TEST 2: Verifying Throttle Position Sensor Has 5 Volts And Ground
If your TP sensor test results in TEST 1 indicated a TPS voltage signal that DID NOT increase/decrease when opening/closing the throttle plate, then the next step is to verify that it's being fed 5 Volts and ground.
In this section we'll verify that the power and Ground are being fed to the TP sensor by the fuel injection computer.
The red (RED) wire, of the engine wiring harness brown connector, is the one that supplies 5 Volts to the sensor. The black (BLK) wire, of the engine wiring harness brown connector, is the one that supplies the ground.
IMPORTANT: The PCM is the one that feeds this Ground to the throttle position sensor (TPS). Be careful and don't short this wire to battery voltage or you'll fry the PCM.
With your multimeter in Volts DC mode, this is what you need to do:
Verify that the RED wire has voltage ( 4.5 to 5 Volts DC ) with the key on but engine off.
Connect the red multimeter test lead (using the appropriate tool) to RED wire. Connect the black multimeter test lead to the negative battery terminal.
Your multimeter should read 4.5 to 5 Volts DC.
Verify that the BLK wire has Ground with the key on but engine off.
Connect the black multimeter test lead (using the appropriate tool) to BLK wire. Connect the red multimeter test lead to the battery positive (+) terminal.
Your multimeter should read 12 Volts DC.
Let's take a look at what your test results mean:
CASE 1: The multimeter confirms you have power and Ground. This is good since you can rule out electrical wiring issues as behind the cause of the TPS trouble code lighting up the check engine light on your 1.8L Nissan Sentra.
Taking into account the outcome of TEST 1 (where you confirmed that the TPS voltage signal IS NOT increasing/decreasing while opening/closing the throttle plate) and that it's getting power (5 Volts) and ground, then you can conclude that the TP sensor is defective. You can replace it knowing that this will solve the problem.
CASE 2: Multimeter confirms that power or Ground are missing. 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 voltages, 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 1.8L Nissan Sentra as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).
More 1.8L Nissan Tutorials
You can find a complete list of tutorials for you Nissan 1.8L equipped car here: Nissan 1.8L Index Of Articles.
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Ignition COP Coils (Nissan 1.8L).
- How To Test The Starter Motor (Nissan 1.6L, 1.8L).
- How To Test Engine Compression (Nissan 1.8L).
- How To Test The 2000-2002 Nissan Sentra 1.8L MAF Sensor (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!