Adjust Throttle Position Sensor (TPS)

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Well, if you're here, you are probably experiencing some trouble because the TPS is not a regular maintenance item! Unfortunately TPS failure seems rather common. It's happened to me, and I see it in one to two other Maxima enthusiasts a year. Heck when Edmunds.com was evaluating the new 2K Max, they had problems with the TPS. And the car was brand-spankin new!

 

WHAT IS THE TPS?
The throttle position sensor is a potentiometer - a variable resistor. The ECU sends the TPS a 5V signal. Depending on the position of the throttle, the TPS will send back to the ECU a voltage proportional to how open the throttle is.


Here is a pic of the TPS.


This is the back. Notice the metal bracket that connects to the throttle body. This bracket is rotated by the throttle to change the TPS's internal resistance.

Symptoms:/b> The most obvious is if the TPS just up and dies. You'll get a check engine light and the 0403 trouble code. (Trouble codes will be covered at a later date). However, if the TPS is still gasping its last few breaths, you won't necessarily get the light. But you will get inexplicable, "spontaneous" drops in RPMs. It's most pronounced when you are at idle or the engine is coasting to idle after disengaging the clutch. I have yet to see someone tell of problems when the car was moving/accelerating.

TROUBLESHOOTING::

Here is the TPS in the engine bay (red arrow).

You want to pull out the connector away from you (yellow arrow).
Do this when the engine is OFF.

You will then expose the pins on the connector.

1. Connect the positive lead of your multimeter (voltage checker) to pin 1.
2. Then connect the negative lead to a ground in the engine bay.
3. Turn your key to the ON position (Do NOT start the car)
4. You should see about 5 volts on the multimeter, indicating the ECU is sending the proper signal.

5. Reconnect the harness to the TPS and start the car.
6. Warm up the car. (This is because heat affects resistance)
7. When warm, turn the engine off, and put the ignition switch to OFF.
8. Connect your meter to pins 2 & 3.
9. With the throttle completely closed (foot off the gas pedal), you should read about 500 ohms of resistance.
10. Start pushing on the gas pedal - resistance should rise. When the gas is fully depressed (wide open throttle), the resistance should be about 4000 ohms.
11. If you are slightly off, you can still adjust the TPS to compensate.

12. Notice that the holes that the screws go into on the TPS are slotted, giving you some clearance. Loosen the screws so that you can turn the TPS in place. If you can twist the TPS so that the values are correct for the different throttle positions, retighten the screws - you're done.
13. Otherwise, you are out of luck. Time to pick up a new TPS.

A new TPS will cost about $60-$70. Just unscrew the two screws holding the old TPS and put the new one in and adjust until the resistances are right. Then, tighten down the screws. (Yes, the 2nd screw on the other side not shown in the pic is a pain to unscrew) (And yes, these are not the OEM screws. I galled the OEM screws unscrewing them out. These screws are bought from "Home Depot Motorsports" hehe.

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