Computers and Control Systems: Service Precautions

Aftermarket electrical and vacuum equipment is defined as any equipment that connects to the vehicle's electrical or vacuum systems that is installed on a vehicle after the vehicle leaves the factory. No allowances in the vehicle design have been made for aftermarket equipment.

NOTE:
^ Do not attach add-on vacuum operated equipment to this vehicle. The use of add-on vacuum equipment may result in damage to vehicle components or systems.
^ Connect any add-on electrically operated equipment to the vehicle's electrical system at the battery (power and ground) in order to prevent damage to the vehicle.

Even if add-on electrical equipment is installed to strict guidelines, this equipment may still cause the powertrain system to malfunction. Equipment that is not connected to the vehicle's electrical system, such as portable telephones and radios, can also cause a malfunction. The first step in diagnosing any powertrain problem is to eliminate all aftermarket electrical equipment from the vehicle. If the problem still exists, diagnose the problem in the normal manner.