Circuit Description
The retained accessory power (RAP) function allows certain systems such as the radio, the power windows and the sunroof to operate after the ignition switch is turned OFF for 20 minutes. The body control module (BCM) monitors the ignition switch position, the mini wedge (door jamb) switches and the voltage on CKT 755. The BCM will command the RAP relay ON by grounding CKT 755 when all the doors are CLOSED and the ignition switch is switched to the OFF position. If the BCM detects a short to ground in CKT 755 with the RAP relay commanded OFF the DTC B1477 will set.
Conditions for Setting the DTC
| • | When the BCM does not detect battery voltage on CKT 755 (shorted to ground) with the RAP relay commanded OFF. |
| • | The system voltage must be between 9.0-16.0 volts. |
| • | The above conditions must be met for 0.5 seconds. |
Action Taken When the DTC Sets
| • | If CKT 755 is open the radio, the power windows and the sunroof (if equipped) will not operate after the ignition switch is turned OFF and all the doors are closed. |
| • | If CKT 755 is shorted to ground the radio, the power windows and the sunroof (if equipped) will operate after the ignition switch is turned OFF with a door open. |
Conditions for Clearing the MIL/DTC
| • | This DTC will clear immediately after the condition for setting the fault is corrected with the ignition switch in the OFF position and a door open. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | Use a scan tool in order to clear the history and current DTCs. |
Diagnostic Aids
Important: Use the appropriate probe from the connector test adapter kit J 35616 for any probing of the bussed electrical center (BECs) in this table to avoid damage to the BECs.
| • | Always diagnose the first current DTC listed on the scan tool. |
| • | The scan tool must display DTC B1477 as a current code before performing diagnostics. |
| • | Perform a visual inspection of the wiring, the terminals and the connectors. |
| • | Refer to Intermittents and Poor Connections in Wiring Systems. |
Test Description
Step number(s) below refer to the same step number(s) in the Diagnostic Table.
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This step determines if CKT 755 is shorted to ground or if there is an open in one of the circuits.
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This step determines if the BCM is defective or if CKT 755 is shorted to ground.
-
This step verifies the condition of the RAP relay fuse and CKT 542 to the RAP relay in the LBEC.
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This step determines if the RAP relay fuse is open or the UBEC is defective.
-
This step determines if the BCM is defective, or if there is an open circuit between the BCM and the RAP relay.
-
This step determines if the RAP relay is defective or if CKT 755 is open between the relay and the BCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the BCM Diagnostic System Check performed? | -- | ||
2 |
Does the radio or the power windows still operate? | -- | ||
3 |
Does the J 39200 DMM read battery voltage? | -- | ||
4 |
Do the power locks and mirrors operate? | -- | ||
5 | Test both sides of the RAP fuse with a test lamp to ground. Does the test lamp light on both sides of the RAP fuse? | -- | ||
6 | Does the test lamp light on either side of the RAP fuse? | -- | Go to Step 7 | Go to Step 8 |
7 | Locate and repair the short to ground in CKT 542 (RED) between the UBEC and the RAP relay (in the LBEC). Is the repair complete? | -- | Go to Step 16 | -- |
8 | Replace the UBEC. Is the repair complete? | -- | Go to Step 16 | -- |
9 |
Does the J 39200 DMM read battery voltage? | -- | ||
10 |
Is the resistance at or above the specified value? | 65 ohms | ||
11 | Locate and repair the open in CKT 755 (BLK) between the BCM and the RAP relay. Is the repair complete? | -- | -- | |
12 | Replace the RAP relay Is the repair complete? | -- | -- | |
13 | Locate and repair the open in CKT 542 (RED) between the UBEC and the RAP relay. Is the repair complete? | -- | -- | |
14 | Locate and repair the short to ground in CKT 755 (BLK) between the BCM and the RAP relay. Is the repair complete? | -- | -- | |
15 |
Is the repair complete? | -- | System OK | -- |
16 | Clear the DTCs. Refer to Clearing DTCs . Is the repair complete? | -- | System OK | -- |
