Test Description

WARNING: This page is about a different car, the 2003 Pontiac Montana, 2003 Oldsmobile Silhouette, and 2003 Chevrolet Venture. 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 or U1255.

2. The modules which are not communicating are the likely cause of U1000 or U1255 being set. The Video Disc Player and Rear Video/Audio/HVAC Module communicate on the class 2 serial data circuit to the Radio, but do not communicate with the scan tool.

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 which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.

11. The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

13. If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.

14. The module which set U1000 or U1255 is the likely cause of the malfunction.

Fig 1: DTC U1000 And U1255 Diagnostic Specifications (1 Of 2)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC U1000 And U1255 Diagnostic Specifications (2 Of 2)

Courtesy of GENERAL MOTORS CORP.