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 number below refers to the step number in the diagnostic procedures.

4

A short to voltage on the 5-volt reference circuit will cause DTC P1639 to set.

7

This step tests the signal circuit of the BARO sensor for a short to voltage. The short may backfeed through the sensor to the 5-volt reference circuit causing the DTC P1639 to set.

8

This step tests the signal circuit of the boost sensor for a short to voltage. The short may backfeed through the sensor to the 5-volt reference circuit causing the DTC P1639 to set.

9

This step tests the signal circuit of the EGR vacuum sensor for a short to voltage. The short may backfeed through the sensor to the 5-volt reference circuit causing the DTC P1639 to set.