Computer/Integrating Systems Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs. IMPORTANT: Twisted-pair wires provide an effective shield that helps protect sensitive electronic components from electrical interference. In order to prevent electrical interference from degrading the performance of the connected components, you must maintain the proper specification when making any repairs to the twisted-pair wires shown : The wires must be twisted a minimum of 9 turns per 31 cm (12 in) as measured anywhere along the length of the wires. The outside diameter of the twisted wires must not exceed 6.0 mm (0.25 in)
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Scheme 11
| Callout | Component Name |
|---|---|
| 1 | Turn Signal/Hazard Flasher Module |
| 2 | Instrument Panel Harness |
| 3 | Data Link Connector (DLC) |
| 4 | Splice Pack SP205 |
Scheme 12
| Callout | Component Name |
|---|---|
| 1 | Body Control Module (BCM) |
| 2 | Fuse Block - Rear |
| 3 | Body Control Module Connectors C1 and C2 |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: A DTC U1001 - U1254 Lost Communications with XXX with a history status may indicate the cause of U1000.
- 3: The modules not communicating are the likely cause of U1000. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
- 7: The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 Lost Communications with XXX for those modules that it was monitoring.
- 10: The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
- 13: If all modules are communicating, the module which set U1000 may have done so due to some other condition.
- 15: The module which set U1000 is the likely cause of the malfunction.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. Record the DTCs set in by each module. If using a Tech 2, use the class 2 DTC Check feature to determine which modules have DTCs set. Did you record any DTCs in the range of U1001-U1254 with a history status? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 |
| 3 | Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the class 2 Message Monitor feature. Record all of the modules communicating on the class 2 serial data circuit. Compare the list of modules which are communicating to the list given in Circuit Description. Does any module on the class 2 serial data circuit not communicate? | Go to Step 4 | Go to Step 13 |
| 4 | Test the following circuits of the module that is not communicating for an open or short to ground: The battery positive voltage supply circuits The switched battery positive supply circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits Refer to the following: Control Module References for applicable schematics Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 9 | Go to Step 5 |
| 5 | Turn OFF the ignition. Test the ground circuits of the module that is not communicating for an open. Refer to the following: Control Module References for applicable schematics Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
| 6 | IMPORTANT: Inspect all connectors in the serial data communications circuit. Refer to the following: Data Link Connector (DLC) Schematics Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Turn OFF the ignition. Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to the following: Data Link Connector (DLC) Schematics Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
| 7 | Inspect the harness connector of the module that is not communicating for poor connections and terminal tension at the following circuits: The battery positive voltage input circuits The switched battery positive voltage supply The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The ground circuits The class 2 serial data circuits Refer to the following: Control Module References for applicable schematics Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
| 8 | Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 11 | |
| 9 | Install a scan tool. Turn ON the ignition, with the engine OFF. Select the Display DTCs function for the module which was not communicating. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 10 |
| 10 | Use the scan tool in order to clear the DTCs. Did you complete the action? | Go to Step 11 | |
| 11 | Select the Display DTCs function for the modules which had U1000 set as a current DTC. Does the scan tool display DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 12 |
| 12 | Use the scan tool in order to clear the DTCs. Did you complete the action? | System OK | |
| 13 | Did you record any other DTCs for the modules which had U1000 set as a current DTC? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 14 |
| 14 | Install a scan tool. Turn ON the ignition, with the engine OFF. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for at least 5 seconds. Turn ON the ignition, with the engine OFF. Select the Display DTCs function. Does the scan tool display U1000 set as a current DTC? | Go to Step 15 | Go to Diagnostic Aids |
| 15 | Replace the module which had U1000 set as a current DTC. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | System OK | |
| IMPORTANT |
|---|
| Inspect all connectors in the serial data communications circuit. Refer to the following: Data Link Connector (DLC) Schematics Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems |
DTC U1000
The number below refers to the step number on the diagnostic table.
- 7: The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | IMPORTANT: Use the control module ID number list in order to determine which module is not communicating. Test the following circuits of the module that is not communicating for an open or a short to ground: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage circuits Refer to the following: Control Module References for applicable schematics Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 7 | Go to Step 3 |
| 3 | Turn OFF the ignition. Test the ground circuits of the module that is not communicating for an open. Refer to the following: Control Module References for applicable schematics Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 7 | Go to Step 4 |
| 4 | Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 5 |
| 5 | Inspect the harness connectors of the module that is not communicating for poor connections and terminal tension at the following circuits: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage supply circuits The ground circuits The class 2 serial data circuits Refer to the following: Control Module References for applicable schematics Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 7 | Go to Step 6 |
| 6 | Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 7 | |
| 7 | Install a scan tool. Turn ON the ignition with the engine OFF. Select the Display DTCs function for the module which was not communicating. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 8 |
| 8 | Select the Display DTCs function for the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 9 |
| 9 | Use the scan tool in order to clear the DTCs. Continue diagnosing or clearing the DTCs until all the modules have been diagnosed and all the DTCs have been cleared. Did you complete the action? | System OK | |
| IMPORTANT |
|---|
| Use the control module ID number list in order to determine which module is not communicating. |
DTC U1001-U1254
The numbers below refer to the step numbers on the diagnostic table.
- 6: The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the splice pack SP306 serial data circuits.
- 14: This test isolates the splice pack SP205 serial data circuits.
- 20: If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
- 21: The communication malfunction may have prevented diagnosis of the customer complaint.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Did you record U1300 or U1301, as current? | Go to Step 4 | Go to Step 3 |
| 3 | IMPORTANT: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems: Testing for Intermittent Conditions and Poor Connections Circuit Testing Connector Repairs Wiring Repairs Did you find and correct the condition? | Go to Step 22 | |
| 4 | Turn OFF the ignition. Disconnect the engine control module (ECM). Turn ON the ignition. Attempt to communicate with the body control module (BCM). Does the scan tool communicate with BCM? | Go to Step 18 | Go to Step 5 |
| 5 | Turn OFF the ignition. Reconnect the ECM. Disconnect the splice pack SP306. Turn ON the ignition, with the engine OFF. Retrieve the DTCs from the ECM. Did you record U1300 or U1301, as current? | Go to Step 8 | Go to Step 6 |
| 6 | Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP306 until the concern is located: Turn OFF the ignition. Using the correct terminal adapter, connect a jumper wire to the splice pack SP205 terminal of the splice pack SP306. Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP306. Turn ON the ignition, with the engine OFF. Retrieve the DTCs from the ECM. Did you record U1300 or U1301, as current? | Go to Step 7 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 7 | Turn OFF the ignition. Disconnect the module that caused the DTC to be set. Test the class 2 serial data circuit between the splice pack SP306 and the respective module for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 18 |
| 8 | Turn OFF the ignition. Disconnect the splice pack SP205. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current? | Go to Step 9 | Go to Step 12 |
| 9 | Turn OFF the ignition. Disconnect the theft deterrent control module (VTD), if equipped, or disconnect the BCM, if not equipped with VTD. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current? | Go to Step 11 | Go to Step 10 |
| 10 | Turn OFF the ignition. Test the class 2 serial data circuit between VTD, if equipped, or BCM if not equipped with VTD, and splice pack SP205 for a short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 16 |
| 11 | Turn OFF the ignition. Disconnect the ECM. Test the class 2 serial data circuit between the ECM and VTD, if equipped, or BCM if not equipped with VTD, for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Test the class 2 serial data circuit between the ECM and splice pack SP306 for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 16 |
| 12 | Turn OFF the ignition. Using the correct terminal adapter, connect a jumper wire to the ECM terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the splice pack SP306 terminal of the splice pack SP205. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current? | Go to Step 13 | Go to Step 14 |
| 13 | Turn OFF the ignition. Repair the short to ground or short to voltage in the class 2 serial data circuit between the splice pack SP205 and the splice pack SP306. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | |
| 14 | Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP205 until the concern is located: Turn OFF the ignition. Leave the jumper wire connected to the ECM terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP205. Turn ON the ignition, with the engine OFF. Retrieve DTCs from ECM. Did you record U1300 or U1301, as current? | Go to Step 15 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 15 | Turn OFF the ignition. Disconnect the module that caused the DTC to be set. Test the class 2 serial data circuit between the splice pack SP205 and the respective module for a short to ground or a short to voltage. Turn ON the ignition, with the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 18 |
| 16 | Inspect for poor connections at the class 2 serial data circuit of the VTD, if equipped, or BCM, if not equipped with VTD. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 17 |
| 17 | Replace the VTD, if equipped, or BCM, if not equipped with VTD. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 20 | |
| 18 | Inspect for poor connections at the class 2 serial data circuit of the last disconnected module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 20 | Go to Step 19 |
| 19 | Replace the last disconnected module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 20 | |
| 20 | Reconnect all of the disconnected modules and splice packs. Install a scan tool. Turn ON the ignition, with the engine OFF. Retrieve the DTCs. Did you record any DTCs which begin with a "U" and with a current status? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 21 |
| 21 | Did you record any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 22 |
| 22 | Use the scan tool in order to clear the DTCs. Did you complete the action? | System OK | |
| IMPORTANT |
|---|
| Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. |
DTC U1300, U1301, or U1305 (5.3L)
The number below refers to the step number on the diagnostic table.
- 4: If the battery positive voltage and ground circuits of the DLC are functioning properly, the malfunction must be due to the scan tool.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Computer/Integrating Systems Connector End Views | |||
| 1 | Test the battery positive voltage circuit of the data link connector (DLC) for an open or a short to ground. Refer to the following procedures in Wiring Systems: Circuit Testing Wiring Repairs Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 2 |
| 2 | Test the ground circuits of the DLC for an open or high resistance. Refer to the following procedures in Wiring Systems: Circuit Testing Wiring Repairs Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 3 |
| 3 | Inspect for poor connections and terminal tension at the DLC. Refer to the following procedures in Wiring Systems: Testing for Intermittent Conditions and Poor Connections Connector Repairs Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 4 |
| 4 | The scan tool may be malfunctioning. Refer to the scan tool user guide. Did you obtain a properly operating scan tool? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
Scan Tool Does Not Power Up
The numbers below refer to the step numbers on the diagnostic table.
- 2: A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on class 2 serial data bus: The body control module (BCM) The communication interface module (OnStar®), w/UE1 The digital radio receiver (DRR), w/U2K The driver door module (DDM) The driver seat module (DSM), w/AAB The DVD player The electronic brake control module (EBCM) The endgate module (EGM), for XUV The HVAC control module The HVAC control module - rear auxiliary The inflatable restraint sensing and diagnostic module (SDM) The instrument panel cluster (IPC) The liftgate control module (LGM), except XUV The passenger door module (PDM) The power roof module (PRM), for XUV The powertrain control module (PCM) The radio The transfer case shift control module (TCSCM), w/4WD
- 3: The following DTCs may be retrieved with a history status, but are not the cause of the present condition. U1300 U1301 U1305
- 6: A state of health (SOH) DTC with a history status may be present along with a U1000 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
- 7: Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
- 10: A poor connection at DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.
- 11: An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
- 12: The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the BCM and the PCM class 2 serial data circuits.
- 13: This test isolates the BCM class 2 serial data circuits.
- 16: The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the splice pack SP306 serial data circuits.
- 21: This test isolates the rest of the splice pack SP205 serial data circuits.
- 25: If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
- 26: The communication malfunction may have prevented diagnosis of the customer complaint.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems IMPORTANT: This test is used for vehicles with Passlock System, as vehicle theft deterrent. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature. Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 3 | Go to Step 8 |
| 3 | Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all of the displayed DTCs, the DTC status, and the module which set the DTC. Did you record any DTCs in the range of U1000 to U1305? | Go to Step 4 | Go to Step 7 |
| 4 | Are the history DTCs U1300, U1301, or U1305 retrieved from any module? | Go to Step 5 | Go to Step 6 |
| 5 | IMPORTANT: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems: Testing for Intermittent Conditions and Poor Connections Circuit Testing Connector Repairs Wiring Repairs Did you find and correct the condition? | Go to Step 25 | Go to Step 6 |
| 6 | Is U1000 the only DTC displayed in the previously specified range? | Go to DTC U1000 | Go to DTC U1001-U1254 |
| 7 | Diagnose the non-communicating module by using the DTC U1001-U1254 procedure for the module which is not communicating. Refer to DTC U1001-U1254 . Did you complete the action? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 8 | Turn OFF the ignition. Disconnect the scan tool from the data link connector (DLC). Inspect for poor connections at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 9 |
| 9 | Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 10 |
| 10 | Disconnect the splice pack SP205. Inspect for poor connections at the splice pack SP205. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 11 |
| 11 | Test the class 2 serial data circuit between the DLC and the splice pack SP205 for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 12 |
| 12 | Using the correct terminal adapter, connect a jumper wire to the DLC terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the body control module (BCM) terminal of the splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 16 | Go to Step 13 |
| 13 | Turn OFF the ignition. Disconnect the powertrain control module (PCM). Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 14 | Go to Step 15 |
| 14 | Turn OFF the ignition. Test the class 2 serial data circuit between the splice pack SP205 and the PCM for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 |
| 15 | Turn OFF the ignition. Disconnect the BCM. Test both class 2 serial data circuits of the BCM for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 |
| 16 | Leave the jumper wire connected to the DLC terminal and to the BCM terminal of the splice pack SP205. Connect another jumper wire from the jumper wire connected to the DLC terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the splice pack SP306 terminal of the splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 21 | Go to Step 17 |
| 17 | Disconnect the splice pack SP306. Inspect for poor connections at the splice pack SP306. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 19 | Go to Step 18 |
| 18 | Repair the class 2 serial data circuit for a short to ground or a short to voltage between the splice pack SP205 and the splice pack SP306. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | |
| 19 | Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP306 until the concern is located: Connect another jumper wire to the splice pack SP205 terminal of the splice pack SP306. Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP306. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 25 | Go to Step 20 |
| 20 | Turn OFF the ignition. Disconnect the module that caused the no communication condition. Test the class 2 serial data circuit between the splice pack SP306 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 |
| 21 | Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP205 until the concern is located: Disconnect the jumper wire from the splice pack SP306 terminal of the splice pack SP205. Connect the jumper wire, using correct terminal adapter, to the terminal of the rest of modules connected to splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 25 | Go to Step 22 |
| 22 | Turn OFF the ignition. Disconnect the module that caused the no communication condition. Test the class 2 serial data circuit between the splice pack SP205 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 |
| 23 | Inspect for poor connections at the class 2 serial data circuit of the module that induced the failure. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 24 |
| 24 | Replace the module that induced the failure. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 25 | |
| 25 | Reconnect all of the disconnected modules. Reconnect any other disconnected connectors. Install a scan tool. Turn ON the ignition, leaving the engine OFF. Wait for 10 seconds. The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF the scan tool prior to performing this test. Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all of the displayed DTCs and the DTC status. Did you record any DTCs which begin with a "U" and with a current status? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 26 |
| 26 | Did you record any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 27 |
| 27 | Use the scan tool in order to clear the history DTCs. Did you complete the action? | System OK | |
| IMPORTANT |
|---|
| This test is used for vehicles with Passlock System, as vehicle theft deterrent. |
| IMPORTANT |
|---|
| Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. |
Scan Tool Does Not Communicate with Class 2 Device (4.2L w/o Immobilizer)
The numbers below refer to the step numbers on the diagnostic table.
- 2: A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on class 2 serial data bus: The body control module (BCM) The communication interface module (OnStar®), w/UE1 The digital radio receiver (DRR), w/U2K The driver door module (DDM) The driver seat module (DSM), w/AAB The DVD player The electronic brake control module (EBCM) The endgate module (EGM), for XUV The HVAC control module The HVAC control module - rear auxiliary The inflatable restraint sensing and diagnostic module (SDM) The instrument panel cluster (IPC) The liftgate control module (LGM), except XUV The passenger door module (PDM) The power roof module (PRM), for XUV The powertrain control module (PCM) The radio The transfer case shift control module (TCSCM), w/4WD The theft deterrent control module (VTD)
- 3: The following DTCs may be retrieved with a history status, but are not the cause of the present condition. U1300 U1301 U1305
- 6: A state of health (SOH) DTC with a history status may be present along with a U1000 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
- 7: Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
- 10: A poor connection at the DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.
- 11: This step may eliminate the loop created by the PCM and VTD from failure cause.
- 12: An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
- 14: The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wire for a short, make sure there is not a module connected to the wire being tested. This test isolates the BCM class 2 serial data circuits.
- 16: This test isolates the PCM class 2 serial data circuits.
- 18: The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the splice pack SP306 serial data circuits.
- 23: This test isolates the rest of the splice pack SP205 serial data circuits.
- 27: If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
- 28: The communication malfunction may have prevented diagnosis of the customer complaint.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems IMPORTANT: This test is used for vehicles with Passkey III+ System (PK3+), as vehicle theft deterrent. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature. Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 3 | Go to Step 8 |
| 3 | Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all of the displayed DTCs, the DTC status, and the module which set the DTC. Did you record any DTCs in the range of U1000-U1305? | Go to Step 4 | Go to Step 7 |
| 4 | Are the history DTCs U1300, U1301 or U1305 retrieved from any module? | Go to Step 5 | Go to Step 6 |
| 5 | IMPORTANT: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems: Testing for Intermittent Conditions and Poor Connections Circuit Testing Connector Repairs Wiring Repairs Did you find and correct the condition? | Go to Step 25 | Go to Step 6 |
| 6 | Is U1000 the only DTC displayed in the previously specified range? | Go to DTC U1000 | Go to DTC U1001-U1254 |
| 7 | Diagnose the non-communicating module by using the DTC U1001-U1254 procedure for the module which is not communicating. Refer to DTC U1001-U1254 . Did you complete the action? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 8 | Turn OFF the ignition. Disconnect the scan tool from the data link connector (DLC). Inspect for poor connections at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 9 |
| 9 | Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 10 |
| 10 | Disconnect the splice pack SP205. Inspect for poor connections at the splice pack SP205. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 11 |
| 11 | Using the correct terminal adapter, connect a jumper wire to the DLC terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the body control module (BCM) terminal of the splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 18 | Go to Step 12 |
| 12 | Disconnect the vehicle theft deterrent (VTD). Test the class 2 serial data circuit between the DLC and the splice pack SP205 for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 13 |
| 13 | Using the correct terminal adapter, connect a jumper wire to the DLC terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the BCM terminal of the splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 15 | Go to Step 14 |
| 14 | Turn OFF the ignition. Disconnect the BCM. Test the class 2 serial data circuit of the BCM for an open, a short to ground, or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 25 |
| 15 | Leave the jumper wire connected to the DLC terminal and to the BCM terminal of the splice pack SP205. Connect another jumper wire from the jumper wire connected to the DLC terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the powertrain control module (PCM) terminal of the splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 17 | Go to Step 16 |
| 16 | Turn OFF the ignition. Disconnect the PCM. Test both class 2 serial data circuits of the PCM for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 25 |
| 17 | Turn OFF the ignition. Reconnect the VTD. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 25 |
| 18 | Leave the jumper wire connected to the DLC terminal and to the BCM terminal of the splice pack SP205. Connect another jumper wire from the jumper wire connected to the DLC terminal of the splice pack SP205. Connect the other end of the jumper wire, using correct terminal adapter, to the splice pack SP306 terminal of the splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 23 | Go to Step 19 |
| 19 | Disconnect the splice pack SP306. Inspect for poor connections at the splice pack SP306. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 21 | Go to Step 20 |
| 20 | Repair the class 2 serial data circuit between the splice pack SP205 and the splice pack SP306 for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | |
| 21 | Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP306 until the concern is located: Connect another jumper wire to the splice pack SP205 terminal of the splice pack SP306. Connect the other end of the jumper wire, using correct terminal adapter, to the terminal for the devices connected to splice pack SP306. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 27 | Go to Step 22 |
| 22 | Turn OFF the ignition. Disconnect the module that caused the no communication condition. Test the class 2 serial data circuit between the splice pack SP306 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 25 |
| 23 | Repeat the following steps on the class 2 serial data circuits connected to the splice pack SP205 until the concern is located: Disconnect the jumper wire from the splice pack SP306 terminal of the splice pack SP205. Connect the jumper wire, using correct terminal adapter, to the terminal of the rest of modules connected to splice pack SP205. Turn ON the ignition, leaving the engine OFF. Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 27 | Go to Step 24 |
| 24 | Turn OFF the ignition. Disconnect the module that caused the no communication condition. Test the class 2 serial data circuit between the splice pack SP205 and the respective module for a short to ground or a short to voltage. Turn ON the ignition leaving the engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 25 |
| 25 | Inspect for poor connections at the class 2 serial data circuit of the module that induced the failure. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 26 |
| 26 | Replace the module that induced the failure. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 27 | |
| 27 | Reconnect all of the disconnected modules. Reconnect any other disconnected connectors. Install a scan tool. Turn ON the ignition, leaving the engine OFF. Wait for 10 seconds. The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF the scan tool prior to performing this test. Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all of the displayed DTCs and the DTC status. Did you record any DTCs which begin with a "U" and with a current status? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 28 |
| 28 | Did you record any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 29 |
| 29 | Use the scan tool in order to clear the history DTCs. Did you complete the action? | System OK | |
| IMPORTANT |
|---|
| This test is used for vehicles with Passkey III+ System (PK3+), as vehicle theft deterrent. |
| IMPORTANT |
|---|
| Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. |
Scan Tool Does Not Communicate with Class 2 Device (4.2L w/Immobilizer)
The numbers below refer to the step numbers on the diagnostic table.
- 2: A current DTC, U1300 or U1301, may be retrieved only from the engine control module (ECM), because the ECM is connected to both class 2 and high speed GMLAN buses, but it communicates with the scan tool on high speed GMLAN bus only.
- 3: A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The scan tool communicates with the following modules on the class 2 serial data circuit: The body control module (BCM) The communication interface module (OnStar®), w/UE1 The digital radio receiver (DRR), w/U2K The driver door module (DDM) The driver seat module (DSM), w/AAB The DVD player The electronic brake control module (EBCM) The endgate module (EGM), for XUV The HVAC control module The HVAC control module - rear auxiliary The inflatable restraint sensing and diagnostic module (SDM) The instrument panel cluster (IPC) The liftgate control module (LGM), except XUV The passenger door module (PDM) The power roof module (PRM), for XUV The radio The transfer case shift control module (TCSCM), w/4WD The theft deterrent control module (VTD), w/BAE
- 7: Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
- 9: A poor connection at splice pack SP205 will cause this condition but will not set a DTC.
- 10: An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module on the class 2 network. This condition will not set a DTC.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Retrieve the DTCs from the engine control module (ECM). Is DTC U1300 or U1301 set? | Go to DTC U1300, U1301, or U1305 (5.3L) or DTC U1300, U1301, or U1305 (4.2L) | Go to Step 3 |
| 3 | Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature. Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 4 | Go to Step 7 |
| 4 | Did you record any DTCs in the range of U1000-U1255? | Go to Step 5 | Go to Step 6 |
| 5 | Did you record any DTCs in the range of U1001-U1254? | Go to DTC U1001-U1254 | Go to DTC U1000 |
| 6 | Diagnose the non-communicating module by using the DTC U1001-U2154 procedure for the module which is not communicating. Refer to DTC U1001-U1254 . Did you complete the action? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 7 | Turn OFF the ignition. Disconnect the scan tool from the data link connector (DLC). Inspect for poor connections at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 8 |
| 8 | Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 9 |
| 9 | Disconnect the splice pack SP205. Inspect for poor connections at the splice pack SP205. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 10 |
| 10 | Repair the class 2 serial data circuit between the DLC and the splice pack SP205 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the action? | System OK | |
Scan Tool Does Not Communicate with Class 2 Device (5.3L)
The numbers below refer to the step numbers on the diagnostic table.
- 2: A partial malfunction in the high speed GMLAN serial data circuits uses a different procedure from a total malfunction of the high speed GMLAN data circuits. The following modules are connected to the high speed GMLAN serial data circuits: ECM, for 5.3L Transmission control module (TCM)
- 5: Data link connector terminals 6 and 14 provide the connection to the GMLAN serial data high circuit and the GMLAN serial data low circuit respectively.
- 12: The communication malfunction may have prevented diagnosis of the customer complaint.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | IMPORTANT: Make sure the CANdi module works fine. When functioning properly, CANdi's LED flashes. In the event of a problem, the LED will be constantly illuminated. Turn ON the ignition, with the engine OFF. Attempt to communicate with the modules on high speed GMLAN data bus. Does the scan tool communicate with any module on the GMLAN serial data circuits? | Go to Step 3 | Go to Step 5 |
| 3 | Did you record any DTCs in the range of U2105 to U2199? | Go to DTC U2105-U2199 | Go to Step 4 |
| 4 | IMPORTANT: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Disconnect the scan tool from the data link connector (DLC). Test the high speed GMLAN serial data circuits for the following conditions: An intermittent short to ground An intermittent short to voltage An intermittent short between them - Refer to Diagnostic Aids. An intermittent open on any of the circuits Refer to the following in Wiring Systems: Testing for Intermittent Conditions and Poor Connections Circuit Testing Connector Repairs GMLAN Wiring Repairs Did you find and correct the condition? | Go to Step 13 | Go to Diagnostic Aids |
| 5 | Turn OFF the ignition. Inspect for poor connections at the DLC terminals 6 and 14. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 6 |
| 6 | Disconnect the engine control module (ECM). Turn ON the ignition, with the engine OFF. Attempt to communicate with the transmission control module (TCM). Does the scan tool communicate with the TCM? | Go to Step 7 | Go to Step 9 |
| 7 | Inspect for poor connections at the high speed GMLAN serial data circuits of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 8 |
| 8 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 11 | |
| 9 | Turn OFF the ignition. Disconnect the TCM. Test the high speed GMLAN circuits between the DLC and the TCM and between the TCM and the ECM for the following conditions: An open A short to ground A short to battery A short between them Refer to the following in Wiring Systems: Circuit Testing GMLAN Wiring Repairs Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 10 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 11 | |
| 11 | Reconnect all of the disconnected modules. Install a scan tool. Turn ON the ignition, with the engine OFF. Wait for 10 seconds. The scan tool may require a power up reset before communication will occur due to a short on the high speed GMLAN serial data circuits. Turn OFF or disconnect the scan tool prior to performing this test. Select the Display DTCs function for each module. Record all of the displayed DTCs and the DTC status. Did you record any DTCs which begin with a "U" and with a current status? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 12 |
| 12 | Did you record any DTCs which do not begin with a "U"? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 13 |
| 13 | Use the scan tool in order to clear the history DTCs. Did you complete the action? | System OK | |
| IMPORTANT |
|---|
| Make sure the CANdi module works fine. When functioning properly, CANdi's LED flashes. In the event of a problem, the LED will be constantly illuminated. |
| IMPORTANT |
|---|
| Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. |
Scan Tool Does Not Communicate with High Speed GMLAN Device
The numbers below refer to the step numbers on the diagnostic table.
- 7: This step tests for battery voltage on the signal circuits that are not required.
- 8: This step tests for no battery voltage on the required signal circuits.
- 9: If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
- 10: This step eliminates open circuits as the cause of the malfunction.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Body Control System Schematics Connector End View Reference: Computer/Integrating Systems Connector End Views IMPORTANT: Open the driver door and leave it open during this test. This will disable the retained accessory power (RAP) mode and eliminate this power mode from the power mode parameter list. DEFINITION: This table is used if the observed vehicle power mode does not match the ignition switch position. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Install a scan tool. Turn OFF the ignition. With a scan tool, under the Diagnostic Circuit Check menu, observe the Class 2 Power Mode parameter. Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 3 | Go to Step 7 |
| 3 | Turn the ignition switch to the UNLOCK position. With a scan tool, under the Diagnostic Circuit Check menu, observe the Class 2 Power Mode parameter. Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 4 | Go to Step 7 |
| 4 | Turn ON the ignition, with the engine OFF. With a scan tool, under the Diagnostic Circuit Check menu, observe the Class 2 Power Mode parameter. Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 5 | Go to Step 7 |
| 5 | IMPORTANT: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode. Turn the ignition switch to the CRANK position. With a scan tool, under the Diagnostic Circuit Check menu, observe the Class 2 Power Mode parameter. Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 6 | Go to Step 7 |
| 6 | Turn the ignition switch to the ACCY position. With a scan tool, under the Diagnostic Circuit Check menu, observe the Class 2 Power Mode parameter. Does the displayed power mode parameter match the actual ignition switch position? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 7 |
| 7 | IMPORTANT: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode. Turn OFF the ignition. Disconnect the power mode master (PMM). Hold the ignition switch in the position that indicated the incorrect power mode. With a test lamp attached to a good ground, test the PMM ignition switch inputs for voltage. Refer to Body Control System Description and Operation . Is voltage present on only the inputs specified for the ignition switch position? | Go to Step 8 | Go to Step 9 |
| 8 | IMPORTANT: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode. Hold the ignition switch in the position that indicated the incorrect power mode. With a test lamp attached to a good ground, test the PMM ignition switch inputs for voltage. Refer to Body Control System Description and Operation . Is voltage not present on any inputs specified for the ignition switch position? | Go to Step 10 | Go to Step 12 |
| 9 | Disconnect the ignition switch. Test the PMM ignition switch input circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Test the PMM ignition switch circuits for a short between circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 11 |
| 10 | Disconnect the ignition switch. Test the PMM ignition switch input circuits for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 11 |
| 11 | Inspect for poor connections and terminal tension at the harness connector of the ignition switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 13 |
| 12 | Inspect for poor connections and terminal tension at the harness connector of the PMM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 |
| 13 | Replace the ignition switch. Refer to Ignition Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 15 | |
| 14 | Replace the PMM. Refer to Computer/Integrating Systems Connector End Views for replacement, setup, and programming. Did you complete the replacement? | Go to Step 15 | |
| 15 | IMPORTANT: The engine may start during this procedure. Turn the ignition OFF after verifying all power modes. Reconnect all disconnected components. With a scan tool, under the Diagnostic Circuit Check menu, observe the Class 2 Power Mode parameter. Cycle the ignition switch through all possible positions one at a time. Does the displayed power mode parameter match the actual ignition switch position? | System OK | Go to Step 2 |
| IMPORTANT |
|---|
| Open the driver door and leave it open during this test. This will disable the retained accessory power (RAP) mode and eliminate this power mode from the power mode parameter list. |
| IMPORTANT |
|---|
| The engine may start during this procedure. Turn the ignition OFF after verifying this power mode. |
| IMPORTANT |
|---|
| The engine may start during this procedure. Turn the ignition OFF after verifying this power mode. |
| IMPORTANT |
|---|
| The engine may start during this procedure. Turn the ignition OFF after verifying this power mode. |
| IMPORTANT |
|---|
| The engine may start during this procedure. Turn the ignition OFF after verifying all power modes. |
Power Mode Mismatch
Fail-safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the body control module (BCM) fail to send a power mode message. The fail-safe plan covers modules with discrete ignition signal inputs as well as those modules using exclusively serial data control of power mode.
See also:
• Master Electrical Component List