Circuit Description
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) controls the IGN 1 Relay (L26, L32) or IGNITION MAIN PCB Relay (LS4) which is located in the underhood fuse block. The switch contacts of the relay deliver a B+ signal to the following components:
- The antilock brake system (ABS) functions
- The AC compressor relay
- The crank relay
- The HVAC control head
- The instrument panel cluster (IPC)
- The powertrain control module (PCM)
- The sensing and diagnostic module (SDM)
- The transmission solenoids
The BCM will energize the relay when the vehicle is in the RUN or CRANK power mode. The BCM supplies B+ on the ignition 1 voltage circuit (control circuit) to energize the relay. The relay ground circuit is from G113. If a short or open/high resistance in the ignition 1 voltage circuit or an open in the ground circuit occurs, the BCM will set a B1428 and the relay will not energize.