Jeep Wrangler/YJ 1987-1995 Repair Guide

Closed Throttle (Idle) Switch



See Figure 1

It is important that all testing be done with the Idle Speed Actuator (ISA) motor plunger in the fully extended position, as it would be after normal engine shutdown. If it is necessary to extend the ISA motor plunger to test the switch, an ISA motor failure can be suspected.

  1. With the ignition switch ON , test the switch voltage at the diagnostic connector terminals D2-13 (+) and D2-7 (-). The voltage should be close to zero at closed throttle and greater than 2 volts when off the closed throttle position.

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Fig. Fig. 1: Closed throttle (idle) switch test

  1. If the voltage is always zero, test for a short circuit to ground in the wire harness or switch, or for an open circuit between ECU connector terminal 25 and the switch.
  3. If the voltage is always more than 2 volts, test for an open circuit in the wire harness between the ECU and the switch connector, and between the switch connector and ground. Repair or replace the wire harness as necessary.