GM Service Manual Online
For 1990-2009 cars only

Do not connect aftermarket accessories into the following circuits:

Warning: Refer to SIR Warning in the Preface section.

    â€¢ SIR circuits, all such circuits are indicated on circuit diagrams with the SIR symbol.

Caution: Refer to OBDII Symbol Description Caution in the Preface section.

    â€¢ OBD II circuits, all such circuits are indicated on circuit diagrams with the OBD II symbol.

Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problems.

Possible causes of vehicle problems related to aftermarket accessories include:

    â€¢ Power feeds connected to points other than the battery
    â€¢ Antenna location
    â€¢ Transceiver wiring located too close to vehicle electronic modules or wiring
    â€¢ Poor shielding or poor connectors on antenna feed line
    â€¢ Check for recent service bulletins detailing installation guidelines for aftermarket accessories.