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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 92 (Engine Controls - Self-Diagnostics - 6.6L Diesel) >> Diagnostic Tests >> DTC P1639: 5-Volt Reference 2 Circuit >> Test Description

Test Description

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 8

    If the circuit is shorted to the Transmission Control Module (TCM) MIL request circuit, the scan tool will show skewed BARO and boost sensor readings just after the ignition is turned ON. The sensor readings will then return to normal in under 1 second.

  2. 11

    This vehicle is equipped with a ECM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the ECM is being replaced, the new ECM must be programmed.

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