Retained Accessory Power System: Overview GMC Savana H2500

Scheme 1

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 1. This step verifies that the RAP power mode function is malfunctioning by checking functions internally enabled by the BCM.
2. 3. The BCM sends class 2 messages to other control modules via the serial data link, allowing them to operate in RAP power mode. 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.
3. 5. This step is checking for DTCs in the BCM.
4. 6. The presence of DTCs which begin with "U" indicate that the other module is not communicating. The specified procedure will compile all the available information before tests are performed.

Scheme 2

Scheme 3

The numbers below refer to the step numbers on the diagnostic table.

Scheme 4

Scheme 5

1. 2. During the WND RAP relay operation, listen for an audible click. Command the ON and the OFF states. Repeat the commands as necessary.
2. 3. Verifies whether the WND RAP relay has a defect.
3. 4. Tests the control circuit of the WND RAP relay.
4. 5. Tests the ground circuit of the WND RAP relay.