Jeep Wrangler/YJ 1987-1995 Repair Guide

Electronic Control Unit (ECU)


The Electronic Control Unit (ECU) is a sealed microprocessor unit located above the accelerator pedal under the instrument panel or below the glove box, next to the fuse panel, and is the heart of the electronic engine control system. The throttle position sensor (or wide open throttle switch) is mounted on the throttle body assembly and provides the ECU with an input signal of up to 5 volts to indicate throttle position. At minimum throttle opening (idle speed), a signal input of approximately one volt is transmitted to the ECU. As the throttle opening increases, the signal voltage to the ECU increases.