Hey folks,I was out awhile ago warming up my 1984 coupe,the coolant temp after about inutes was reading at 163,it was Idleing at 800 rpm,I just bumped the gas pedal with my foot and the CHECK ENGINE light came on so I checked it with my code scanner and it through out the code 21 and my code book says that means"TPSsignal voltage is high durin idle or deceleration."
The light stays on now.
Can anyone tell me how to fix this poblem? Replace sensor?adjust something?
I finally found my big manual and I can't find anything about the voltage readings at the TPS or what to do for it.
Any help is appreciated,Thanks daddue11.

You can adjust your TPS, its typically on the passenger side of your throttle body is on a hinge so to speak, loosen up with a torx star wrench..... shift forward and backwards to adjust, I have a scanner, so I can see the voltage, but if you do not have one, you can put a multi-meter on it to see the voltage at idle and then wot.

But, not sure this applies to you, I have an 85 with a TPI based motor, you have a crossfire motor.

good luck !

Thank you very much for your reply sir,another person told me just about the very same thing and told me that it does that on the crossfires sometimes when you goose them when they are Idleing and the throttlebody doesn't close back all the way.
I'll check this all out in the morning.
Once again,Thank you sir. daddue11

Stolen from others:

The std method for setting the TPS voltages is to first set base idle to 450rpm and then adjust the TPS for .54Vdc and 4.6-4.7Vdc.

However, you can get a pretty good low voltage setting with normal throttle setting by adjusting the TPS low value to around .7Vdc. The higher the better until the ECM throws a code 21; then back off till you no longer get the code.
Then adjust the TPS for the max value at WOT.

If your scanner is seeing only 1.5Vdc at WOT when your DMM shows >4Vdc there is something wrong.

Anyway, first get the highest low and high TPS voltage settings on the DMM possible without throwing the code 21.
Then work on why the scanner is not showing the correct voltages.

If he is going to set the TPS low value to .54Vdc he must first disable the IAC module and use the set screw to achieve an idle speed of close to 450rpm. When using this method I prefer to set the idle voltage to .65Vdc, which will not throw a code 21.

The goal here is to get the two voltage values as high as possible to enhance throttle response and yet not throw a TPS code.

If you want to do both of these settings "by the book" the methods of adjusting the base idle and the TPS voltages are detailed on my site.

You can only adjust it to the minimum value, after that you have to rely on the TPS is good and the throttle linkage is not hung up some where or the carpet is blocking full pedal travel. Disconnect the throttle cable at TB and manually open the throttle and see what you get for the high side.

Turn the car on and check the voltage between the top 2 pins. It should be about .55-.65V.

You can stab the wires with your voltmeter prongs, or stick some paper clips into the connector to contact the wire.

If it isn't .55-.65, loosen the two torx screws and rotate it until it is.


(I'm 90% sure it's the top two wires, but if that reads 4 or 5 volts, it's the bottom two.)

Thank you all very much for this valuable info. I just got home since I've posted last(took my mother to the hospital with pnuemonia). I'll post on the results of my attemped to adjust th sensor voltage when I get a few free moments to do it.
Once again I'd like to thank all for the help and the quick replies. daddue11