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OT: GM tech's, need procedure to adjust TPS on 3.8

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Old 04-08-2003, 04:18 PM
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Default OT: GM tech's, need procedure to adjust TPS on 3.8

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!
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Old 04-08-2003, 04:33 PM
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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.
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Old 04-08-2003, 04:38 PM
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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.
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Old 04-08-2003, 05:17 PM
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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?
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Old 04-08-2003, 07:18 PM
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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
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Old 04-09-2003, 08:07 AM
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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.
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Old 04-09-2003, 09:51 AM
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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.
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Old 04-09-2003, 11:45 AM
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Default Replace the TPS

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

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