Circuit Description
The Body Control Module (BCM) interfaces with the vehicle's power distribution system through the RAP relay. The RAP relay allows the BCM to control the application of power to the feed circuits of the Sun-roof and the power windows. When the ignition switch is in either the ACC or the RUN position, the BCM energizes the RAP relay by grounding the RAP relay control circuit.
The BCM turns off the RAP relay when the ignition switch is in the START position. The RAP feature therefore disables during engine cranking.
When the ignition switch turns from ON or ACCESSORY to UNLOCK or OFF, with all of the vehicle doors closed, the BCM leaves the RAP relay energized for 10 minutes, or until any vehicle door opens and the BCM detects a ground signal in one of the door ajar circuits.
Conditions for Running the DTC
The BCM must be commanding the RAP relay to energize.
Conditions for Setting the DTC
| • | The BCM detects a short to battery in the RAP relay control circuit when the BCM is trying to energize the RAP relay. |
| • | The condition above must be present for more than 300 milliseconds. |
Action Taken When the DTC Sets
| • | The RAP relay powered functions will not operate. |
| • | The BCM stores DTC B1478 in memory. |
Conditions for Clearing the DTC
| • | A current DTC B1478 will clear if the short to battery in the RAP relay control circuit is no longer detected by the BCM when the RAP relay is commanded to energize. |
| • | A history DTC B1478 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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This step verifies that the Body Control Module (BCM) is providing ground to the RAP relay.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Retained Accessory Power (RAP) Diagnostic System Check? | Go to Step 2 | |
Does the RAP Relay turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 5 | Go to Step 4 | |
4 | Test the RAP relay control circuit 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 9 | Go to Step 6 |
5 | Inspect for poor connections at the RAP relay. 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 7 |
6 | Inspect for poor connections at the harness connector of the body control module (BCM). 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 8 |
7 | Replace the RAP relay. Did you complete the repair? | Go to Step 9 | -- |
8 |
Important: Perform the set up procedure for the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair? | Go to Step 9 | -- |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
