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Questions and Answers

Nissan Maxima Throttle Valve Switch

Q. My 1986 Nissan Maxima needed a new Air Flow Meter which I replaced along with the spark plugs and O2 sensor. The engine had run really rich when the AFM failed. I replaced the O2 sensor because of all the carbon on it. The ECM still says the throttle position switch has failed. I removed it from the throttle body and found that the plug contacts and the plug itself where badly corroded.

Nissan Maxima Throttle Valve Switch

I ended up cutting the harness and installing a new connector to it and soldered the other connector to the existing TPS. The TPS checks out fine with a DVM and I have adjusted it such that the idle contacts just open when the throttle is slightly opened (as per the Haynes manual).

I cleared the computer and drove it and the computer returns the 44 code. I drive it again and the computer returns 23 (TPS failed) and 31 (ECM Load) error codes. The car drives fine at times then it starts to have acceleration stumbling. It always idles fine.

My question is what exactly does the TPS do for the ECM in this particular Nissan Maxima??? Could the switch be failing sometimes which goofs up the ECM?? Do you know which wires in the ECM plugs represent the TPS, so I can double check wire continuity through the wire harness? I don't have a schematic. HELP!!

Sincerely,
Paul

A. The TPS is a potentiometer connected to the throttle valve shaft. As the throttle is moved, the resistance varies, altering input voltage to the ECM. If you had slot cars as a kid the controllers were the same thing as a TPS. The 1986 Nissan Maxima doesn't have a TPS pre se, it is actually a Throttle Valve Switch (TVS). The TVS closes at idle to signal the ECM when the throttle is in the idle position.

There is a 5 volt signal that goes in the center and a set of idle and full throttle contacts. Now , with a volt meter, check for 5V at the center terminal, red wire. Then check for 5V at the green/yellow wire. Now open the throttle and the reading should go to 0V. The full throttle contacts are not used on this application.

If that's okay, check continuity between the green/yellow wire at the throttle switch and pin 18 of the PCM. No continuity means the wire is open. Now check continuity between the red wire at the throttle switch and pin 25 of the PCM. No continuity means the wire is open.

If everything checks out, the PCM is bad.

Nissan Maxima Throttle Valve Switch
Throttle Valve Switch (TVS)

Nissan Maxima Throttle Valve Switch

Additional Information provided courtesy of ALLDATA

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