91 Chev truck TPS

[Eric Wettschreck]

Hi Guys.

91 chev 1/2 ton, 4 x 4, ext cab, 5.7, auto trans.

The other day while coming home from work everything was fine. While cruising at 60 mph all is good. As soon as I tapped the brake to turn off the cruise the service engine light came on. I stopped at a stop sign, hit the foot feed, and the light came off. Drive aboot 10 miles, another stop sign, same thing happens. When I hit the foot feed, the light comes off.

Same thing happened this morning while coming into work. This time however, when I pulled into the shop it was idiling fast, like 1500 rpm or so.

I hooked up our auto x-ray code reader and got the following code....."22, throttle position indicator too low."

My question(s) are..Is this telling me the TPS is bad and needs to be replaced, or, is there an adjustment on it I need to make? I don't understand why it says...."Too low."

Thanks fellas, Merry Christmas.

[Macgyver55]

Sounds like the sensor is the problem Eric. "Too low" is the voltage reading it is getting at the computer. Do you still have one from the old truck?

Forget the other one, I looked it up and its a different TPS.

[Whoaru99]

Many/most tps can be adjusted. Generally speaking, on GM of that vintage, tps should be about 0.50 volt at idle. There is some leeway before a code is set but don't recall what that is, +/- 0.05 I'd think should still be in the range though.

To adjust just loosen the two mounting screws just enought to rotate the sensor until you have the right voltage then lock it down.

[Macgyver55]

True, and its not all that uncommon for the older ones to get out of adjustment. If you can get the proper reading on both the idle voltage and the wide open throttle end you should be good to go. I was just thinking if he had the other one to put on there it would be ok to try that too, but it looks like they are different.

[Eric Wettschreck]

So, are yous guys telling me this is more than just "Unbolt the old one and bolt in a new one?" If I replace it I have to adjust it also? .5 volts at idle, anyone know what the WOT voltage should be?

Mac, yes I still have the rusted out 89 chev parked behind teh garage. I've already ripped a few parts off of it thanks to the missis hitting a deer with the 91.

[Macgyver55]

Like who said, try adjusting before replacing. Sometimes it is wear in the throttle plate shaft or the throttle body housing that causes the change in adjustment, so dont be surprised if your reading isnt always consistent.

[Whoaru99]

No, not just a straight bolt-on and go.

Typically around 4.5V at WOT, but generally that just falls where it may after you set the idle voltage properly to ~0.5V. There isn't a WOT adjustment, per se.