Toyota Corolla 1970-1987 Repair Guide

Communication and Add-On Electrical Equipment


The electrical system in your vehicle is designed to perform under reasonable operating conditions without interference between components. Before any additional electrical equipment is installed, it is recommended that you consult your Toyota dealer or a reputable repair facility familiar with the vehicle and its systems.

If the vehicle is equipped with mobile radio equipment and or mobile telephone it may have an effect upon the operation of the ECM. Radio frequency interference (RFI) from the communications system can be picked up by the vehicle's wiring harnesses and conducted into the ECM, giving it the wrong messages at the wrong time. Although well shielded against RFI, the ECM should be further protected through the following steps:

  1. Install the antenna as far as possible from the ECM. Since the ECM is located behind the center console area, the antenna should be mounted at the rear of the vehicle.
  3. Keep the antenna wiring a minimum of eight inches away from any wiring running to the ECM and from the ECM itself. NEVER wind the antenna wire around any other wiring.
  5. Mount the equipment as far from the ECM as possible. Be very careful during installation not to drill through any wires or short a wire harness with a mounting screw.
  7. Insure that the electrical feed wire(s) to the equipment are properly and tightly connected. Loose connectors can cause interference.
  9. Make certain that the equipment is properly grounded to the vehicle. Poor grounding can damage expensive equipment.
  11. Make sure the antenna is trimmed or adjusted for optimum function.