not Communicate with Powertrain High Speed GMLAN Device»(ref-364513-S06832283842010063000000)
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) 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
  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.
  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.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) 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
  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.

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»(ref-364513-S10346047942010063000000) . Communications should not be available with two or more control modules on the high speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only; refer to «DTC U0100-U02FF (with HP2)»(ref-364513-S41867333272010063000000) or «DTC U0100-U02FF (without HP2)»(ref-364513-S22621777342010063000000) .
  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.
  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.
  6. Test for 50-70 ohms between the serial data circuits terminal 6 and terminal 14. If less than 35 ohms, test for a short between the serial data circuits; refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance; refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, 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
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) 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 200, 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
  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.

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»(ref-364513-S10346047942010063000000) . Communications should not be available with two or more control modules on the low speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only, refer to «DTC U0100-U02FF (with HP2)»(ref-364513-S41867333272010063000000) or «DTC U0100-U02FF (without HP2)»(ref-364513-S22621777342010063000000) . If one or more control modules are communicating but not all, refer to Testing the Serial Data Circuit for an Open/High Resistance.
  2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
  3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuit terminal 1 and ground. If greater than the specified range, test the serial data circuit for a short to voltage, refer to Testing the Serial Data Circuit for a Short to Voltage.
  5. Ignition OFF for 60 seconds, test for greater than 100 ohms between the serial data circuit terminal 1 and ground. If not the specified value, test the serial data circuit for a short to ground, refer to Testing the Serial Data Circuits for a Short to ground.
  6. Disconnect the harness connector at the JX 200 splice pack.
  7. Test for less than 2 ohms between the serial data circuit terminal 1 and the JX 200 splice pack terminal D. 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 200, JX 300, and JX 201 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 200, JX 300, and JX 201 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 300 splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the JX 300 splice pack. If all control modules on the JX 300 spice pack do not communicate, test the serial data circuit between the JX 200 and JX 300 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 200 if the control modules not communicating are connected to the JX 200 splice pack JX 201 if the control modules not communicating are connected to the JX 201 splice pack, if equipped JX 300 if the control modules not communicating are connected to the JX 300 splice pack
  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.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-364486-S08087544882010063000000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-364486-S25727745392010063000000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-364486-S17107648382010063000000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Powertrain High Speed GMLAN Serial Data (+)1U0100-U0299*1
Powertrain High Speed GMLAN Serial Data (-)1U0100-U0299*1
Ground (DLC, terminal 5)1
* No communications with one or more Powertrain High Speed GMLAN modules. An open in only one Powertrain 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 Powertrain High Speed GMLAN module
  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 Powertrain 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 Powertrain 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.

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

  1. Attempt to communicate with all control modules on the Powertrain High Speed GMLAN serial data circuit, refer to «Data Link References»(ref-364513-S10346047942010063000000) . Communications should not be available with two or more control modules on the Powertrain High Speed GMLAN serial data circuit. If only one control module is not communicating, diagnose that control module only; refer to «DTC U0100-U02FF (with HP2)»(ref-364513-S41867333272010063000000) or «DTC U0100-U02FF (without HP2)»(ref-364513-S22621777342010063000000) .
  2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
  3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 ohms between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for less than 4.5 V between the serial data circuits listed below and ground: Terminal 3 Terminal 11 If greater than the specified range, test the serial data circuit for a short to voltage; refer to Testing the Serial Data Circuits for a Short to Voltage.
  5. Ignition OFF for 60 seconds, test for greater than 100 ohms between the serial data circuits listed below and ground: Terminal 3 Terminal 11 If not the specified value, test the serial data circuit for a short to ground; refer to Testing the Serial Data Circuits for a Short to ground.
  6. Test for 50-70 ohms between the serial data circuits terminal 3 and terminal 11. If less than 35 ohms, test for a short between the serial data circuits; refer to Testing the Serial Data Circuits for a Short between the Circuits. If 35-50 ohms there may be a third terminating resistor between the serial data circuits. This can happen if the incorrect control module is installed. Some control modules are available with and without the terminating resistors installed to reduce the need of terminating resistors in the wiring harness. If greater than 70 ohms but less than infinite, test the serial data circuit for an open/high resistance; refer to Testing the Serial Data Circuits for an Open/High Resistance. If infinite, test the serial data circuits between the DLC and the first connection to the serial data circuit for an open/high resistance.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition OFF, disconnect the harness connectors with the Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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 Powertrain 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

The communication among control modules is performed through the high speed GMLAN serial data bus, the low speed GMLAN serial data bus, and with RPO HP2 the high speed hybrid GMLAN serial data bus. The modules that need real time communication are attached to the high speed GMLAN busses. There are several modules that act as the gateway module or translator for communication between the various serial data busses. With RPO HP2 the serial data gateway module (SDGM) is the gateway and on all others the body control module (BCM). All high speed modules are activated by a communication enable or wakeup circuit from another module as determined by the power mode master (PMM).

Refer to Data Communication Schematics to determine the circuit and module that activates specific high speed modules.

Signal supervision is the process of determining whether an expected signal is being received or not. Some messages are sent on a periodic basis and are interpreted as a heartbeat of a device. If such a signal is lost, the signal supervision part of the software will set a no communication DTC (U. code) against the missing device. This code is mapped on the Tech 2 screen as a code against the physical device. A lost communication DTC typically is set in modules other than the module with a communication failure.

High Speed GMLAN Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data modules. The serial data is transmitted on 2 twisted wires that allow speed up to 500 Kb/s. The twisted pair is terminated with two 120-ohm resistors, one is internal to the engine control module (ECM) and the other is after the electronic brake control module (EBCM), or if equipped, the suspension control module. 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 1 volt to the high speed GMLAN serial data bus (+) and subtracts 1 volt from the high speed GMLAN serial data bus (-) wire. If a communication signal is lost, the application will set a no communication code against the respective control module. 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.

The high speed GMLAN serial data allows communication between the body control module (BCM), ECM, transmission control module (TCM), vehicle communication interface module (VCIM), 4WD control module, EBCM, and the suspension control module depending on RPO.

High Speed Hybrid GMLAN Circuit Description

The high speed hybrid GMLAN serial data modules do not communicate directly with the scan tool. The SDGM communicates on all serial data busses and relays the high speed hybrid GMLAN serial data information to the scan tool. The high speed hybrid GMLAN serial data bus operates the same as the high speed GMLAN bus with the exception of the need of the SDGM for communication between the modules and a scan tool.

Low Speed GMLAN 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. 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 low speed GMLAN serial data bus. When a module pulls the bus high, 5 volts, this creates a logic state of 0 on the bus. When the bus is pulled low, 0 volts, it is translated as a logic state of 1. To wake the control modules connected to the low speed GMLAN serial data bus, a wake up signal is sent out over the bus. Modules connected to the low speed GMLAN bus can be part of a virtual network as described in the other GMLAN circuit descriptions above. The modules on the low speed GMLAN serial data bus are connected to the bus using several splice or "star" connectors separating groups of modules. The following lists state the splices and modules connected to the low speed serial data circuits

I/P Splice

  1. Data link connector (DLC), connected only to the instrument panel (I/P) splice
  2. Amplifier (Amp)
  3. Rear seat audio (RSA)
  4. Vehicle communication interface module (VCIM)
  5. Digital radio receiver (DRR)
  6. Inside rearview mirror module (ISRVM), connected through the mid I/P fuse block
  7. Instrument panel cluster (IPC)
  8. Body control module (BCM)
  9. Theft deterrent module (TDM)
  10. Heater ventilation and air conditioning (HVAC)
  11. Radio
  12. Driver door switch (DDS), connected through the left I/P fuse block
  13. Passenger door switch (PDS), connected through the right I/P fuse block

Body Splice

  1. Articulating running board module (ARBM)
  2. Ultrasonic park assist (UPA)
  3. Memory seat module (MSM)
  4. Liftgate module (LGM)
  5. Passenger presence system (PPS)
  6. Inflatable restraint vehicle rollover sensor (ROS)
  7. Inflatable restraint sensing and diagnostic module (SDM)

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