B1477

DTC B1477 RAP Relay Circuit Shorted To GND Or Open:

DTC B1477 RAP Relay Circuit Shorted To GND Or Open (Part 1 Of 2):

DTC B1477 RAP Relay Circuit Shorted To GND Or Open (Part 2 Of 2):

SYSTEM DESCRIPTION
The Body Control Module (BCM) controls the Retained Accessory Power (RAP) feature. The RAP feature allows the following components to operate for 10 minutes (or until a vehicle door opens) after the ignition switch turns from RUN or ACC to LOCK or OFF:
^ The radio
^ The power windows
^ The power sunroof, if equipped

The 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 circuit 75. Circuit 75 then powers the following circuits:
1. Circuit 43: The radio
2. Circuit 143: The power windows and power sunroof

When the ignition switch is in either the ACC or the RUN position, the BCM energizes the RAP relay by grounding circuit 707.

The BCM turns off the RAP relay when the ignition switch is in the START position. The RAP feature therefore disables during engine crank and bulb test. When the ignition switch turns from RUN to LOCK or OFF with all the vehicle doors closed, the BCM leaves the RAP relay energized for 10 minutes, or until any vehicle door opens (the BCM detects a ground signal in circuit 49 or circuit 727).

The RAP feature is not available on the Century Custom model. The following modes have the RAP feature:
^ The Century Limited
^ The Regal Custom
^ The Regal Grand Sport

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to ground or an open in circuit 707 when the RAP relay is de-energized.
^ The BCM is able to test for a short to ground or an open in circuit 707 when attempts to de-energize the RAP relay.
^ All conditions are present for more than 0.3 seconds.

ACTION TAKEN WHEN THE DTC SETS
The BCM stores DTC B1477 in memory.

CONDITIONS FOR CLEARING THE DTC
^ A short to ground or an open in the RAP relay circuit 707 is not longer detected by the BCM when the RAP relay is de-energized.
^ A history DTC B1477 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ You use a scan tool.

DIAGNOSTIC AIDS
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent open or short to ground in circuit 707
- Poor connections at the BCM or the RAP relay terminals
- The RAP relay coil is shorted to ground or open internally
- The BCM is open or shorted to ground internally
^ The DTC B1477 is a history DTC, the fault may be intermittent. Try to perform the tests shown while moving the wires and connectors. Moving the wires and connectors may cause the malfunction to reappear.
^ The DTC B1477 is set on a Century Custom model, permanently disable DTC B0702 by performing the Setup New BCM procedure. Refer to Body Control System Circuit Description. Description and Operation DTC P1626 sets in the Powertrain Control Module (PCM) when the ignition switch is in the RUN position with the BCM disconnected. After you complete the BCM diagnostics and repairs, refer to Computers and Control Systems for additional information on PCM related DTCs. Computers and Control Systems

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step tests for proper vehicle usage of the RAP feature.
3. The Century Custom model is not equipped with the RAP feature. The Setup New BCM procedure permanently disables the BCM from setting DTC B1477 again.
5. This step tests for a short to ground in circuit 240.
6. This step tests for an open in circuit 240.
7. This step tests for a short to ground in circuit 707.
8. This step tests for an open in circuit 707
9. This step tests for a faulty RAP relay.
10. This step determines whether the malfunction is intermittent or the BCM is faulty.