TEST 2: Checking Throttle Position Sensor (TPS) Power And Ground

Checking Throttle Position Sensor (TPS) Is Getting Power And Ground. How To Test The Throttle Position Sensor (TPS) -2.3L Ford

If in TEST 1, your multimeter did not register an increasing (or decreasing) voltage as you manually opened and closed the throttle plate on your 2.3L Ford Ranger (Mazda B2300)...

... Then there's a good chance that the TP sensor is NOT getting either power or ground.

As mentioned earlier, power comes in the form of 5 volts DC and is provided by terminal number 1 of the TP sensor harness connector (the Brown w/ White stripe wire connects to terminal number 1).

ground is provided by the PCM thru' terminal number 3 of the TP sensor harness connector (the Gray w/ White stripe wire is the one that connects to terminal number 3).

NOTE: It's never a good idea to probe the front of the terminal of the harness connector or you run the risk of damaging the metal terminal. What you should do is backprobe the connector or use a wire piercing-probe to check the wire itself.

With the multimeter if Volts DC mode, this is what you need to do:

  1. 1

    Check terminal #1 for power with the Key On Engine Off (KOEO) (see illustration 1 of 3).

    Connect your multimeter's red test lead to terminal #1 and the black lead to the battery negative (-) post.

    The Brown w/ White stripe wire connects to terminal number 1 of the TP sensor harness connector.

    The multimeter should register 4.5 to 5 Volts DC.

  2. 2

    Check terminal #3 for ground with the Key On Engine Off (KOEO) (see illustration 2 of 3).

    Connect your multimeter's black test lead to terminal #3 and the red lead to the battery positive (+) post.

    The Gray w/ Red stripe wire connects to terminal number 3 of the TP sensor harness connector.

    The multimeter should register battery voltage (12+ volts).

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

CASE 1: Both ground and power (5 Volts) are present. This is the correct and expected test result.

Since you have now confirmed (in TEST 1) that the TP sensor is not producing a signal and in this test you've confirmed that the sensor is getting both power and ground... you can conclude the TP sensor is bad and needs to be replaced.

CASE 2: Either ground or power ARE NOT present. This test result exonerates the TP sensor as being bad and tells you that the reason the TP sensor is not producing an increasing/decreasing voltage signal in TEST 1 is because it's missing power or ground.

Although it's beyond the scope of this tutorial, you'll need to find out why this signal is missing to get the TP sensor back on the job.

Throttle Position Sensor (TPS) Is Good But Code Won't Go Away

There are quite a few things that can fool your 2.3L Ford Ranger's fuel injection computer into thinking the TPS is bad (when it really isn't).

So if you have already replaced it (or tested it) and the TPS trouble code keeps coming back, this section may be of help.

Since you've already eliminated the TP sensor as the source of the problem (trouble code) itself. Your next steps should be:

  1. Checking the adjustment of the throttle plate stop set screw.
    1. This screw's adjustment usually has been altered to idle up the engine and mask a rough idle condition. The PCM doesn't like it when this is done and sets a TP sensor code.
  2. Check the continuity of the TP sensor's wires (between the PCM and the TP sensor connector).
    1. If there's a break in any of the 3 wires, the PCM will set a TP sensor code.
  3. Check for a bad fuel injection computer (PCM).
    1. Is there a way to test for a bad PCM? Yes and no. The only way to test for a bad PCM is to test it indirectly. This is what I do to test for a bad PCM (with about a 98% success rate):
      1. Eliminate the TP sensor itself as bad.
      2. Check the continuity of the 3 TP sensor wires (between the PCM and the sensor). The idea here is to make that none of the TP sensor wires are cut (‘open’).
      3. Check all of the PCM ground wires by doing a voltage drop test on them. This simply involves checking the ground wire for voltage (not Ohms) with the Key On Engine Off. There should be no voltage on the wire. If there's voltage (2 Volts or more) that specific ground wire is not providing a good path to ground and it means you need to clean the ground terminals and/or check their condition.
      4. Check that the PCM is getting power on the all of it's power circuits.
      5. After eliminating the TP sensor, a problem in the 3 TP sensor wires (between the PCM and sensor), eliminating the PCM's ground wires, and verifying the PCM is getting power on all its power circuits... then, and only then I can say with confidence that the PCM is bad.

The key to testing all of the above (and either exonerating or blaming the PCM as bad) requires that you have the specific wiring diagram for your particular Ford vehicle.