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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 514 (Engine Controls/Fuel - Hybrid (LZ1) - DTC P0351 To DTC P3449 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0685, P0689, P0690, or P1682 >> Circuit/System Description

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.

There are 2 ignition voltage circuits supplied to the engine control module (ECM). One is supplied by the powertrain relay and the other is supplied by the Run/Crank relay. The ECM monitors and compares the ignition voltage supplied by the 2 relays.