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 adequate system voltage. If the ignition voltage is low, RAP will be disabled in order to conserve power.
| 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 in Data Link Communications |
| 2 | Turn the ignition ON, with the engine OFF. Attempt to establish communication with the body control module (BCM). Does the scan tool communicate with the BCM? | Go to Step 3 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications |
| 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 in Body Control Systems, 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 in Body Control System |
| 4 | Observe Ignition Voltage in the BCM data list with a scan tool. Is Ignition Voltage at least 12 volts? | Go to Symptoms - Retained Accessory Power | Go to Symptoms - Engine Electrical in Engine Electrical |
| 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