U codes Chevrolet
This vehicle is known for having data line problems. The data line carries digital data between different control modules. If a module shorts out, it can inject voltage onto the line which scrambles the digital data. The data line can also short to ground or break.
Data line issues are difficult to diagnose, so bring plenty of patience to your job.
Start with a factory wiring diagram (eautorepair.net). Next test the resistance across the 2 high speed data line wires at the diagnostic link connector (DLC). You should get a reading of 60 ohms. If you get a higher reading (120 ohms), disconnect one module at a time between the PCM and Body Control Module and jumper across the data line at that module. If resistance falls to the lower level and the vehicle operates properly, turn your attention to why that module may have failed. Check for proper power and ground to the module. .
© 2012 Rick MuscoplatPosted on by Rick Muscoplat