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Data Communication System: Diagnosis Chevrolet HHR I

Communication Devices ~5243 words

DIAGNOSTIC CODE INDEX

DTCDescription
DTC B1000B1000 00: Electronic Control Unit (ECU) Performance - No Additional Information B1000 31: Electronic Control Unit (ECU) Performance - General Checksum Error B1000 57: Electronic Control Unit (ECU) Performance - Expected Reaction After Event Did Not Occur
DTC B1001B1001 00: Option Configuration Error B1001 45: Option Configuration Error Variant Not Programmed B1001 46: Option Configuration Error B1001 4B: Option Configuration Error Calibration Not Learned
DTC B1004B1004: Keep Alive Memory (KAM) Reset
DTC B1009B1009: EEPROM Checksum Mismatch
DTC C0550C0550 00: EEPROM Checksum Mismatch C0550 39: EEPROM Checksum Mismatch
DTC U0001U0001 00: High Speed CAN Communication Bus
DTC U0073Controller Area Network (CAN) Bus Communication
DTC U1300, U1301, or U1305U1300: Class 2 Data Link Low U1301: Class 2 Data Link High U1305: Class 2 Data Link High or Low
DTC U2103U2103 00: Fewer Controllers On Than Programmed
DTC U2105-U2199U2105 00: Lost Communication With Engine Control System U2106 00: Lost Communication With Transmission Control System U2107 00: Lost Communication With Body Control System U2108 00: Lost Communication With ABS/TCS Control System U2109 00: Lost Communication With Powertrain Control System U2110 00: Lost Communication With Chassis Multiple Control System U2111 00: Lost Communication With Steering Control System U2112 00: Lost Communication With Electronic Suspension Control (ESC) U2113 00: Lost Communication With Sensing and Diagnostic Module (SDM) U2114 00: Lost Communication With PPS or CPS U2115 00: Lost Communication With (Restraints Control System) U2116 00: Lost Communication With Instrument Panel Cluster (IPC) U2117 00: Lost Communication With Driver Information Center (DIC) U2118 00: Lost Communication With Head Up Display (HUD) U2119 00: Lost Communication With Daytime Running Lamps (DRL) System U2120 00: Lost Communication With Automatic Headlamp Leveling Device (AHLD) U2121 00: Lost Communication With Radio Display U2122 00: Lost Communication With Radio U2123 00: Lost Communication With Compact Disc Changer (CDX) U2124 00: Lost Communication With Audio Amplifier U2125 00: Lost Communication With Telematic Unit U2126 00: Lost Communication With (Mobile Communications Control System) U2127 00: Lost Communication With Front HVAC U2128 00: Lost Communication With Rear HVAC U2129 00: Lost Communication With Remote Function Actuator (RFA) U2130 00: Lost Communication With Driver Door Module (DDM) U2131 00: Lost Communication With Driver Seat Module (DSM) U2132 00: Lost Communication With Passenger Door Module (PDM) U2133 00: Lost Communication With Passenger Seat Module (PSM) U2134 00: Lost Communication With Rear Door Module (RDM) U2135 00: Lost Communication With Rear Integration Module (RIM) U2136 00: Lost Communication With Memory Mirror Module (MMM) U2137 00: Lost Communication With Vehicle Theft Deterrent (VTD) U2138 00: Lost Communication With Column Locking Module (CLM) U2139 00: Lost Communication With Column Integration Module (CIM) U2140 00: Lost Communication With Underhood Electrical Center (UEC) U2141 00: Lost Communication With Rear Electrical Center (REC) U2142 00: Lost Communication With Yaw Rate Sensor (YRS) U2143 00: Lost Communication With Steering Angle Sensor (SAS) U2144 00: Lost Communication With Distance Sensing Cruise Control Module U2145 00: Lost Communication With Parking Assistance System (PAS) U2146 00: Lost Communication With Shift Lever Module (SLM) U2147 00: Lost Communication With Auxiliary Heater System (AHS) U2148 00: Lost Communication With Sun Roof Module (SRM) U2149 00: Lost Communication With Tire Pressure Monitor (TPM) System U2150 00: Navigation Electronic Control Unit (ECU) Gateway Communications U2151 00: Navigation Electronic Control Unit (ECU) Communications U2152 00: Navigation Bus Request Line Circuit Low U2153 00: Navigation Electronic Control Unit (ECU) - VICS Communication Circuit U2160 00: Lost Communication With Steering Control System Sensor U2161 00: Lost Communication With Dash Integration Module (DIM) U2162 00: Lost Communication With Instrument Panel integration Module (IPM) U2163 00: Lost Communication With Left Rear Door Module (LRDM) U2164 00: Lost Communication With Right Rear Door Module (RRDM) U2165 00: Lost Communication With Driver Door Switch (DDS) U2166 00: Lost Communication With Driver Position Module (DPM) U2167 00: Lost Communication With Remote Control Door Lock Receiver U2168 00: Lost Communication With Side Object Detection (SOD) Module - Left U2169 00: Lost Communication With Side Object Detection (SOD) Module - Right U2170 00: Lost Communication With Four Wheel Drive (4WD) Clutch U2171 00: Lost Communication With Rear Seat Entertainment (RSE) U2172 00: Lost Communication With Digital Radio Receiver U2173 00: Lost Communication With Passive Entry and Passive Start System U2174 00: Lost Communication With Parking Heater System U2175 00: Lost Communication With Special Vehicle Module U2176 00: Lost Communication With Power Take Off (PTO) Control Module U2177 00: Lost Communication With Cruise Control Module U2178 00: Lost Communication With Trailer Interface Module U2179 00: Lost Communication With Television Module U2180 00: Lost Communication With Folding Top Control Module U2181 00: Lost Communication With Moveable Roof Module

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Data Communications

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-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

The control module has detected an internal malfunction.

Action Taken When the DTC Sets

The control 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 in all of the modules except the sensing and diagnostic module (SDM), when the ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
  3. If the code is set in the SDM it will never clear and the Air Bag indicator will remain illuminated.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) 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-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.

The control module microprocessor must be active/awake.

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

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

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) 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-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) 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.

If equipped, the following module specific actions may occur

  1. The antilock brake system (ABS) indicator turns ON.
  2. The BRAKE warning indicator turns ON.
  3. The electronic brake control module (EBCM) disables the ABS/dynamic rear proportion (DRP)/traction control system (TCS).
  4. The driver information center (DIC) displays the power steering warning message No Steering Assist.
  5. The TCS indicator turns ON.
  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-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.

Circuit Description

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

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

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

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

Diagnostic Aids

  1. This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with GMLAN Device. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-299572-S39797886592008092400000) .
  2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with GMLAN Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-299572-S39797886592008092400000) .

The GMLAN serial data circuits are controller area network (CAN) high and/or low speed 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. There are two different types of GMLAN serial data circuits, the High speed 2-wire circuit and Low speed single wire circuit. Refer to Data Link References for the complete description of the buses used on this vehicle. The GMLAN serial data circuits also communicate directly to the data link connector (DLC). 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 U0073 will result.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC U0073 Controller Area Network (CAN) Bus Communication

Conditions for Running the DTCs

  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, 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 and/or Low Speed GMLAN Device. Refer to «Control Module References»(ref-299597-S40606836452008092400000) for the correct procedure for the specific module(s) and the busses they use to communicate.
  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 and/or Low Speed GMLAN Device procedure in order to isolate an intermittent condition. Refer to «Control Module References»(ref-299597-S40606836452008092400000) for the correct procedure for the specific modules.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to Voltage
Class 2 Serial DataU13001U1301
1. Some modules will set DTC U1305 if they are not capable of distinguishing between a short to battery voltage or ground.

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects high or low voltage on the class 2 serial data circuit for approximately 3 seconds, the setting of all other class 2 serial communication DTCs is inhibited and a DTC will set.

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

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. These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom «Scan Tool Does Not Communicate with Class 2 Device»(ref-299572-S22147572092008092400000) .
  2. An intermittent condition is likely to be caused by a short on the class 2 serial data circuit.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) 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, «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(ref-299572-S17036174012008092400000) .
  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 Low Speed GMLAN Device»(ref-299572-S17036174012008092400000) procedure in order to isolate an intermittent condition.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using the diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Low Speed GMLAN Serial Data1U2105-U21991
Battery Positive Voltage CircuitsU2105-U2199U2105-U2199
Ignition Voltage CircuitsU2105-U2199U2105-U2199
Module Ground CircuitsU2105-U2199U2105-U2199
Accessory Wake Up Serial DataU1814U2105-U2199
High Speed GMLAN Serial Data Wake UpU2099U2105-U2199
1. Scan tool does not communicate with low speed GMLAN device
  1. The system voltage is between 9-16 volts.
  2. The vehicle power mode requires serial data communication to occur.

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

The module uses a default value for the missing parameters.

  1. A current DTC clears when the malfunction is no longer present.
  2. A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
  1. 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-299572-S02847788732008092400000) 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

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

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(ref-299596-S12390038412008092400000) .
  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-299572-S13978516522008092400000)
  2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-299572-S39797886592008092400000)
  3. «Scan Tool Does Not Communicate with Low Speed GMLAN Device»(ref-299572-S17036174012008092400000)
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Class 2 Serial Data111
Ground (DLC, terminal 5)1
1 A short voltage, short to ground, or an open between the data link connector (DLC) and the PCM, or an open between the DLC terminal 5 and ground will only effect the communication with the scan tool. The PCM will still communicate on HS GMLAN.

The powertrain control module (PCM) is connected to the class 2 serial data circuit. The class 2 serial data circuit is used for diagnostic purposes only in this vehicle. Connecting a scan tool to the data link connector (DLC) allows communication with the PCM for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

  1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground. If greater than 1.0 ohm, test the ground circuit for open/high resistance.
  2. Ignition OFF, disconnect the X1 harness connector at the PCM.
  3. Test for less then 5 ohms between the class 2 serial data circuit terminal 16 and ground. If greater then the specified range, test the serial data circuit for a short to open/high resistance.
  4. Ignition ON, test for less then 1 volt between the serial data circuit terminal 16 and ground. If greater then the specified range, test the serial data circuit for a short to voltage.
  5. If all circuits test normal, replace the PCM.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) 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-299572-S02847788732008092400000) 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 and 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 ground circuit terminal 5 of the DLC and ground. If greater than the specified range, test the ground circuit for open/high resistance.
  2. Ignition OFF, disconnect the X2 harness connector at the BCM.
  3. Test for less than 2 ohms on the serial data circuit between terminal 6 of the DLC and terminal 1 of the BCM. If greater than the specified range, test the serial data circuit for open/high resistance.
  4. Ignition OFF, disconnect the X4 harness connector at the BCM.
  5. Test for less than 1 ohm between ground circuit terminal E12 and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Ignition OFF, disconnect the X3 harness connector at the BCM.
  7. Ignition ON, verify a test lamp illuminates between each B+ circuit terminal D12 of the BCM and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance or short to ground.
  8. Ignition ON, test for less than 1 volt between the serial data circuit terminal 6 of the DLC and ground, and terminal 14 of the DLC and ground. If greater than the specified range, test the serial data circuit for a short to voltage.
  9. Test for infinite resistance between the serial data circuit terminal 6 of the DLC and ground, and terminal 14 of the DLC and ground. If less than the specified value, test the serial data circuit for a short to ground.
  10. Disconnect the X2 harness connector at the electronic power steering control module (EPS).
  11. Test for infinite resistance between the serial data circuits terminal 6 and terminal 14 of the DLC. If less than the specified value, test the serial data circuits for a short between them.
  12. Connect the X2 X3 and X4 harness connectors at the BCM and the X2 harness connector at the EPS.
  13. Disconnect the appropriate harness connector at the ECM. RPO L61/LE5 - X1 RPO LNF - X2
  14. Attempt to communicate with the vehicle control interface module (VCIM). Communication should not be available. If communication is available, replace the ECM.
  15. Ignition OFF, disconnect the harness connector at the TCM.
  16. Attempt to communicate with the VCIM. Communication should not be available. If communication is available, test the following 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. RPO L61/LE5 - 43 RPO L61/LE5 - 44 RPO L61/LE5 - 43 and 44 RPO LNF - 33 RPO LNF - 53 RPO LNF - 33 and 53
  17. Ignition OFF, disconnect the harness connector at the EBCM.
  18. Attempt to communicate with the VCIM. Communication should not be available. If communication is available, test the following serial data circuits for a short between the circuits, short to voltage, or a short to ground between the EBCM and the TCM. If the circuits test normal, replace the EBCM. RPO JM4 - 21 RPO JM4 23 RPO JM4 21 and 23 RPO JL4 14 RPO JL4 11 RPO JL4 14 and 11
  19. Ignition OFF, disconnect the X3 harness connector at the VCIM.
  20. Attempt to communicate with the EPS. Communication should not be available. If communication is available, test the following serial data circuits for a short between the circuits, short to voltage, or a short to ground between the VCIM and the TCM. If the circuits test normal, replace the VCIM. 9 8
  21. Ignition OFF, disconnect the X2 harness connector at the BCM. Attempt to communicate with the EPS. Communication should not be available. If communication is available, test the following serial data circuits for a short between the circuits, short to voltage, or a short to ground between the BCM and the VCIM. If the circuits test normal, replace the BCM. 2 20
  22. Ignition OFF, disconnect the X2 harness connector at the EPS.
  23. Ignition ON, test for less than 1 volt between the following serial data circuits of EPS and ground. 4 5 If greater than the specified range, test the circuit for a short to voltage.
  24. Test for infinite resistance between the following serial data circuits of EPS and ground. 4 5 If less than the specified value, test the circuit for a short to ground.
  25. Test for infinite resistance between the serial data circuits terminal 4 terminal 5 of the EPS. If less than the specified Value, test the serial data circuits for a short between them.
  26. If the circuits test normal, replace the EPS.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-299594-S04632865592008092400000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-299594-S36605711112008092400000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-299594-S36190634062008092400000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Low speed GMLAN serial data12 11
1 An open between the data link connector (DLC) and the splice pack will only effect the communication with the scan tool. The vehicle modules will still communicate. 1. No communication on any low speed GMLAN module 2. No communication on one or a specific group of low speed GMLAN modules
  1. Use the «Data Link References»(ref-299572-S02847788732008092400000) 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 U2105-U2199»(ref-299572-S13030638542008092400000) for diagnostics.
  3. An open in the low speed GMLAN serial data circuit between the splice pack and a module(s) will only effect the specific module(s). This type of failure will set a loss of communication DTC for each module effected, and the other modules will still communicate. Depending on which module is effected, the vehicle may not start.
  4. An open between the data link connector (DLC) and the splice pack will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
  5. Use the DMM MIN/MAX function to capture/locate intermittent conditions.
  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. Ignition OFF, disconnect the harness connector at the low speed splice pack.
  2. Ignition ON, test for less than 1.0 volt between the low speed GMLAN serial data circuit of the DLC and ground. If greater than 1.0 volt, repair the serial data circuit for a short to voltage.
  3. Test for infinite resistance between the serial data circuit of the DLC and ground. If less than infinite resistance, repair the serial data circuit for a short to ground.
  4. Test for less than 1.0 ohm of resistance in the serial data circuit between the DLC and the splice pack. If greater than 1.0 ohm, repair the serial data circuit for an open/high resistance.
  5. Install a 3-amp fused jumper wire between pin A and pin M of the splice pack. Install another 3-amp fused jumper wire to pin M.
  6. Using the extra jumper wire from pin M attempt to establish communications with any other module connected to the splice pack. At least one module should be able to communicate. If communications can't be established with any module, test the serial data circuit of the BCM for a short to voltage, short to ground or open/high resistance. If the circuit tests normal, replace the BCM.
  7. Using the extra jumper wire at pin M, continue testing each serial data circuit at the splice pack for communications. All modules should be able to communicate. If there is only one module connected, test the serial data circuit for a short to voltage or a short to ground. If the circuit tests normal, replace the faulty module. If there are multiple modules, test each serial data circuit for a short to voltage or a short to ground, with the modules disconnected. If the circuit tests normal, install each module one at a time starting with the closest module to the splice pack until communications stop. Replace the faulty module.
  8. If all circuits test normal, test or replace the splice pack.

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

The powertrain control module (PCM) on this vehicle, uses a class 2 serial data buss. The class 2 buss is only used for diagnostics and the service programming system (SPS). During normal vehicle operations, there is no communications over the class 2 serial data buss. Normal vehicle operational messaging for the PCM is sent over the PCMs GMLAN high speed serial data buss.

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

GMLAN Low Speed Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the low speed GMLAN serial data circuit. The serial data is transmitted over a single wire to the appropriate control modules. The transmission speed for GMLAN low speed is up to 83.33 Kb/s. Under normal vehicle operating conditions, the speed of the buss is 33.33 Kb/s. This protocol produces a simple pules train sent out over the GMLAN low speed serial data bus. When a module pulls the buss high, 5 volts, this creates a dominant logic state or 0 on the buss. When the buss is pulled low 0 volts, it is translated as a recessive logic state or 1. To wake the control modules connected to the GMLAN low speed serial data buss, a high voltage wake up pulse is sent out over the buss, the voltage level of the pules is +10 volts. Modules connected to the GMLAN low speed buss can be part of a virtual network as described in the previous paragraph. The modules on the GMLAN low speed serial data buss are connected to the buss in a parallel configuration.

Class 2 Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data circuit. Class 2 serial data is transmitted on a single wire at an average of 10.4 Kbps. The bus is active at 7 volts nominal and inactive at ground potential. When the ignition switch is in RUN, and a scan tool is connected to the DLC, the powertrain control module (PCM) will start communicating diagnostic information over the class 2 serial data circuit.

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