I've dealt with a TPS voltage problem for the better part of 3 years. I even have 2-3 threads on here. But I keep coming back to the same stupid issue.

So, here is what I've dealt with and the history (over two different H/C setups):

Everything will be okay with the car and then boom... it won't go into idle routines. When I check my TPS, I'm usually seeing 1.6% or more even with TPS resets. The voltage usually is .71V or more but sometimes it's less. So it's frustrating when the TPS voltage is off and that throws off the idle routines and throttle followers. Car can idle without the nannies, but it's not as happy. Also, the follower always being engaged makes deceleration a little jumpy as the IAC opens too much from thinking the throttle is open.

So it makes for a pain in the *** driving around town and coming to stops or driving in parking lots. Otherwise, the car is fine. But when the TPS behaves, the car drives fine!

I have a new PCM on the way to see if it solves anything... I'm thinking the PWM driver in the PCM has gone bad. In the past, it has showed 6V for the 5V reference lead (gray wire) when it went flaky. Today, it was showing 5V... but it was still showing the TPS at 1.6% no matter what. TPS reset. Complete rewrite of the PCM. Nothing. Always showed 1.6% and .71V. When I set the TB, I set it at .59V and tuned it there. When I closed it down to .59V today, it killed the car. It sounded like it was breathing through a straw and my IAC counts went from 40 to 140 trying to keep the car alive. So, I know it's an electrical problem.

I've tried 5 different TPS sensors. And 4 different IACs.

I've also traced the wiring harness to the ABS... I removed the ABS. That solved the problem for a while. Then it reared its head again. And the ECT sensor is on that same PWM from what I can tell. And I'll notice the TPS acting shitty... the ECT goes from 190 to 205 for no real reason. Sometimes when I check, it's 6V reference. Sometimes it's 5V. It doesn't make sense.

In the past when it has happened, I've noticed my battery showing 11.8V... it's an Odyssey AGM battery. I have an AGM charger. I charged it and it won't go above 12.43V... fully charged for the battery is 12.8. So it's pretty much completely discharged right now but still will fire the car no problem. But before when it's been low, the TPS goes flaky. The other sensors all seem to work. But the TPS and ECT both act up. It reads 14.3-14.7 with the car on, so it shouldn't seem like it's an issue... but it is.

Do I have two problems here? The PWM is going out in the PCM and the battery dying?

I want to quit spending money on this problem. The sensors are expensive. The batteries are expensive.

What could be causing the TPS to read high randomly (sometimes it goes away on its own - sometimes, like now, it's been like this for a few weeks and makes it very tiresome to drive).

 

I would look at the battery first, and the alternator as well. You could be getting unconditioned voltage from the alt causing issues as well, or low current output, or low voltage output. Just because you have 12v or 14v doesnt mean you have the right amount of current and also doesnt mean the rectifier bridge is working correctly.
Also check and upgrade the exciter wire on the alt. It can cause issues as well.
Then go to comp.
If the charging system isnt verified as working well it wont matter what computer you use.

 

I just put a new AC Delco 145A on there. The exciter wire I redid when I first got the car as it was trashed.

But the battery has been the culprit before. I'm going to go ahead and try a new PCM and a new battery. The PCM shouldn't be that flaky...

Btw, when I check KOEO I always ground back to the battery first.

 

Sometimes the internal comp ground can mess up also. Ive seen it more on trucks though. Still get the alt checked to make sure the diodes are good and cables are tight. free and easy to do. The alt grounds through the case so if your engine grounds are loose it an cause issues also.
If you want some more info on the grounds etc i can email then to you.
A friend with a shop had an issue on a maggied ls6 swapped 04 1500 4x4. Had the torque rush tb adapter to use the ls2 tb on it. It had all sorts of odd issues related to the tac module. But it would act up worse when the fans came on....efan conversion also. So after finding some frayed wires it would still got into REP and kill throttle and act up. Turns out the 2yr old alt was to blame and it also killed the battery as well.
Just shows you how important a good charging system is, but also how it affects so much.

 

Yeah. This started well before I swapped the alternator, but yeah, it's still going.

I think a new battery to go with the new alternator may be in order.

 

Just picked up an Optima Yellow Top. Everything's fine now.

Also have a new PCM on the way as well from Frost to have on hand if this comes up again. It seems like whenever the battery resting voltage is around 12.2V or so, the TPS goes apeshit. Even if the charging system shows 14.7V at the battery with the car on. It's like the battery is unable to regulate and smooth out the flutter of the alternator if it's half gone.

 

Hi i got a problem too with my tps on my 5.3 swap mi tps does not let my tranny shift correct it accelerate perfect in idle but when i put in gear it does not shift untill get on 6000 rpm