Test Description
The number below refers to the step number on the diagnostic table.
- 3: If DTC B1001 is set as current, reprogram the module.
| Step | Action | Yes | No |
|---|---|---|---|
| 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 | Install a scan tool. Turn ON the ignition, with the engine OFF. Retrieve current DTCs with the scan tool. Is DTC B1001 retrieved as current? | Go to Step 3 | Go to Diagnostic Aids |
| 3 | Perform the programming or setup procedure for the module that set DTC B1001. Refer to Control Module References for the proper procedure. Does DTC 1001 reset? | Go to Step 4 | System OK |
| 4 | IMPORTANT: Perform the programming or setup procedure for the module. Replace the module that set DTC B1001. Refer to Control Module References for the proper procedure.Did you complete the replacement? | System OK | |
| IMPORTANT |
|---|
| Perform the programming or setup procedure for the module. |
DTC B1001
The numbers below refer to the step numbers on the diagnostic table.
- 7: The module which was not communicating due to an open in the GMLAN serial data circuits may have set Loss of Communication DTCs for those modules that it was monitoring.
- 9: The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.
| 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 the ignition OFF. Test the following circuits of the module that is not communicating for an open or a short to ground. The battery positive circuits The battery voltage output circuits The ignition positive voltage circuits The ignition voltage output circuits 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 3 |
| 3 | Test the ground 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 4 |
| 4 | Test the GMLAN 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 7 | Go to Step 5 |
| 5 | Test the following circuits of the module that is not communicating for poor connections: The battery positive voltage circuits The battery voltage output circuits The ignition positive voltage circuits The ignition voltage output circuits The ground circuits The GMLAN serial data circuits 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 9 | 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 9 | |
| 7 | Install a scan tool. Turn the ignition ON, 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 System Check - Vehicle in Vehicle DTC Information | Go to Step 8 |
| 8 | Use the scan tool in order to clear the DTCs. Did you complete the action? | Go to Step 9 | |
| 9 | 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 System Check - Vehicle in Vehicle DTC Information | Go to Step 10 |
| 10 | 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 | |
DTC U2105-U2199
| IMPORTANT | The following steps must be completed before using the symptom tables. |
- Perform the «Diagnostic System Check - Vehicle»(ref-196940-S27536559152005101000000) in Vehicle DTC Information before using the symptom tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data links.
- Review the system operation in order to familiarize yourself with the system functions. Refer to: «Data Link Communications Description and Operation»(ref-196943-S22911853872005101000000) «Body Control System Description and Operation»(ref-196943-S03068761522005101000000) «Retained Accessory Power (RAP) Description and Operation»(ref-196943-S42419798172005101000000)
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 Circuit Testing or 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 2 |
| 2 | Test the ground circuit from pin 4 of the DLC for an open or high resistance. Refer to Circuit Testing or 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 3 |
| 3 | Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections or 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 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 loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
- 4: The following DTCs may be retrieved with a history status. These DTCs 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 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
- 10: Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
- 12: This step will isolate a wiring problem or a module malfunction.
- 13: An open circuit at this point will cause a loss of communication with the vehicle.
- 14: This step analyzes the specific branch circuit for a malfunction.
- 19: If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.
- 20: The communication concern 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 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up |
| 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 history DTCs U1300, U1301 or U1305 retrieved from any module? | Go to Step 5 | Go to Step 6 |
| 5 | IMPORTANT: Turn the ignition ON, 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 18 | Go to Step 6 |
| 6 | Are U1000 or U1255 the only DTCs displayed in the previously specified range? | Go to DTC U1000 and U1255 | Go to DTC U1001-U1254 |
| 7 | Diagnose the non communicating module by using the DTC U1001 - U1254 Lost Communications with XXX procedure for the module which is not communicating. The DTC U1001 - U1254 Lost Communications with XXX procedure will determine which module 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 the ignition OFF. Disconnect the scan tool from the data link connector (DLC). Inspect for poor connections and terminal tension at the DLC. 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 ground circuits of the DLC for an open or high resistance. 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 | Isolate the power mode master (PMM) module from all other modules on the class 2 serial data circuit by backing out only the class 2 serial data terminals from the PMM harness connectors, except for the one class 2 serial data circuit that is routed to the DLC, pin 2. To identify which module is the PMM refer to Body Control System Description and Operation , also refer to Data Link Connector (DLC) Schematics for the circuit ID. Connect all of the PMM harness connectors with the extracted class 2 serial data circuit terminals. Turn the ignition ON, with the engine OFF. Attempt to communicate with the PMM. Does the scan tool communicate with the PMM? | Go to Step 12 | Go to Step 11 |
| 11 | Test the class 2 serial data circuits between the DLC and the PMM for the following conditions. Turn ON the ignition when testing for a short to voltage: High resistance Open Short to ground Short to voltage Test the following circuits of the PMM for an open or high resistance: 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 Refer to Circuit Testing and Wiring Repairs in Wiring SystemsDid you find and correct the condition? | Go to Step 18 | Go to Step Step 17 |
| 12 | Perform the following for each class 2 serial data branch circuit, in order to determine if the concern is located within the class 2 serial data branch circuits or the modules connected to the class 2 bus: Turn the ignition OFF. One at a time, replace each terminal in the PMM harness connectors. Turn the ignition ON, with the engine OFF. Attempt to communicate with any module connected to the class 2 serial data branch circuit after reinstalling it's class 2 serial data terminal. Record which branch of the class 2 serial data circuit causes a loss of communication if one occurs in the above items. Does the scan tool communicate with all modules connected to the class 2 serial data circuit after all the branch circuits have been reconnected? | Go to Step 13 | Go to Step 14 |
| 13 | Inspect for poor connections and terminal tension at the harness connector of the PMM harness connector that contains the discreet class 2 serial data circuit for the DLC. Did you complete the action? | Go to Step 18 | |
| 14 | Turn the ignition OFF. Using the record made in step 12, identify each module on that branch of the class 2 serial data circuit and disconnect there harness connectors containing the class 2 serial data circuits. Using the record made in step 12 again, test the branch circuits that caused a No Comm with class 2 for the following. Turn the ignition ON when testing for a short to voltage or short to ground. Did you find and correct the problem? | Go to Step 18 | Go to Step 15 |
| 15 | The concern is a malfunctioning module on the class 2 serial data branch circuit recorded in step 12. Turn the ignition OFF. One at a time, starting with the first module on the malfunctioning class 2 serial data branch circuit closest to the PMM, start attaching modules back onto that branch circuit. Turn the ignition ON, with the engine OFF. Attempt to communicate with the reinstalled modules connected to the malfunctioning branch. Repeat items 1 through 4 attempting to lose communication. If communication is lost, record the last module reconnected proceed down the table and discontinue the repeating of items 1 through 4. Does the scan tool communicate with all the modules connected to the class 2 serial data circuit? | Go to Step 18 | Go to Step 1 |
| 16 | Inspect for poor connections and terminal tension at the harness connector of the reconnected module that causes a loss of communication. 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 18 | Go to Step 17 |
| 17 | Replace the suspect module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 18 | |
| 18 | Connect all of the modules. Connect all the connectors. Install a scan tool. Turn the ignition ON leaving the engine OFF. IMPORTANT: 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 or disconnect the scan tool before you display DTCs. Wait for 10 seconds. 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 your record any DTCs which begin with a letter U and with a current status? | Go to Step 20 | Go to Step 19 |
| 19 | Did you record any DTCs which do not begin with a letter "U"? | Go to Step 20 | Go to Step 22 |
| 20 | Diagnose the DTCs as directed by the diagnostic procedures for the particular module or concern. Did you complete the action? | Go to Step 21 | |
| 21 | Did you diagnose all of the DTCs? | Go to Step 22 | Go to Step 20 |
| 22 | Clear the DTCs using the scan tool. Did you complete the action? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| IMPORTANT |
|---|
| Turn the ignition ON, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. |
| IMPORTANT |
|---|
| 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 or disconnect the scan tool before you display DTCs. |
Scan Tool Does Not Communicate with Class 2 Device
The numbers below refer to the step numbers on the diagnostic table.
- 6: This step tests for battery voltage on the incorrect signal circuits.
- 7: This step tests for no battery voltage on the required signal circuits.
- 8: 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.
- 9: 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 and Master Electrical Component List in Wiring Systems 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. | |||
| 1 | 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 2 | Go to Step 6 |
| 2 | 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 3 | Go to Step 6 |
| 3 | Turn the ignition switch to the RUN position, 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 4 | Go to Step 6 |
| 4 | 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 5 | Go to Step 6 |
| 5 | 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 6 |
| 6 | 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), body control module (BCM) on this vehicle. Hold the ignition switch in the position that indicated the incorrect power mode. With a DMM attached to a good ground, test all the PMM ignition switch inputs for positive voltage. Refer to Body Control System Description and Operation for the state of the input circuits at a specified ignition switch position. Is voltage present on only the inputs selected by the ignition switch position? | Go to Step 7 | Go to Step 8 |
| 7 | 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 DMM 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 only inputs specified for the ignition switch position? | Go to Step 9 | Go to Step 11 |
| 8 | 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 14 | Go to Step 10 |
| 9 | 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 14 | Go to Step 10 |
| 10 | 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 14 | Go to Step 12 |
| 11 | 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 14 | Go to Step 13 |
| 12 | Replace the ignition switch. Refer to Ignition Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 14 | |
| 13 | Replace the PMM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 14 | |
| 14 | Connect 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 1 |
| 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. |
Power Mode Mismatch
Body Control System Description and Operation
The body control module (BCM) has a bussed electrical center integrated into the housing. Body control relays and fuses are installed directly on the BCM which simplifies wiring and junction blocks on the vehicle. The body control system consists of the BCM and its associated controls. Battery positive voltage is provided to the BCM from the instrument panel (I/P) BATT 2 fuse in the underhood fuse block. The module grounds are wired to ground G201 and G301. The BCM is wired to the class 2 serial data communication bus as well as discrete input and output terminals to control the functions of the vehicles body.
Power Mode Description and Operation
Power to many of this vehicle's circuits are controlled by the module that is designated the Power Mode Master (PMM). This vehicle's PMM is the Body Control Module (BCM). The PMM controls which power mode (Run, Accessory, Crank, Retained Accessory Power, or Off) is active.