The throttle position sensor in your Nissan Maxima is made up of two three pin connectors. The Maxima TPS sensor is part of your idle switch and throttle body, and is mounted to the shaft of your throttle. Basically as the main component of your Nissan ECU in relation to your throttle, this sensor relays the exact opening of your throttle blade.
As your Nissan ECU receives this data, it will know how much fuel to deliver as the engine speed increases. Without this data your 3.0 liter Maxima engine will run poorly, and chances are your idle will suffer. When your Maxima TPS sensor starts to go south on you, you’re going to see problems right away. If you suspect your Maxima throttle sensor is the culprit behind your idle issues or your poor throttle response, this DIY testing guide is for you.
Today I’ll be showing you how to test the Maxima TPS Sensor in a 1999 Nissan with a 3.0 liter engine in it. This sensor shares a lot of similarities between the automatic transmission equipped Nissan 240SX. In order to complete this testing tutorial, you will need to use a digital multimeter.
The throttle position sensor is mounted to the opposite side of your throttle body. When the internals of this potentiometer style sensor break, or goes bad it’s going to cause quite a few Nissan Maxima problems, let’s take a look at a few.
Bad Maxima TPS Sensor Symptoms
When this sensor fails your Nissan engine computer will basically be operating blind. These problems will compromise your driveability and can cause long term issues.
- Inconsistent throttle response
- 3.0 liter engine increases speed on it’s own
- Lack of Power
- Maxima won’t idle
- Takes a long time to start
- Check Engine Light ON
If your Nissan Maxima check engine light is on, you’ll need to retrieve the alphanumeric code with a OBDII scan tool. If the stored Diagnostic Trouble Code returns as a throttle position sensor related error like a P0120, then you can use this DIY guide to test your Maxima TPS.
Testing your Maxima TPS Sensor for Power
Insert the Maxima ignition key and turn to the “ON” position. This will power up the sensors in your 3.0 liter Nissan engine bay. Before you can reach your TPS sensor however, you need to disconnect the intake snorkel from your Maxima MAF sensor.
Using a 8mm wrench or a flat head screwdriver, loosen the wormclamps on your intake piping. You can also unclamp the air box to your 3.0 liter Maxima engine, and lift the intake pipe and mass air flow sensor out as a whole.
Now that the intake snorkel has been taken out, you can access the dual connectors of your Maxima TPS sensor.
Don’t forget that there are two three pin connectors, and you’ll be testing the left most harness.
The three pin connector on the left is the one that drives your throttle position to your Nissan engine computer. Refer to our Nissan Maxima TPS sensor wiring diagram below to see how the pins are identified.
Disconnect the throttle sensor harness, and with the key set to the ON position you will be testing the wire that leads to PIN A. Refer to the wiring schematic below to see which wire this should be, but remember that our diagram is showing the SENSOR side of the Maxima TPS.
Gently probe the wire that leads to PIN A, don’t forget that you are testing the ENGINE harness side of the equation.
You should have 5 volts of power at this wire. When using a digital multimeter to test your TPS, never force the leads of the multimeter into the harness. If you do you run the risk of creating connectivity issues that could plague your Nissan with intermittent signal.
Now that you’ve confirmed you have power at this wire, you must check for a ground circuit. To do this you need to put the red lead of your multimeter to the positive battery terminal and probe the wire that goes to PIN C for a ground. If your multimeter shows a 12 volt signal then the wire at PIN C has the proper ground signal.
Testing your Maxima TPS Sensor Signal
If you have power and ground at the throttle sensor, you need to measure the signal wire. As you may have already guessed this wire is the one that leads to PIN B. Reconnect your throttle position sensor first. You will then need to find a way to get contact to the wire that’s coming from PIN B.
You can do this by slicing open the wiring harness, or piercing the wire with the red multimeter lead. Backpinning the wire to PIN B can also work as well, by unbending a paper clip and inserting it into the back of the TPS connector. To do this put the black lead of your multimeter to the negative battery terminal. Using the red lead you can now read the signal voltage to see what your Maxima TPS sensor is sending your engine computer.
You don’t need your engine to be running for this test, just keep your ignition key to the “ON” position. With your throttle completely closed, the TPS signal wire should read between .2 to .9 volts of DC signal.
Now depress the throttle body to open your throttle blade until it hits the backstop. At this position or Wide Open Throttle the signal wire should be sending between 3.8 and 4.5 of DC voltage. The last part of our DIY test is to slowly close the throttle plate. Monitor the voltage and make sure that the voltage scales back to the original value slowly and evenly. There should be no spikes in voltage or gaps in the signal range. Repeat this test by slowly opening and closing the throttle and monitoring the changes in the signal voltage.
If your Maxima TPS sensor does not respond in the proper manner, you’ll need to remove it and install a replacement throttle position sensor. After installing the throttle sensor, you will need the multimeter to “dial in” or calibrate the replacement TPS sensor. Have any questions about our testing guide for your Maxima TPS? Leave us a comment below and let us know!