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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1132 (Power Seat System) >> Diagnostic Information and Procedures >> DTC B3920 or B3921 >> Circuit/System Description

Circuit/System Description

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

The memory seat module (MSM) controls the seat, recline, and lumbar motors via half bridges that are connected to a power rail internal to the module. Power rail 1 includes of the following motors:

The MSM connects all of the motor control circuits on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.0 volts. The MSM checks to see if this reference voltage is shorted to ground or battery before enabling any seat, recline or lumbar motor.