P0121 TPS code FIXED, new Intense PCM installed - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat

1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-12-2005, 10:30 PM   #1
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Default P0121 TPS code FIXED, new Intense PCM installed

Hi guys, I found out the source of the P0121 TPS range/performance code that cropped up after I had reinstalled everything from my upper/lower intake gasket install last week. Even though the Series II 3800 does not have an adjustable TPS, the holes in the TPS itself (which have metal bushings in them) are still slightly larger than the screws. You can wiggle the TPS on the screws enough to make a few tenths of a volt difference. Apparently my TPS, as installed from the factory, caused an idle voltage that was borderline too low, but not low enough to set an out of range code. When I reinstalled the TPS any which way, it set the idle voltage just enough lower that it went out of range. I measured the idle voltage as 0.30 volts, and the max WOT voltage as 4.17. I drilled the holes out to 1/4" and used washers on the screws, and obtained 0.55 volts at idle and 4.32 at WOT. I installed the Intense standard PCM as well, which brings my shift points at WOT up to a true 6000 rpms, I have no top speed limiter now ( the car should do around 145, with the KYB super firm struts and the largest available sway bars, the car will defiinitely handle at that speed), and the timing is bumped up a lot (I have to run 93 octane now). Hearing the underhood symphony of the Series II n/a motor at 6000 rpms is really a thing of beauty.
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Old 01-13-2005, 07:08 AM   #2
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glad to hear the problem is sovled
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Old 01-13-2005, 04:42 PM   #3
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you should be happy with the TPS adjustment alot have done it here and have good results and the PCM should make it all the better
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