GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Century 🢒 DTC 🢒 DTC B1477

Circuit Description

The body control module (BCM) interfaces with the vehicle's power distribution system through the retained accessory power (RAP) relay. The RAP relay allows the BCM to control the application of power to the feed circuits of the Sunroof and 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 to LOCK 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.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTCB1477 Retained Accessory Power Circuit Low

Conditions for Setting the DTC
    • The BCM detects no voltage at the RAP relay control circuit when the BCM has not grounded the circuit.
    • The conditions above must be present for more than 300 milliseconds.

Action Taken When the DTC Sets
    • The BCM stores DTC B1477 in memory.
    • The circuits powered by the RAP relay remain powered at all times if the relay control circuit is shorted to ground.
    • The circuits powered by the RAP relay will never be powered if the relay control circuit is open.

Conditions for Clearing the DTC
    • The correct voltage is present at the RAP relay control circuit as detected by the BCM.
    • A history DTC B1477 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.

  1. Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.

  2. This step tests for voltage at the coil side of the RAP relay. The INADV POWER BUS fuse supplies power to the coil side of the RAP relay.

    3.

  3. This step verifies that the BCM is providing ground to the RAP relay.

    4.

  4. This step tests if ground is constantly being applied to the RAP relay.

Step

Action

Yes

No

Schematic Reference: Retained Accessory Power (RAP) Schematics

Connector End View Reference: Computer/Integrating Systems Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the RAP relay ON and OFF.

Does the retained accessory power (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

3

  1. Turn OFF the ignition.
  2. Disconnect the RAP relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a test lamp that is connected to a good ground, probe the RAP relay coil supply voltage circuit at the RAP relay.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4

  1. Connect a test lamp between the RAP relay control circuit and the RAP relay coil supply voltage circuit at the RAP relay.
  2. 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 8

Go to Step 5

5

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 6

6

Test the control circuit of the RAP relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

7

Test the control circuit of the RAP relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

8

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 13

Go to Step 11

9

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 13

Go to Step 12

10

Test the relay coil supply circuit of the RAP relay for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the RAP relay.

Did you complete the repair?

Go to Step 13

--

12

Replace and reprogram the BCM . Refer to Control Module References for replacement, setup and programming.

Did you complete the repair?

Go to Step 13

--

13
  1. Use the scan tool in order to clear the DTCs.
  2. 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