Diagnostic Aids

WARNING: This page is about a different car, the 2002 Pontiac Aztek and 2002 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

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.
When the class 2 serial data circuit is shorted to ground, DTC U1300 or DTC U1305 will be set. Refer to DTC U1300, U1301, or U1305 (Generic Short DTC) .
When the class 2 serial data circuit is shorted to B+, DTC U1301 or DTC U1305 will be set. Refer to DTC U1300, U1301, or U1305 (Generic Short DTC) .
Disconnecting modules and turning the ignition switch to RUN may cause DTCs to be set in these modules. Check for DTCs in each module upon completion of the required repair.