Checking Aftermarket Accessories

Do not connect aftermarket accessories into the following circuits:

• SIR circuits, all such circuits are indicated on circuit diagrams with the SIR symbol.
  NOTE: Refer to OBDII SYMBOL DESCRIPTION NOTICE in Cautions and Notices.
• 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:

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