Mechanics

TPS PERFORMANCE PROBLEM...DTC P0121

Hyundai Other

Well, I'm pretty much at my wits end now because I've thrown a TPS performance code several times. DTC P0121: Throttle Position Circuit Range/Performance Problem, and no matter what I replace in order to fix this it just keeps on happening. My vehicle is a 2003 Hyundai Tiburon with a 2.7 liter, 6-speed with only 29,000 miles that is also supercharged (aftermarket parts). As for what the car is doing. That's the crazy part. I can ONLY recreate the problem on the highway, and I must drive at least 30 - 45 minutes straight (normal driving - no boost) before it will start acting up. When the problem occurs, the car will just feel like it loses all acceleration (just like hitting the rev limiter), and then after a couple of seconds pass, the car kicks back to life and runs perfectly again. This will just keep cycling over and over again. And you can see the voltage drop on the TPS (with the mafterburner software) during this whole ordeal. Now, the crazy part about this is that, in order to fix this temporarily, all that I have to do is reset the ECM by pulling the fuses for a few minutes. After I do this, the car will run great and it will take another long drive to get it to act up again.

Here is a list of things I have tried since throwing this code. I have done the following:
1. Ran multiple ground checks on all my wires
2. Replaced the TPS with a brand new Hyundai OEM sensor
3. Redid the splice connection for my TPS on my Mafterburner (fuel tuner)
4. Replaced the ECU with a known good one.
5. Cleaned MAF sensor - didn't do anything for me.
6. Replaced MAF sensor with Hyundai OEM sensor.

The only two sensors that I can think of that would possibly cause this to happen would be either the ECT or IAT sensors, but I'm not even 100% sure of that.

So if you could please try and push me in the right direction, I would greatly appreciate it.

Thanks!
Avatar
Macatron
January 14, 2007.



You did the supercharge installation? And how many miles ago was that installed?

Bruce Hunt
Jan 14, 2007.
Yep, my roommate and I did the supercharger install ourselves. We're both gear heads, and we've installed many aftermarket parts on various vehicles. As for mileage. It was about 3,000 miles ago.

Thanks for replying!

Tiny
Macatron
Jan 15, 2007.
During this issue you get no check engine light and that is still functioning, right? When you say no boost you mean the supercharger is not engaged? Is there a means to by pass or go back to prior supercharge and test the unit?

Bruce Hunt
Jan 15, 2007.
Well, the CEL doesn't initially come on. It takes a second drive cycle in order for it to throw. So, in other words, if I shut the vehicle off when it is acting up, and then start it again without pulling the ECU fuses it will throw the TPS performance code. But, being that I already know what code it's going to throw and how to temporarily fix it it (pulling the fuses), I don't bother letting it throw the code any more.

As for the supercharger not making any boost, I'm reffering to normal highway driving. The boost gauge is either reading zero psi or 10 to 20 inches of vacuum (due to it being a roots or eaten type of blower). I usually drive around 75-80mph on the highway in 6th gear turning about 3,500 RPMs.

Well, it would be a major undertaking to convert the vehicle back over the the factory manifold again, just to give it a try, so I'm hoping for another alternative at this moment and time.

I did notice that the Intake Air Temperature (IAT) was very oily when I reinstalled it during the blower installation, so I cleaned it with some brake cleaner. I didn't figure that this would be a problem, but I could be wrong.

So, with that said, do you think that the IAT is possibly the issue here? Or could it even be an Engine Coolant Temperature sensor (ECT)?

Thanks, and let me know if you need any further information.

Tiny
Macatron
Jan 15, 2007.
Any updates? Thanks!

Tiny
Macatron
Jan 16, 2007.
What I am wondering is does the documentation for the supercharger make any recommendations of sensor updates or have a troubleshooting section. You have changed the air flow in the engine and somehow the engine does not seem to be able to handle in over the long haul and stumbles. You replace with OEM but isn't it possible that it needs to be replaced with other than OEM? Anyone else on the forum got a view or idea on this?

Bruce Hunt
Jan 16, 2007.