Circuit/System Description

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

The drive motor generator battery control module is also referred to as the battery energy control module (BECM). The BECM will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the BECM to the hybrid powertrain control module (HPCM) through the Hybrid LAN communication circuit. The HPCM is the host controller for diagnostic trouble code (DTC) information.

The BECM receives a pulse width modulated (PWM) signal from the HPCM called the contactor system request circuit command. The BECM uses this signal to open and close the HV contactor relays. A 5-volt circuit is provided from the BECM to the HPCM. The HPCM uses a PWM signal on the 5-volt circuit to control the contactor system request command signal. If this PWM signal becomes out of range or invalid, the system will use a redundant GM LAN message to command the HV contactor relays Open and Closed.