Scheme 43
Scheme 44
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
- 4: This step is checking for DTCs in the BCM.
- 5: This step is checking for RAP specific DTCs.
| Step | Action | Yes | No |
|---|---|---|---|
| 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 establish communication with the body control module. Does the scan tool communicate with the BCM? | Go to Step 3 | Go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE |
| 3 | IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the BODY CONTROL SYSTEM DESCRIPTION AND OPERATION , for a list of the power mode states that correspond to each ignition switch position. Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions? | Go to Step 4 | Go to POWER MODE MISMATCH |
| 4 | Select the BCM display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Step 5 | Go to the Symptoms list in the appropriate service category |
| 5 | Does the scan tool display B1477 or B1478? | Go to Diagnostic Trouble Code (DTC) List | Go to Symptoms - Retained Accessory Power |
| IMPORTANT |
|---|
| The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. |
Diagnostic System Check - Retained Accessory Power
The numbers below refer to the step numbers on the diagnostic table.
- 2: Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
- 3: Tests for voltage at the coil side of the RAP relay. The RAP fuse supplies power to the coil side of the RAP relay.
- 4: Verifies that the BCM is providing ground to the RAP relay.
- 5: Tests the control circuit side of the RAP relay.
- 10: After replacement of the BCM you must calibrate the new module for proper operation.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Retained Accessory Power (RAP) Schematics | |||
| 1 | Did you perform the Diagnostic System Check - Retained Accessory Power (RAP)? | Go to Step 2 | Go to Diagnostic System Check - Retained Accessory Power |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the RAP relay ON and OFF. Does the RAP relay turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 |
| 3 | Turn OFF the ignition. Remove the RAP relay. Turn ON the ignition, with the engine OFF. Test the battery voltage circuit of the RAP relay with a test lamp. Does the test lamp illuminate? | Go to Step 4 | Go to Step 8 |
| 4 | Connect a test lamp between the RAP relay control circuit of the RAP relay and the battery positive voltage circuit of the RAP relay. With a scan tool, command the RAP relay ON and OFF. Does the test lamp turn ON and OFF with each command? | Go to Step 6 | Go to Step 5 |
| 5 | Test the control circuit of the RAP relay for an open or short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
| 6 | Inspect for poor connections and terminal damage at the RAP relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
| 7 | Inspect for poor connections at the harness connector of the BCM. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 8 | Repair the battery positive voltage circuit of the RAP relay. Refer to WIRING REPAIRS . Did you complete the repair? | Go to Step 11 | |
| 9 | Replace the RAP relay. Did you complete the replacement? | Go to Step 11 | |
| 10 | IMPORTANT: Replace the BCM. Refer to BODY CONTROL MODULE REPLACEMENT . Did you complete the replacement? | Go to Step 11 | |
| 11 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset? | Go to Step 2 | System OK |
| IMPORTANT |
|---|
| Replace the BCM. Refer to BODY CONTROL MODULE REPLACEMENT . |
DTC B1477
The numbers below refer to the step numbers on the diagnostic table.
- 2: Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
- 3: Tests for battery voltage at the coil side of the RAP relay. The RAP fuse supplies power to the coil side of the RAP relay.
- 4: Verifies that the BCM is providing ground to the RAP relay.
- 5: Tests if ground is constantly being applied to the RAP relay.
- 10: After replacement of the BCM you must calibrate the new module for proper operation.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Retained Accessory Power (RAP) Schematics | |||
| 1 | Did you perform the Diagnostic System Check - Retained Accessory Power (RAP)? | Go to Step 2 | Go to Diagnostic System Check - Retained Accessory Power |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the RAP relay ON and OFF. Does the RAP relay turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 |
| 3 | Turn OFF the ignition. Remove the RAP relay. Turn ON the ignition, with the engine OFF. Probe the battery positive voltage circuit of the RAP relay with a test lamp. Does the test lamp illuminate? | Go to Step 4 | Go to Step 8 |
| 4 | Connect a test lamp between the RAP relay control circuit and the battery positive voltage circuit of the RAP relay. With a scan tool, command the RAP relay ON and OFF. Does the test lamp turn ON and OFF with each command? | Go to Step 6 | Go to Step 5 |
| 5 | Test the control circuit of the RAP relay for a short to voltage or a short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
| 6 | Inspect for poor connections at the RAP relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
| 7 | Inspect for poor connections and terminal damage at the harness connector of the BCM. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 8 | Repair the battery positive voltage circuit of the RAP relay. Refer to WIRING REPAIRS . Did you complete the repair? | Go to Step 11 | |
| 9 | Replace the RAP relay. Did you complete the replacement? | Go to Step 11 | |
| 10 | IMPORTANT: Replace the BCM. Refer to BODY CONTROL MODULE REPLACEMENT . Did you complete the replacement? | Go to Step 11 | |
| 11 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset? | Go to Step 2 | System OK |
| IMPORTANT |
|---|
| Replace the BCM. Refer to BODY CONTROL MODULE REPLACEMENT . |
DTC B1478