# Z31 TPS question



## snowraider (Jun 24, 2013)

Hey guys would a bad TPS signal cause my 300 to go into limp mode not running past 2000-2500 rpm? or maybe O2 sensor?


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## rogoman (Dec 16, 2004)

A bad MAF could cause the engine to go into 'limp mode'.


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## snowraider (Jun 24, 2013)

ya i know im getting that code but all the test i have been doing are telling me otherwise and i have also swapped it for 2 other maf's with no change


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## rogoman (Dec 16, 2004)

I don't see an O2 sensor being able to put the engine into limp mode. However a bad TPS could do it. First try unplugging the TPS and drive it; it won't run right but see if it stays out of limp mode.


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## Big Slappy (Aug 1, 2013)

The TPS on a z31 is not like the normal potentiometer on most cars. It is merely an on-off switch, telling the motor when to return to idle to save fuel. I have heard of many people unplugging the TPS to troubleshoot and the car runs almost the same, but I have not confirmed this. 

The O2 sensor does barely anything on these cars. Mine is unplugged, and I have a wideband installed in the O2 bung. It will vary fuel trims if you are getting bad readings from the O2 sensor, but at WOT the ECU is not fast enough to compensate for any oxygen readings anyways. 

95% of the time your problem is caused by a bad MAF sensor. Either way, both of these parts are <20$ at a junkyard, and are very commonly available used on z31performance.com. Check your harness as well, and make sure you are getting good connections.


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## snowraider (Jun 24, 2013)

ya ive replaced the maf and it didn"t change anything and i have done the harness tests and they all come out without any issues


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## smj999smj (Jan 1, 2006)

If you erased MAS code and it reset, if you are confident in your circuit testing and a known good MAS didn't fix the problem, you could have a bad ECM.


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## snowraider (Jun 24, 2013)

ya i have also replaced the ecu aswell haha it could be the harness


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## Big Slappy (Aug 1, 2013)

Try and double check injector wiring and that your battery is in good functioning order, and the connections are good.


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## BeyondBiscuits2 (Jan 18, 2006)

Nissans need three sensors to run properly (before CAN system days); Mass Airflow, Throttle Position, and Coolant Temperature. I've not heard of the latter two causing an engine to go into limp mode, but for sure on the former. I know the cylinder head CTS can cause all sorts of issues, as I experienced them myself on my ZX. More than likely, though, it is your MAF sensor. If you're buying junkyard parts, there may be a good chance they're bad too. After all, most sit out in the elements, and aren't maintained. Also, as previously suggested, erase all the codes on your ECU prior to retesting.


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## snowraider (Jun 24, 2013)

alright and the maf is a new one from thezstore.com so i dont believe its the maf anymore could be the injectors though i have just noticed a leaky one in the front


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## rogoman (Dec 16, 2004)

Make sure the fuel pressure is up to spec; if very low, the FPR or the fuel pump may be bad.


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