M35 Stagea P0121 Throttle Problem

[ONCE-NA]

So i've been having having problems with the car going into limp mode intermittently for a couple of months, some days its really bad and sometimes it wont do it for a week at a time.

My mrs drives it mainly, -taking kids to school etc and its really starting to shit her, and thus it impacts on me.

Since it started happening i've swapped out the pedal tps, the throttle body, (both with known working ones) put a new battery in and wiggled and unplugged shit etc, dit the pedal poition and throttle body relearn stuff, but still get the same problem.

I've searched a lot and it seems to be a common problem but had anyone found a definitive fix?

Oh yeah I've also cleared the drain hole under the battery and dried out all the stuff, (fuse box etc around there)

-Rod

[joshm35]

The throttle is electronic so it sounds like you need to do a trottle relearn.

[ONCE-NA]

Yeah I tried that, I've just been looking at an infiniti G35 manual and the throttle circuit diagram, so i'll check some more stuff out tomorrow...

[scotty nm35]

So you have a TPS fault, something is wrong with the tps signal back to the ecu. There are two tps signals and they are both monitored/compared by the ecu constantly and anything that may throw the voltages out, even slightly will trigger the limp mode.

Do you have anything else hanging off the TPS wires? Such as a cruise control, piggyback ecu or something else aftermarket?

[ONCE-NA]

It's got oem cruise?

[ONCE-NA]

Also how do you lift this out? I'm going to check it all for corrosion and swap out the throttle control motor relay at least

[ONCE-NA]

And should one of those relays chatter when you key-on?

It's our second M35 and I don't remember the old one doing it...

Edited May 30, 2015 by ONCE-NA

[ONCE-NA]

2 days and no problems, -looks like I may have been the relay...

[Daleo]

Nicely done; good on you for coming back and letting us know the end result.

[scotty nm35]

If the relay was the issue I can only assume you had water filling the battery compartment, make sure you push the rubber bung out of the bottom so it doesn't happen again.

[ONCE-NA]

Yeah I punched out the drain tube.

However the error occurred 3 times again today.

After being good for a few days. I don't know what to do now!

I've got a whole other car for parts so I might just keep swapping things. Starting with that whole fuse box, and maybe the ecu.

[ONCE-NA]

My mrs said it seems to rev up more than it should just before it throws the error. And it's always after stopping at an intersection or something and when she gets back on the accelerator it does it.

It sounds like a problem with the throttle potentiometer going high or low just off closed but it's been swapped with one from the other car that was fine

[ONCE-NA]

And the problem is so intermittent that it's hard to diagnose

[ONCE-NA]

It appears to be worse when it's cold.

Has anyone who has had this problem ever solved it, lots of searching and I've only found posts with no answers

[scotty nm35]

Plenty of times, either the throttle resistor on the back of the pedal, or the throttle itself is likely the issue, unless you have a wiring fault between them and the ecu.

What codes are the ecu throwing? Is it only the P0121? That seems to relate to the pedal sensor.

When the throttle goes into limp mode it almost disables the throttle. It will sit on 1200 revs, enough to drive out of problems and get off the road. You can actually get more throttle out of it if you push the pedal all the way to the floor, but it is quite dangerous, especially as it happens randomly.

[ONCE-NA]

Yeah that's the only code, and having tried the pedal assembly and throttle body from the other car that never had a problem I'm suspecting a wiring issue, corrosion, dry joint, or ecu problem, I'll swap the ecu and fuse box out over the weekend and pray that fixes it. It was strange that it worked flawlessly for 3 days after changing the relay so maybe there is a wiring problem in the fuse box.

What locally sold car has the same throttle pot? I vaguely remember reading it was a Maxima but can't find it again...

[scotty nm35]

Probably a few cars, but make sure the p/n is the same. Try Amayama, Nissan will sting you hard for the pedal sensor.