I'm getting a "21" code, which indicates a high voltage reading for the TPS. Car is a 1988 Olds Cutlass Ciera, 3.8L multiport EFI. (yeah, it's my "pimp-hooptie")

What is the proper procedure to adjust the TPS? I have hunted around a little on the web, but could not find anything that directly addresses this. My best guess is to put a DVM on the lead going back to the ECM (Blue wire?), and check for about .5 volts when throttle is closed. Is this correct?

Thanks for any input!

I think the TPS voltages varry from car to car...i know that my Jeep Grand Cherokee was supposed to be set as close to but not at .7volts....
Would you be able to just call the dealer and ask the parts guys if they could look it up for ya....I'm sure it would be like pulling teeth but ya never know..ya may get a nice tech there.

Its been a while and I'm sure Ill be corrected if I'm wrong but I believe that idle should be [email protected]. generally I've not seen them come out of adjustment, Its prolly bad.

There should be no "adjustment". Closed throttle should be about .5 volts. WOT should be no higher than 5.0 volts. Very rarely do I see them over 4.6, 4.7. More than likely a bad sensor. Is the gound and power good with the key on?

most of the early 3.8's had screws that locked the TPS in place, you could loosen then move the TPS till you get your idle setting, about .5 volts on the signal wire[output of sensor], on this 3 wire system, you have a 5 volt reference, full throttle should be around 4.6 to 4.7 volts,
good luck

make sure the ground side of the sensor is properly grounded. A poor ground path will drive the voltage up on the sensor return line. Probably a bad sensor but hey "Test twice,fix once" . If it needs replacement, the GM rule of thunb is 10% of reference voltage at idle.

I checked it last night. First I checked the gray hot wire, and it had 5 volts. Unfortunately I grounded it to the battery instead of checking the ground at the plug. Probably need to check that to be sure.

I did test the reference lead with the key turned on. It initially read something like .24 volts, which is lower than it should be. At WOT I think it went to 4.6 or 4.7, but it seemed to drop out to .4 or so in a few places as the throttle was opened. That indicates a bad TPS to me, but I would expect it to manifest a symptom while driving the car, like a dead spot or stumble at part throttle, and I am not getting that.

Thanks for all the help. I'm going to double-check the ground lead, then take the thing off and clean it up to see if that makes a difference.

These parts are not fixable. There is no adjustment on it.

Wannabe in Motor City

I made this account 20+ years later solely to correct your guys’ BS!
The ‘red dot’ 3.8L v.6, very distinct from and used PRIOR TO the LN3 3800, found as an option in the 1988 Oldsmobile Cutlass Ciera Cruiser, 100,000% has an adjustable Throttle Position Sensor. The sensor has two big channels for you to rotate the sensor around the mounting screws. From what I have read, closed throttle should measure 0.45 volts from the middle circuit that returns to the ECM.

If you listen to the two members I quoted and install your new TPS sensor on your 1988 red dot 3.8 without calibrating it (as I did) your car is going to have a near constant check engine light until you adjust it.

h


Here you go, in the flesh diagram. A 1988 and older 3.8l red dot V6 found in the 1988 Oldsmobile Cutlass Ciera Cruiser does have an adjustable TPS sensor. The goal is 0.40, volts plus or minus 0.05 volts.

THIS DOES NOT APPLY TO 1988 LN3 3800 motor. THOSE ARE DIFFERENT and do not look adjustable but I can’t confirm 100,000%