_GM Retained Accessory Power
Description and Operation
Retained Accessory Power (RAP) Power Mode
Retained Accessory Power (RAP) is a power mode that permits the operation of some accessories for up to 10 minutes after the ignition switch is turned OFF. The RAP power mode is enabled by the Body Control Module (BCM). The BCM controls certain body functions by sending out a Class_2 message via the serial data link, which enables/disables other modules at the beginning/end of the RAP power mode. Some BCM features, such as the interior courtesy lamps will function after the 10 minute RAP time limit has elapsed. This is normal, and does not mean the RAP power mode is malfunctioning. The BCM enables the following functions in the RAP Power Mode:
- The windshield wipers and washer through the RAP/Adaptive Cruise Control (ACC) relay.
- The right and left power windows through the RAP/ACC relay.
- Any Class_2 module that functions in RAP power mode and is not connected to the RAP/ACC relay, is controlled by the BCM via Class_2 power mode messages. As an example, the radio works in RAP power mode because the BCM sends a Class_2 message stating that the power mode is RAP.
RAP is disabled when:
- A door is opened.
- Low battery voltage is detected by the BCM.
- The ignition switch transitions from OFF to ON or ACC.
- 10 minutes have elapsed after the ignition was turned OFF.
The BCM monitors the ignition switch position, battery voltage and passenger compartment door status, to determine whether RAP power mode should be enabled. If the ignition switch transitions from ON to OFF, the battery voltage is within the acceptable range, and the passenger compartment doors are closed, the BCM enables RAP power mode. After 10 minutes have elapsed, the BCM sends a Class_2 message to the serial data network. This message commands the other modules that are in power mode by the BCM to stop functioning.
RAP/ACC Relay
The BCM controls the RAP/ACC relay coil circuit using low side drive. The output of the relay is used to supply battery voltage to the windshield wipers and power windows. The RAP/ACC relay also provides voltage to the windshield wipers and power windows when the Accessory and Run power modes are selected.
Schematics
