Code 31: Not getting any power to the TPS - SOLVED

[georryan]

So after rewiring the ecu harness to make it adaptable to an EJ20G, I took the car for a spin and when I had the pedal floored and was hitting full boost (about 10 psi right now), the engine would stumble. When it stumbled I'd get a flicker of a check engine light.

So I pulled the codes I got a code 31 (Throttle position sensor).

I hooked up a multimeter with the ignition turned on and didn't get any readings. I then decided to just see if a test light would light up. I tested to make sure the test light worked, and it did, and then tried each of the pins in the B58 connector. I think the TPS is supposed to be found in pin 1,2,3 (1-ground:white, 2 -signal:black, 3-power:red). I can't get my test light to get any light whatsoever on any of those pins let alone any pin from the B58 connector. The test procedure and adjustment procedure seems to indicate that there should be some readings coming out of there.

I also tested the pins on the TPS itself after removing the connector for the harness, and tried to see if I got anything from there. Nothing.

Is my TPS thoroughly shot, or am I completely missing something? Can anyone confirm that I'm doing this right?

-Ryan

[georryan]

Oh, and something else....

When the car is running there is no check engine line on. Car runs fine until I push it enough to get full boost, and it doesn't seem to stumble until right at full boost.

[dscoobydoo]

This sounds stupid, but go back and re-check the ECU like you were starting from scratch BEFORE you modded to the 20G. Guessing you did a little something.

[Legacy777]

I'm not really following what you "modified" in regards to the TPS. Can you elaborate?

Also, I don't really follow your testing procedures. You can measure voltage on the power source for the TPS at the ECU with a multimeter. It may not work with a test light since the voltage is only 5v. For the rest of the testing, I'd really just suggest checking the wiring from the ECU to the TPS to ensure it's good. From there, do all the checks from the FSM associated with checking just the TPS.

[georryan]

Turns out my multimeter has a short in it, and it isn't working properly. I should have a new one this weekend.

[georryan]

I picked up a new multimeter, and measured the resistance across the terminals in the TPS, and its bad I believe. It does measure 0.5V at fully closed, but fully open it considerably higher than 5V. I couldn't adust it enough to get it in the right range, so that's probably all there is to the problem.

-Ryan

[Legacy777]

In my opinion the actual voltage isn't that important. The reason being is because every ECU will have a slightly different 5v reference voltage. Some may be a little higher, some may be a little lower.

As long as the resistance of the TPS checks out ok, that should be more important.

[georryan]

I ended up grabbing 3 different throttle position sensors from a junk yard and tried to find one that would be close to the right resistance. The best one had a resistance of 11 kOhms instead of 12, but I put it in and adjusted it as close to the FSM spec as I could. That seemed to help slightly, but I was still getting stuttering, but without the check engine light. The next thing I did was rush out to get new spark plugs.

I picked up a set of NGK BKR6E plugs and gapped them to .030 and that did the trick.

Car runs smooth and strong at this point. The boost is only set to 10 psi, but now I feel safe enough to start playing with that. I just need to set up a meter to watch the MAF and the air/fuel ratio.

-Ryan

[Legacy777]

Glad to hear you got it solved. How old are your spark plug wires?

[joelegacy]

what tps's did you pick up at the junkyard? im looking for a quick cheap replacement for my 91turbo

thanks for any info