Mercury F4SZ-9B989-A Engine Throttle Potentiometer

Before deciding that sensor failure has occurred, it is necessary to inspect wiring problems when troubleshooting the Throttle Position Sensor (TPS). The TPS is a potentiometer on the throttle body that sends throttle position to the PCM through a voltage signal. Surging or stalling may result from a faulty TPS. To test the TPS, disconnect the sensor and check the reference voltage, which should be around 5.0 volts with the ignition On and the engine off. Reconnect the sensor and measure the signal voltage, which should be 0.5 to 1.5 volts at closed throttle and increase steadily to 4.0 to 5.0 volts at wide-open throttle. Ensure that when closed, the meter reads less than 1.5 volts, and when fully open it gives about 5.0 volts reading on the multimeter display. There can be a need for advanced tests if those issues continue happening in your car engine system or have some effect on vehicle performance. Remove the snow shield (on 2001 and later models) to replace the non-adjustable TPS. Then, disconnect the electrical connector before firmly attaching the new sensor on the throttle body.