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Home >> Pontiac >> 2001 >> Aztek Base, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 89 (Engine Control System Self-Diagnostics - 3.1L Engine) >> Diagnostic Tests >> DTC P1639: 5-Volt Reference 2 Circuit >> Test Description
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Test Description

WARNING: This page is about a different car, the 2002 Pontiac Grand Prix, 2002 Chevrolet Malibu, and 2002 Buick Century. 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. 7

    The ignition must be turned off, and the PCM powered down or the test may become inaccurate.