Circuit/System Description

WARNING: This page is about a different car, the 2012 GMC Yukon, 2012 Chevrolet Tahoe, and 2012 Cadillac Escalade. 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 drive motor generator battery control module will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the drive motor generator battery control module to the hybrid powertrain control module (HPCM) through serial data. The hybrid powertrain control module is the host controller for diagnostic trouble code (DTC) information.

The vehicle is equipped with a high voltage isolation monitor feature. The purpose of the high voltage isolation circuit is to test the resistance between the high voltage positive and negative direct current (DC) bus and chassis ground. The drive motor generator battery control module only runs this test when the ignition transitions from ON to OFF and the high voltage contactor relays have opened. The drive motor generator battery control module has an internal isolation sensor that measures the resistance between the high voltage DC positive and negative bus and chassis ground. The drive motor generator battery control module runs an internal self check of this sensor circuit. If the internal self check fails DTC P1AE6 will set. The drive motor generator battery control module sends an AC signal over the DC bus and monitors its amplitude. A low amplitude or collapsed return signal indicates a loss of resistance to chassis ground and a loss of isolation will be indicated by the drive motor generator battery control module. This DTC indicates that the fault is in the drive motor generator battery. Because this diagnostic runs after system power down, the diagnostic status does not get reported until the next key cycle.