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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1044 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0237 To P0611)) >> Diagnosis >> DTC P0543 >> Circuit Description

Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The engine control module (ECM) uses an intake air heater (IAH) to warm the incoming air for proper cylinder combustion. The ECM grounds the control coil of the IAH relay to energize the heater during cold operation. The ECM sends a bias voltage on diagnostic circuits 1 and 2. If this voltage is not pulled low when the relay is OFF, or is not high with the relay ON, DTC P0543 will set.

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