Jeep Wrangler/YJ 1987-1995 Repair Guide

American Motors Solid State (Renix) Ignition System


All 1987-90 2.5L engines are equipped with electronically controlled fuel injection. Therefore, the electronic ignition system is different from that used on carbureted engines. These engines are equipped with the American Motors Solid State (Renix) ignition system which consists of:

Spark plugs
Secondary ignition cables
Ignition coil
Solid state Ignition Control Module (ICM)
An Engine Control Unit (ECU)
Forty tooth rotor (in the distributor)
TDC sensor (mounted at the rear of the engine on the flywheel housing)

The control module consists of a solid state ignition circuit and an integrated ignition coil each of which can be removed and serviced separately. Spark timing control is determined by the Ignition Control Module (ICM). Signals from the ECU relay information about engine load and other driving conditions to both the ICM and fuel injection system electronic control components.

Electrical feed to the ICM is through terminal A of connector 1 (please see the illustration). Electrical feed occurs only when the ignition switch is in the START and RUN positions. Terminal B of connector 1 is grounded at the engine oil dipstick bracket, along with the ECU ground wire and the O 2 sensor ground.


Primary System

Primary system diagnosis is made through the diagnostic connector, using the appropriate diagnostic computer. Primary circuit tests are made at (D1-2) B+ after ignition; tachometer voltage is at D1-1 ; vehicle ground is at D1-3 .

Secondary System
  1. Remove the center wire from the distributor cap.
  3. Using insulated pliers, hold the terminal end about 1 / 2 in. (13mm) from the engine head and crank the engine.
  5. If a spark jumps from the wire to the head, reconnect the distributor wire, then disengage a wire from one of the spark plugs.
  7. Make a metal extension to insert in the spark plug wire boot, then, holding the wire and extension about 1 / 2 in. (13mm) from the head, crank the engine.
    1. If a spark occurs, check ECU sensors using tester MS 1700, or equivalent. If the sensors check out okay, the problem is probably in the fuel system.
    3. If no spark occurs, The rotor, distributor cap or spark plug wires are defective.