Diagnostic Aids
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
- Use the Data Link References to identify the high speed GMLAN serial data modules.
- When testing for a short between the high speed GMLAN (+) and (-) circuits (ECM/PCM disconnected), a resistance reading of 120 ohms is normal. To test for shorts to voltage or ground in the high speed GMLAN (+) and (-) circuits ensure that all modules, resistors and the scan tool are disconnected from the buss. A normal resistance reading across the high speed GMLAN buss with the resistors, all module and scan tool disconnected is infinite ohms.
- This test is used for a total high speed GMLAN communication failure. If only 1 module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
- The engine may not start when there is a total malfunction of the high speed GMLAN serial data bus.
The following conditions may cause a total loss of high speed GMLAN data communication:
- A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
- Any of the high speed GMLAN serial data circuits shorted to ground or voltage
- A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
- An inoperative BCM