Testing Ford Sensors Part 3

Throttle Position Sensor (TPS) TESTING:
1. Disconnect the negative battery cable.
2. Disengage the wiring harness connector from the TP sensor.
Using a Digital Volt-Ohmmeter (DVOM) set on ohmmeter function, probe the terminals, which correspond to the Brown/White and the Gray/White connector wires, on the TP sensor. Do not measure the wiring harness connector terminals, rather the terminals on the sensor itself.
3. Slowly rotate the throttle shaft and monitor the ohmmeter for a continuous, steady change in resistance. Any sudden jumps, or irregularities (such as jumping back and forth) in resistance indicates a malfunctioning sensor.
4. Reconnect the negative battery cable.
5. Turn the DVOM to the voltmeter setting. WARNING: Ensuring the DVOM is on the voltmeter function is vitally important, because if you measure circuit resistance (ohmmeter function) with the battery cable connected, your DVOM will be destroyed.
6. Detach the wiring harness connector from the PCM (located behind the lower right-hand kick panel in the passengers’ compartment), then install a break-out box (HUH? Yeh Right, I got one of them laying around somewhere’s… Let’s see Hmmmm, I just poked the wires with two pins), between the wiring harness connector and the PCM connector.
7. Turn the ignition switch ON and using the DVOM on voltmeter function, measure the voltage between terminals 89 and 90 of the breakout box. The specification is 0.9 volts.
8. If the voltage is outside the standard value or if it does not change smoothly, inspect the circuit wiring and/or replace the TP sensor.


Throttle Position Sensor


Throttle Position Sensor




CMP TESTING: Three Wire Sensors:


With the ignition OFF, disconnect the CMP sensor. With the ignition ON and the engine OFF, measure the voltage between sensor harness connector VPWR and PWR GND terminals (refer to the accompanying illustration). If the reading is greater than 10.5 volts, the power circuit to the sensor is okay.
1. With the ignition OFF, install break-out box (2 straight pins in the wires) between the CMP sensor and the PCM.
Using a Digital Volt-Ohmmeter (DVOM) set to the voltage function (scale set to monitor less than 5 volts), measure voltage between break-out box terminals 24 and 40 with the engine running at varying RPM.
If the voltage reading varies more than 0.1 volt, the sensor is okay.

Fig. 1: CMP sensor wire harness connections for the 3-wire sensor

3 Wire CMP Sensor


3 Wire CMP Sensor


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