How To Test The Throttle Position Sensor (2.4L Mitsubishi)

TEST 2: Testing The Sensor Return (Ground) Circuit

As you saw, testing for power was easy enough. Testing the Ground circuit is easy too since we'll perform the same multimeter voltage test on the Ground wire.

The wire that feeds the TPS sensor with Ground is the one labeled with the number 3 in the photo above.

Here's what you'll need to do:

1. Place your multimeter in Volts DC mode.
2. Probe the circuit labeled with the number 3 in the photo, with the black multimeter test lead.
3. The red multimeter test lead goes to the battery positive (+) terminal.
4. Turn the key to its ON position but don't start the engine.
5. The multimeter should display 11 to 12 Volts..

Let's see what your test results mean:

CASE 1: The multimeter displayed 10 to 12 Volts. This is the correct test result. You can conclude that the fuel injection computer is feeding Ground to the throttle position sensor.

The next step is to check that the TP sensor is creating a good throttle position signal the PCM can use, go to: TEST 3: Testing The TP Signal.

CASE 2: The multimeter DID NOT display 10 to 12 Volts. Without Ground the TPS won't work.

This is usually happens when the PCM is NOT supplying a Ground either because of an internal fault/problem or there's an open in the wire between the TPS and the PCM itself. Altho' testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your Mitsubishi vehicle as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TEST 3: Testing The TP Signal

OK, we've come to the test that'll let you know if the TPS is bad or not. Before you start, the engine has to be at its normal operating temperature. So, if the engine is cold, start 'er up and warm her up.

You'll need a helper to assist you in this test step, since he or she will need to lightly tap on the throttle position sensor's body with a screw driver (or other appropriate tool) while you observe the multimeter and manually actuate the throttle. OK, let's start testing:

PART 1

1. Select Volts DC mode on your multimeter.
2. Probe the circuit labeled with the number 2 in the photo with the red multimeter test lead, using an appropriate tool to pierce the wire.
3. Ground the black multimeter test lead directly on the battery negative (-) terminal.
4. Turn the Key On with the engine Off.
5. Your multimeter should register about 0.6 Volts DC.

PART 2

6. Now that the multimeter is set up...
7. Manually rotate the throttle plate by hand as you eye-ball the multimeter's voltage readings.
8. The multimeter's initial voltage reading should increase smoothly as you open the throttle plate to its Wide Open Position. At Wide Open throttle, your multimeter should register 4.9 Volts DC.
9. Now, slowly release the throttle plate to its fully closed position, all the while observing the multimeter's reading.
10. The multimeter's voltage reading should decrease in a smooth and linear fashion and return to the voltage you observed in step 5 (about 0.6 Volts DC).

PART 3

11. OK, now have your helper lightly tap the TP sensor with the butt of a screw-driver's handle (or something similar).
12. As he or she taps, you need to slowly and smoothly open the throttle to its Wide Open position and then slowly release it back to its closed position.
13. All the while you've got your eyes glued on the multimeter to see if the tapping affects the voltage readings.
14. Repeat this (tapping the throttle position sensor) several times to make sure of your results.

Let's take a look at what your test results mean:

If the throttle position sensor (TPS) is working correctly, the multimeter will register a smooth increase in the DC voltage until the maximum voltage is reached, which is about 4.5 Volts DC. Then, as you slowly release the throttle plate back to its closed position, the multimeter will display a gradual decrease in voltage till the initial base voltage is achieved (which you recorded in the beginning of the test).

If the TPS is bad, then there will be sudden gaps/loss of voltage or the voltage reading will jump around crazily as you increase or decrease the throttle plate's to its fully open or fully closed position, especially when you tap on the sensor. Or, there will be no voltage reading at all. OK then, here are the two possible outcomes:

CASE 1: The multimeter registered a smooth increase or decrease in voltage. This is the correct test result.

You can conclude that the throttle position sensor is good and not the cause of the TPS fault code issue. Go to: TEST 4: TPS Code Won't Go Away for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: The multimeter DID NOT register a smooth increase or decrease in voltage. With this test result you can conclude that the throttle position sensor (TPS) is bad. Replacing the throttle position sensor will solve the TPS diagnostic trouble code (DTC) lighting up your check engine light (CEL) on your Mitsubishi (or Chrysler Sebring or Dodge Stratus) vehicle.

TEST 4: TPS Code Won't Go Away

So you've tested the TPS per the instructions in this article and according to the test results, the TPS is good yet the check engine light is still on. Well, here are a couple of suggestions that might inspire your next diagnostic move:

1. The throttle plate's idle-stop screw's factory adjustment has been altered so that the engine could be idled up and mask a miss/misfire and/or rough idle. This increases the TP sensor's signal to the PCM. The PCM doesn't like it and lights up the check engine light (CEL).
2. The throttle cable is binding and causing the throttle plate to not fully close.
   • This can be verified by simply having someone inside the vehicle pushing the accelerator cable to the floor and releasing it, with the engine OFF, while you visually check that the throttle plate and cable are not getting stuck somewhere in their travel.
3. The TPS is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
   • I have found that the best way to test these intermittent problems is to road-test the vehicle with the multimeter hooked up to the TP signal wire with a long wire so that I can comfortably observe the signal going up and down as I or someone else drives.
4. The TP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.