Home ReviewsRefund
Home/Hummer/H2/Hummer H2 I рестайлинг (2007-2009)/Repair manual/Communication Devices/Data Communications: Diagnosis
Contents Section: Communication Devices All sections

Data Communications: Diagnosis Hummer H2 I рестайлинг

Communication Devices ~4670 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 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 F0: Side Object Detection RF Transmit Chain Failed B1000 F1: Side Object Detection RF Receive Chain Failed
DTC B1001B1001 00: Option Configuration Error B1001 45: Option Configuration Error Variant Not Programmed B1001 46: Option Configuration Error B1001 4B: Option Configuration Error Calibration Not Learned
DTC B1009B1009: EEPROM Checksum Mismatch/Error
DTC B1016B1016 00: VIN Not Programmed
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 U0020U0020 00: Low Speed CAN Communication Bus Performance
DTC U0073 or U2100U0073 00: Control Module Communication Bus Off U0073 71: ECU HS Bus Off U0073 72: ECU LS Bus Off U2100 00: Controller Area Network (CAN) Bus Communication U2100 47: Controller Area Network (CAN) Bus Communication
DTC U0100-U0299U0100 00: Lost Communication With ECM/PCM U0100 75: Lost Communication With ECM/PCM U0100 7F: Lost Communication With ECM/PCM U0101 00: Lost Communication With TCM U0102 00: Lost Communication With Transfer Case Control Module U0104 00: Lost Communication With Cruise Control Module U0104 7F: Lost Communication With Cruise Control Module U0117 00: Lost Communication With Electrical PTO Control Module U0121 00: Lost Communication With Anti-Lock Brake System (ABS) Control Module U0122 00: Lost Communication With Vehicle Dynamics Control Module U0131 00: Lost Communication With Power Steering Control Module U0132 00: Lost Communication With Ride Level Control Module U0134 00: Lost Communication With Power Steering Control Module - Rear U0136 00: Lost Communication With Differential Control Module - Rear U0140 00: Lost Communication With Body Control Module U0141 00: Lost Communication With Body Control Module A U0151 00: Lost Communication With Restraints Control Module U0151 71: Lost Communication With Restraints Control Module Invalid Serial Data Received U0151 7F: Lost Communication With Restraints Control Module Erratic U0155 00: Lost Communication With Instrument Panel Cluster (IPC) Control Module U0156 00: Lost Communication With Information Center A (DIC) U0158 00: Lost Communication With Head Up Display U0159 00: Lost Communication With Parking Assist Control Module U0160 00: Lost Communication With Audible Alert Control Module U0164 00: Lost Communication With HVAC Control Module U0165 00: Lost Communication With HVAC Control Module - Rear U0168 00: Lost Communication With Vehicle Security Control Module U0170 00: Lost Communication With Restraints System Sensor A (PPS) U0172 00: Lost Communication With Rollover Sensor U0184 00: Lost Communication With Radio U0186 00: Lost Communication With Audio Amplifier U0291 00: Lost Communication With Television U0194 00: Lost Communication With Digital Radio Receiver (DRR) U0198 00: Lost Communication With Telematic Control Module U0199 00: Lost Communication With Door Control Module A (DDM) U0200 00: Lost Communication With Door Control Module B (PDM) U0208 00: Lost Communication With Seat Control Module A (DSM/MSM) U0209 00: Lost Communication With Seat Control Module B (HVSM) U0210 00: Lost Communication With Seat Control Module C (RHVSM) U0214 00: Lost Communication With Remote Function Actuation U0230 00: Lost Communication With Rear Gate Module U0232 00: Lost Communications With Side Object Detection (SOD) Module - Left U0233 00: Lost Communications With Side Object Detection (SOD) Module - Right U0236 00: Lost Communications With Column Locking Module (CLM) U0241 00: Lost Communication With Headlamp Control Module A U0249 00: Lost Communication With Entertainment Control Module - Rear B
DTC U1814U1814 00: Powertrain High Speed Communication Enable Circuit
DTC U2099U2099 00: High Speed Communication Enable Circuit

DIAGNOSTIC CODE INDEX

Begin the system diagnosis with Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle will provide the following information

  1. The identification of the control modules which are not communicating
  2. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check - Vehicle will identify the correct procedures to begin vehicle diagnosis. These must be performed before system DTC or symptom diagnosis.

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) 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 50, without a repeat of the malfunction.

Diagnostic Aids

  1. This DTC may be stored as a history DTC without affecting the operation of the module.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
  3. If this DTC is retrieved as both a current and history DTC, replace the module that set the DTC.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) 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-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.

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

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

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

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the control module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.

The only requirements are voltage and ground.

The module has detected that the VIN is not programmed.

  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-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) 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-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.

Conditions for Running the DTCs

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

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

  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-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.
  1. Supply voltage at the modules are in the normal operating range.
  2. The vehicle power mode requires serial data communications.

The module setting the DTC has attempted to establish communications on the 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 of 50, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Module B+U0100-U0299U0100-U0299
IgnitionU0100-U0299U0100-U0299
Module GroundU0100-U0299U0100-U0299
Accessory Wake Up Serial DataU1814U0100-U0299
High Speed GMLAN Serial Data Wake UpU2099U0100-U0299
Low Speed GMLAN Serial Data1U0100-U02991
1. Scan tool does not communicate with low speed GMLAN device

The system voltage is between 9-16 volts.

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

Specific subsystems will not function.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Use the 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 data link connector (DLC).
  3. Use «Data Link References»(ref-299166-S10811730822008092200000) to determine if the module uses high or low speed GMLAN serial data communications.
  4. Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module.
  5. This diagnostic can be used for any module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that module.

Circuit/System Testing

  1. Using the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating.
  2. Ignition OFF, disconnect the harness connector of the module that is not communicating.
  3. Ignition ON, verify that a test lamp illuminates between the serial data communication enable circuit OR the accessory wakeup serial data circuit and ground. If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  4. Test for less than 1 ohm between the module ground circuits and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  5. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits 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 fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the module.
  6. Verify that a test lamp illuminates between all ignition voltage circuits 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 fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the module.
  7. Use «Data Link References»(ref-299166-S10811730822008092200000) to verify the non-communicating module uses low speed GMLAN serial data. If the module is GMLAN high speed only, replace the module.
  8. Test for less than 1 ohm on the low speed GMLAN serial data circuit between the non-communicating module and the module that displays the DTC. If greater than the specified range, test the low speed GMLAN serial data circuit for open/high resistance.
  9. If all circuits test normal, replace the module that is not communicating.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Accessory Wake Up Serial DataU1814U0100
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode master requires serial data communication to occur.

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

  1. The modules use a default value for the missing parameters until the next ignition cycle.
  2. The modules is never signaled, therefore the specific subsystems will not function.
  3. The vehicle may not start.
  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. Short to ground may open the fuse feeding the ignition switch.
  2. Short to ground may also set multiple no communication codes for GMLAN high speed modules.
  1. Ignition OFF, disconnect the X1 harness connector at the ECM and the TCM one at a time. After each disconnect, test for current DTCs. DTC U1814 should remain current. If the DTC becomes history, replace the module disconnected when the DTC became history.
  2. Ignition OFF, disconnect the X4 harness connector at the BCM.
  3. Test for infinite resistance between the voltage circuit terminal 19 and ground. If less than the specified value, test the voltage circuit for a short to ground.
  4. If all circuits tests normal, replace the BCM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using the diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
High Speed GMLAN Serial Data Wake UpU2099, U0100-U0299 1U0100-U0299U0100-U0299 2
1 Vehicle will not start. 2 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

  1. With the ignition OFF, disconnect the X 1 harness connector at the EBCM, DSCC, and ESC module one at a time. After each disconnect, retest for current DTCs. DTC U2099 should remain current. If the DTC becomes history, replace the module disconnected before the DTC became history.
  2. Ignition OFF, disconnect the harness connector X 3 at the BCM.
  3. With the X 1 harness connector at the EBCM, DSCC, and ESC modules 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.
  4. If all circuits test normal and DTC is current, replace the BCM.

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(ref-299147-S04714420442008092200000) .
  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-299166-S01001012022008092200000)
  2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-299166-S14142603402008092200000)
  3. «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(ref-299166-S36089894062008092200000)
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) 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-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
High Speed GMLAN Serial Data (+)12*1
High Speed GMLAN Serial Data (-)12*1
Ground (DLC, terminal 5)1
Battery Positive Voltage (B+)11
* 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. No communication on any high speed GMLAN module An open in only one high speed GMLAN serial data circuit may allow degraded communication between the modules
  1. 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.
  2. Use the «Data Link References»(ref-299166-S10811730822008092200000) to identify the high speed GMLAN serial data modules.
  3. This test is used for a total high speed GMLAN communication failure. If only one module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
  4. An open in the DLC ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not communicate with the vehicle. When the scan tool is to the point of communicating with the vehicle, a message on the scan tool will indicate "no CANdi module detected" and will not communicate.
  5. The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus. The following conditions may cause a total loss of high speed GMLAN data communication: A short between high speed GMLAN (+) and high speed GMLAN (-) circuits Any of the high speed GMLAN serial data circuits shorted to ground or voltage A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
  1. Test for less than 1.0 ohm between the DLC ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for open/high resistance.
  2. Remove the terminator resistor.
  3. Test for 110-130 ohms between the terminals of the resistor. If not within the specified range, replace the resistor.
  4. Connect the terminator resistor.
  5. Ignition OFF, disconnect the harness connector X3 of the BCM.
  6. Test for less than 2 ohms of resistance in the GMLAN serial data circuit between the DLC terminal 6 and BCM terminal 16. If greater than specified, test the GMLAN serial data circuit for open/high resistance.
  7. Ignition OFF, disconnect the harness connector X4 of the BCM.
  8. Verify a test lamp illuminates between each ground circuit terminal of the BCM listed below and B+. X3 terminal 1 X3 terminal 5 X4 terminal 9 If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  9. Ignition ON, verify a test lamp illuminates between each B+ circuit terminal of the BCM listed below and ground. X4 terminal 1 X4 terminal 3 X4 terminal 4 If the test lamp does not illuminate, test the B+ circuit for an open/high resistance or short to ground.
  10. Ignition OFF, disconnect the harness connector of the vehicle communication interface module (VCIM).
  11. Test for infinite resistance between the high speed GMLAN serial data circuit of the DLC terminal 6 and ground, and terminal 14 and ground. If less than the specified range, test the serial data circuit for a short to ground.
  12. Ignition ON, test for less than 1 volt between the high speed GMLAN serial data circuit of the DLC terminal 6 and ground, and terminal 14 and ground. If greater than the specified range, test the serial data circuit for a short to voltage.
  13. Test for infinite resistance between the high speed GMLAN serial data circuits of the DLC terminal 6 and 14. If less than the specified range, test the serial data circuits for a short between them.
  14. Connect the harness connectors of the BCM and the VCIM.
  15. Disconnect the harness connector of the air suspension control module (ASCM).
  16. Attempt to communicate with the BCM. Communication should not be available. If communication is established, Test the serial data circuits between the ASCM and the terminator resistor for a short to ground, short to voltage, and a short between them. If the circuits test normal, replace the ASCM.
  17. Ignition OFF, disconnect the harness connector of the fuel pump flow control module (FPCM).
  18. Attempt to communicate with the BCM. Communication should not be available. If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the FPCM and the ASCM. If the circuits test normal, replace the FPCM.
  19. Ignition OFF, disconnect the harness connector X2 of the electronic brake control module (EBCM).
  20. Attempt to communicate with the BCM. Communication should not be available. If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the EBCM and the FPCM. If the circuits test normal, replace the EBCM.
  21. Ignition OFF, disconnect the harness connector X1 of the transfer case control module (TCCM).
  22. Attempt to communicate with the BCM. Communication should not be available. If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the TCCM and the EBCM. If the circuits test normal, replace the TCCM.
  23. Ignition OFF, disconnect the harness connector X1 of the VCIM.
  24. Attempt to communicate with the BCM. Communication should not be available. If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the VCIM and the TCCM. If the circuits test normal, replace the VCIM.
  25. Ignition OFF, connect the harness connectors of disconnected modules.
  26. Ignition OFF, disconnect the harness connector X1 of the ECM.
  27. Attempt to communicate with the BCM. Communication should not be available. If communication is established, replace the ECM.
  28. Ignition OFF, disconnect the harness connector of the transmission control module (TCM). Attempt to communicate with the BCM. Communication should not be available. If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the TCM and the ECM. If the circuits test normal, replace the TCM.
  29. Ignition OFF, disconnect the harness connector X3 of the BCM.
  30. Test for infinite resistance between the serial data circuits of BCM terminal 8 and ground, and between BCM terminal 9 and ground. If less than the specified range, test the circuit for a short to ground.
  31. Ignition ON, test for less than 1 volt between the serial data circuits of BCM terminal 8 and ground, and between BCM terminal 9 and ground. If greater than the specified range, test the circuit for a short to voltage.
  32. Test for infinite resistance between the serial data circuits of BCM terminal 8 terminal 9. If less than the specified range, test the serial data circuits for a short between them.
  33. If the circuits test normal, replace the BCM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299145-S33690120492008092200000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299145-S10820546452008092200000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Low Speed GMLAN Serial Data121
Ground (DLC, Terminal 5)1
No communication on any low speed GMLAN module No communication on a specific low speed GMLAN module
  1. Use the «Data Link References»(ref-299166-S10811730822008092200000) to identify the low speed GMLAN serial data modules.
  2. This test is used for a total low speed GMLAN communication failure. If only 1 module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
  3. An open in the low speed GMLAN serial data circuit between the splice pack and a module will only effect the specific module. This type of failure will set a loss of communication DTC for each module effected, and the other modules will still communicate.
  4. An open in the DLC ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not communicate with the vehicle. When the scan tool is to the point of communicating with the vehicle, a message on the scan tool will indicate "no CANdi module detected" and will not communicate.
  5. An open between the DLC and JX 205 will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
  6. The engine will not start when there is a total malfunction of the low speed GMLAN serial data circuit. The following conditions may cause a total loss of low speed GMLAN data communication: The low speed GMLAN serial data circuit shorted to ground or voltage. A module internal malfunction that causes a short to voltage or ground on the low speed GMLAN circuit.
  1. Test for less than 1 ohm between the DLC ground circuit terminal 5 and ground. If greater than The specified range, test the ground circuit for open/high resistance.
  2. Ignition OFF, disconnect the JX 205 harness connector at the splice pack.
  3. Ignition ON, with a scan tool, attempt to communicate with the instrument panel cluster (IPC). Communication should be available. If no communication, disconnect the modules still connected to the DLC one at a time, starting with the furthest from the DLC and attempt to communicate after each disconnect. When communication occurs, test the serial data circuit for a short to ground and a short to voltage between the last module disconnected and the previous module disconnected. If the circuit tests normal, replace the last module disconnected. If no communication is possible, test the serial data circuit for a short to ground, a short to voltage or an open/high resistance between the last module disconnected and the DLC. If the circuit tests normal, replace the last module disconnected.
  4. Install a 3-amp fused jumper wire to JX 205 terminal A, harness side.
  5. With IPC communications established, use the other end of the jumper wire to connect all other terminals, harness side, one at a time and verify that low speed communication remains available to the IPC. If low speed communication is interrupted after connecting an individual module at JX 205, test the serial data circuit between JX 205 and the last module connected for a short to voltage and short to ground. If the circuit tests normal, replace the module that caused no communication.

Circuit Description

The communication among control modules is performed through the high speed GMLAN serial data circuits and the low speed GMLAN serial data circuit. The modules that need real time communication are attached to the High Speed GMLAN network. The body control module (BCM) is the gateway between the high and low speed networks. Refer to Body Control System Description and Operation for more information about the gateway.

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.

GMLAN High Speed Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data circuit. The serial data is transmitted on 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.

GMLAN Low Speed Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the low speed GMLAN serial data circuit. The serial data is transmitted over a single wire to the appropriate control modules. Under normal vehicle operating conditions, the speed of the buss is 33.33 Kb/s. This protocol produces a simple pulse train sent out over the GMLAN low speed serial data bus. When a module pulls the buss high, 5 volts, this creates a logic state of 0 on the buss. When the buss is pulled low, 0 volts, it is translated as a logic state of 1. To wake the control modules connected to the GMLAN low speed serial data buss, a wake up signal is sent out over the buss. Modules connected to the GMLAN low speed buss can be part of a virtual network as described in GMLAN High Speed Circuit Description above. The modules on the GMLAN low speed serial data buss are connected to the buss 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)

More articles — Data Communications