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 class 2 serial data modules.
- This test is used for a total class 2 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 U1001-U1254 for diagnostics.
- The body control module (BCM) detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must be connected to the DLC for any other module to communicate with the scan tool.
- An open in the class 2 serial data circuit between JX 205 and a module(s) will only effect the specific module(s). This type of failure will set a loss of communication DTC for each module effected, and the other modules will still communicate.
- An open between the data link connector (DLC) and JX 205 will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
- The engine may not start when there is a total malfunction of the class 2 serial data circuit.
The following conditions may cause a total loss of low speed GMLAN data communication:
- The low speed GMLAN serial data circuit shorted to ground or voltage.
- A module internal malfunction that causes a short to voltage or ground on the low speed GMLAN circuit.
- An open in the DLC ground circuit may cause a scan tool loss of communication, while the modules still communicate.
- When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set:
- U1300
- U1301
- U1305