DTC B1478: Retained Accessory Power Circuit High: Description

BCM controls Retained Accessory Power (RAP) feature. RAP allows the radio, power windows and power sunroof (if equipped) operation for 10 minutes after ignition is turned from RUN or ACC positions to LOCK position, or until a vehicle door opens. BCM interfaces with vehicle power distribution system through the RAP time delay relay. RAP time delay relay allows BCM to control application of power to RADIO fuse and PWR WINDOWS, PWR SUNROOF circuit breaker. When ignition switch is in either ACC or RUN positions, BCM energizes RAP time delay relay by grounding RAP time delay relay control circuit. See Figure .

BCM turns off RAP time delay relay when ignition is in START position. RAP feature is disabled during engine cranking. When ignition is turned from RUN to LOCK or OFF positions, with all doors closed, BCM leaves RAP time delay relay energized for 10 minutes, or until any vehicle door opens (BCM detects door open by a ground signal on one of the door ajar circuits).

DTC B1478 will set when BCM detects a short to battery voltage or an open in RAP time delay relay control circuit for more than 0.3 second when it is trying to energize the relay. No driver warning message will be issued. A current DTC B1478 will clear when a short to battery voltage or open on the RAP time delay relay control circuit is no longer detected. A history DTC B1478 will clear after 100 consecutive ignition cycles if conditions for setting DTC are no longer present. A scan tool may be used to clear DTC B1478.