Throttle position sensors
 

I have been working on a track Z that someone else started and did most
of the work on. The car has had codes P0603 (ECM back up circuit), P0223
(accelerator pedal position sensor 2 / switch B and P0122 (accelerator
position sensor 1 / switch A). The car got an ecutek tune through the previous
owner. One mechanic said not to worry about those codes. The check
engine light would come on and off by itself periodically. Since it is a track
only car I cannot drive it far, unless I'm on a track. Had my first track day
with the car a month ago and had four sessions with no issues, went
back the following day and the car would rev from 800 to 2200 by itself instead
of idling. Called it a day and spent the next couple of weeks prepping and
then painting the car. That issue went away, but I took it in to another
mechanic, who said it would need an ECU update through nissan, but said
the the car could be taken to the track as is. Went to another track weekend
and half way through first session the car went into 5mph limp mode.
Code P2138 (accelerator pedal position sensor circuit range/performance).
Cleared the code, cleaned the MAF sensors. Unplugged the throttle plugs and
sprayed with cleaned and reconnected. Ran a session with no issues. Next
session after two laps check engine light came on, but no driveability issues.
Called it a weekend any way. I've read that it could be a range of issues,
including tire and wheel size. Suggestions as to where to start would be appreciated. I don't want to just start replacing components, such as pedal
assembly, and hope I fix it by sheer luck, since I'll have to go to the track to
test out any of the fixes.

What is your tire sizes?

275-40-18

That is a square set up. As my main tire setup I am planning to go to a
305 660 18 racing slick, which would have a diameter right at 26".

You're good if your tire diameter is within 3% difference from front to to rear diameter. You being squared isn't a problem. So you can rule out the tires.

Have you tried the TPS relearn? Might just be a bad TPB and or throttle pedal. FSM should detail the diagnostics for each.

:iagree: first thing I would have done would be the TPS relearn - it's super easy.

I have a couple of pedal assemblies laying around if you end up needing one. Just PM me.

Thanks,
I'll try that.

After struggling with the electronics and not finding the root cause, took it to
Nissan dealership and they had a mechanic who knows the 370Z very well.
He determined very quickly that the previous owner of the car had removed
some important sensors, including yaw sensor, so ECU was looking for info and
getting nothing in return. He said he was able to change some settings in the ECU, so the computer would not look for info that wasn't forthcoming.
He said I need an aftermarket ECU so I can program the inputs.
He recommended the AEM Infinity, in my Honda S2000 I had the Haltech Elite 2500. Any recommendations?

Only one standalone that works. Motec, it will take 10k to get it up and running.