Test Description

WARNING: This page is about a different car, the 2002 Buick Regal 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 on the diagnostic table.

1. A Lost Communication with XXX DTC with a history status may indicate the cause of U1000.
2. The modules that is not communicating is the likely cause of U1000 or U1255 being set.
The following modules communicate on the class 2 serial data circuit:
- PCM
- EBCM
- SDM
- IPC
- BCM
- HVAC Control Module
- VIU
5. The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
6. The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
7. The module that was not communicating may have set Lost Communication with XXX DTCs for those modules that the module was monitoring.
11. The modules that communicate indicate the module that cannot communicate. You must clear the DTC from the modules in order to avoid future misdiagnosis.
13. If all modules are communicating, the module that set U1000 may have done so due to some other condition.
14. The module that set U1000 is the likely cause of the malfunction.

Fig 1: Identifying DTC U1000 and U1255 Diagnostic Table (1 Of 2)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Identifying DTC U1000 and U1255 Diagnostic Table (2 Of 2)

Courtesy of GENERAL MOTORS CORP.