Hey guys, been a while since I've been at this section of the boards!

Anyways,
I just took the IROC out of storage for the first time since last fall. She started up right away sounded all healthy. However, after sitting on idle for a little bit, the idle speed started moving up and down, varying from approximately 1500 to 2500, and then I got a code 21. Checked it and found that that indicates a high voltage on the TPS at idle. When I put my VOM on it on the A and B terminals, it reads 4.86V The A - C terminals reads 4.99V
Whats up with that? Did the TPS go bad from it sitting in storage for 4 months?


Ken

 

Ken,

Good to know you're still here.

Your TPS might have failed. Does the voltage vary at all with throttle position?

 

Just to verify that you have a good ground (A terminal) you can measure voltage from B (blue wire) to ground. However, since you are reading the 5VDC between C and A, the wiring is probably O.K.

 

Hey Jeff, whatsup!!

It does vary a little bit with trottle position, to about 4.95V at WOT. I'll check to make sure that the ground is good.

I'll look through my stuff to see if I still have the old TPS that I replaced back when I had those problems a couple of years ago to do some testing with.

The TPS is all closed in, right? There is no way of opening it and clean it?


Ken

 

Yes, the TPS is supposed to be sealed. Moisture and contaminants seem to be able to get in somehow, but I doubt you'll be able to clean it. Your spare may be a good idea, and you don't even have to install it - Just plug it in to the wiring harness and move the small throttle lever to see if it works.

 

Well, seems like I've pitched that old TPS... So, Im going to pick one up at a US car parts place that is on my way when Im headed away for easter. I check with them and they have one(!) in stock for $120 (d@mn I miss the US sometimes! )
Picking up an O2 sensor for my Tahoe too, and it runs about $110...

Anyways, I'll get back to you all with the results in a couple of weeks when I return.


Ken

 

First of all check the wiring and connector related to the TPS. Make sure things are clean and maybe use a bit of that connectivity grease.

Second, turn the key to the ON position and check the voltage from the TPS. It should be about 0.54V at closed throotle and move upward smoothly as you open the throotle plates and reach between about 4.5V and 5.0V.

Maybe you simply need to adjust it. Save you some bucks. But if the voltage does not increase slowly while you are opening the throole plates, then you need a new TPS.

Good luck.

 

I just changed the TPS sensor in my neighbors TPI Vette and it did the EXACT same thing. Almost 5v at idle, with a wandering idle and the same code. I put on a used TPS I had and problem solved. He then went out and bought a new one, problem still solved. Good luck -Jim

 

Just an update.
Got back from a 2-3 week roadtrip/vacation yesterday and picked up a new TPS on my way home. Slipped that puppy in there today and it works like a charm!

Thanks for the help guys!


Ken