Diagnostic Aids

WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

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.
An open in the class 2 serial data circuit between the DLC and the BCM will only effect the scan tool communication and will not effect module to module communication
An open between the data link connector (DLC) and The BCM 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 class 2 serial data circuit shorted to ground or voltage.
- A module internal malfunction that causes a short to voltage or ground on the class 2 serial data circuit.
When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set as history. If the short is removed and communication returns, these DTCs indicate an intermittent condition.
- U1300
- U1301
- U1305