Test Description

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

The numbers below refer to the step numbers on the diagnostic table.

1) - A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.
2) - A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.
3) - The malfunction is due to an open in the class 2 serial data circuit or an open in the module.
7) - The module which was not communicating due to an open in the class 2 serial data circuit may have set Lost Communication DTCs for those modules that it was monitoring.
9) - The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

Fig 1: DTC U1001-U1254 Diagnosis (Steps 1-8)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC U1001-U1254 Diagnosis (Steps 9-10)

Courtesy of GENERAL MOTORS CORP.