TEST 2: Verifying Throttle Position Sensor Has Power
In this test step, we're gonna' make sure that the throttle position sensor (TPS) is being fed with power. If the TPS doesn't have power, it's not gonna' create a throttle angle voltage signal.
This power comes from the PCM and is in the form of 5 Volts DC (also known as the 5 Volt Reference voltage). The wire that connects to the pin labeled with the #1 is the one that supplies this voltage.
Alight, these are the test steps:
Place your multimeter's dial in Volts DC mode and turn the key on but don't start the engine.
This will power up the TP sensor's connector.
Check the TPS connector terminal that corresponds to pin #1, of the TPS, with the red multimeter test lead.
IMPORTANT Be careful when probing the metal terminal of the TPS connector. Damaging the terminal will require that you replace the connector.
Connect the black multimeter test lead to a good and clean Ground point on the engine or directly on the negative (-) battery terminal.
When you've set up the test, have a helper turn the Key On Engine Off (KOEO).
Your multimeter should display 4.5 to 5 Volts on its screen.
Let's find out what your test result means:
CASE 1: The multimeter registered 4.5 to 5 Volts. So far so good since this tells you that the throttle position sensor (TPS) is getting power from the powertrain control module (PCM).
The next and last test, is to make sure that the throttle position sensor is getting Ground (from the PCM too). For this test, go to: TEST 3: Verifying Throttle Position Sensor Has Ground.
CASE 2: Multimeter DID NOT register 4.5 to 5 Volts. Double check all of your connections and repeat the test. If your multimeter still doesn't register the 4.5 to 5 Volts DC...
, then this test result tells you that the TPS itself is not at fault (and thus causing the TPS trouble code). Without power, the TPS can't create a throttle angle voltage signal. Although beyond the scope of this tutorial, your next step is to diagnose and restore this missing power.
TEST 3: Verifying Throttle Position Sensor Has Ground
The throttle position sensor connector wire that feeds the sensor with Ground is the one that connects to pin #3 (in the illustration above).
We'll do a simple multimeter voltage test to find out if the wire is supplying ground or not.
OK, here are the test steps:
With your multimeter still in Volts DC mode from TEST 2.
Probe the TPS connector wire that connects to the TP sensor's pin #3 with the black multimeter test lead. The TP sensor connector can be connected or not to the sensor.
Be careful not to damage the terminal if you probe it on the front of the connector.
Now, with the red multimeter test lead, probe the battery positive (+) terminal.
Once again, when everything is ready, have your helper turn the Key to its ON position but don't start the engine.
If this circuit is OK and the PCM is providing a good path to Ground, your multimeter will display 11 to 12 Volts.
Let's examine your multimeter test result:
CASE 1: The multimeter showed 11 to 12 Volts. This confirms that the PCM and the wire/circuit (that supply this Ground) are OK.
All three test have confirmed that:
- The TP sensor is not providing a varying voltage signal when manually opening the throttle plate.
- The TP sensor is being fed 5 Volts DC.
- The TP sensor is being fed ground.
Therefore, you can conclude that the throttle position sensor is bad and needs to be replaced (and that this will solve the TP sensor code lighting up the check engine light).
CASE 2: Multimeter DID NOT show 11 to 12 Volts. Double check that you're testing the correct TP sensor harness terminal wire and repeat the test. If your multimeter still doesn't show the indicated voltage...
...then we can conclude that there's an open in the wire between the TP sensor harness connector and the PCM's harness connector. In the extreme of cases, the PCM has an internal problem (although this is very rare).
Although testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your 2.4L Nissan Pick Up (Frontier or XTerra) as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).