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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 155 (Engine Controls Self-Diagnostics - 5.7L - Bi-Fuel) >> Diagnostic Tests >> DTC P0135 & P0155: Ho2S Bank 1& 2 Sensor 1 Heater Circuit >> Test Description

Test Description

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers in the diagnostic procedures.

  1. 2

    As the heater warms the oxygen sensor to operating temperature, the HO2S will output a voltage in relation to the amount of oxygen in the exhaust. With the ignition ON and the engine OFF, the exhaust usually contains a high oxygen content. With the engine OFF, the HO2S voltage will usually decrease from the initial bias voltage due to the high oxygen content.

  2. 6

    This step tests for a proper HO2S heater ignition feed and ground supply.

  3. 7

    This step tests for proper control module and signal circuit operation.
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