Throttle position sensor—how to test

[JimBee]

In this recent post, we're shown a series of pictures of a multimeter being used to test the TPS, but I can't see how he hooked up
the test leads.

On my '96, I can't see a way to do that. Help appreciated!

https://www.matthewsvolvosite.com/forums ... 15#p235115

[electech]

These sensors are fairly rugged, not my first suspicion, but here's how to test:

Short answer:
Pin 1: ground reference from ECU - 0V
Pin 2: 5V reference from ECU
Pin 3: Sensor signal, range 0.1V to 4.9V, increasing with throttle opening

Layman's translation:
The TPS has a connector with three pins. For all it's usefulness, VADIS does not have the TPS connector layout and the sensor test procedure for the '96, so I can't tell you which pins do what on your car. On the 98, the center pin is the 5V reference signal, and is white or yellow. The two outside pins are the ground reference (0V) which is brown, and the output signal (0.1 to 4.9V) which is orange with a white stripe. (the '98 mototronic uses a different sensor that runs 0.5V to 4.3V, the '96 voltage specs are 0.1V to 4.9V)

All 3 wires go to the ECU. DO NOT put an ohmmeter on the connector or you risk damage to the ECU. Only use a voltmeter on the ECU side of the connector.

There is one good way and one "other" way to test the sensor. The good way is connected, ignition on, with a voltmeter. You need to access the wires. Dealers use a breakout box at the ECU. The rest of us use back probe pins, open the connector case (if you are comfortable), or do what most DIYers do and shops have to fix: Poke holes in the insulation. (If you do this, ALWAYS repair with silicone. Otherwise we will be frustrated trying to help you find a problem caused by a corroded sensor wire next year.)

With the sensor connected, and access to the wires with your voltmeter, turn on the ignition but do not start the car. Measure the voltage between the center pin and ground. Should be 5.0V +/- 0.5 volts. One of the other wires (ground) should read 0.0 volts, and the the other wire (sensor signal) should read less than 1 volt. If both wires are slightly above 0 volts, go with the wire with the higher voltage. Watch the voltage on this wire as you slowly open the throttle. Pause at at least 2 or 3 places between idle and wide open (like at 25% open, 50% open, 75% open.) Record those voltages if you want. Repeat this test at least 3 times, moving from idle to wide open throttle and back again.

The "other" way to test: Ignition off, disconnect the sensor. On the sensor itself (not the connector wire!!) put the red lead of the ohmmeter on the center pin and the black lead on one of the outside pins. It should read a steady value under 1 ohm. When you rotate the throttle, the value should change. If it reads over 1 ohm, or if the value doesn't change, you have the wrong pin. Keep the red one in the center and check the other outside pin.

(make sure you don't disconnect the sensor with the ignition on or you will set a code and have a CEL)

Now, you know how to hook up the meter. You have to be sure your readings are good...if your probe slips off the wire, you will get faulty readings. What the results mean:

The values are all relative. The exact voltage doesn't matter (0.17V at idle is no better or worse than 0.35V at idle). The only thing that matters is the change. If the sensor shows a nice steady increase in voltage (decrease in resistance) as the throttle is opened, and at idle does not drop below 0.1 volts (or exceed 1 ohm) and at wide open throttle does not exceed 4.9 volts, then the sensor is good. If the sensor "drops out" (goes below 0.05 V or over 1 ohm), it is a "dead spot" and the sensor is faulty. Replace the sensor.