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Old 01-16-2007, 03:30 PM   #1
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Default P0121 - Throttle Position Sensor

I'm getting this code. I have replaced the TPS and spliced on a new connector, and I still get the code. Anyone have any ideas? I was thinking that maybe since the TPS wire runs right next to the alt that maybe it's getting some kind of weird induced current and screwing with the PCM? Is that possible? I also read something about the WOT screw being set wrong and maxing out the TPS voltage? What's that all about?

When I'm doing logging the TPS never stops reading.
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Old 01-16-2007, 06:59 PM   #2
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I have replaced several of these myself here lately, but mine have been broken..
the spring inside the TPS wasnt letting the sensor spring back to 0, so the pcm was setting off a code..
dont know whats wrong with it this time.....
Post up if you find something out...
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Old 01-16-2007, 07:18 PM   #3
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I think I figured it out, I think it's in the tune. There is a table for TPS vs RPM Test Lower table in the engine diagnostics section of the tune. This table basically says that for a given RPM, TPS is expected to be above a certain level. I'm idling at 750 RPM, and the 800 RPM cell was filled with 1% - saying that when the engine is at 800 RPM, the PCM is expecting the TPS to be at least 1%. So for my 750 RPM idle speed, the PCM is expecting to see probably somewhere around .8 or .9% throttle position. I think this is where the problem is. I went ahead and put my 800 RPM cell to zero. Gonna do some more tuning tonight, we'll see if that fixed the problem.

Apparently this is a fairly common problem for people running bigger cams with higher idle speeds.

http://forum.efilive.com/showthread....ighlight=c3907
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Old 02-15-2008, 12:49 AM   #4
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Quote:
Originally Posted by thunder550 View Post
I think I figured it out, I think it's in the tune. There is a table for TPS vs RPM Test Lower table in the engine diagnostics section of the tune. This table basically says that for a given RPM, TPS is expected to be above a certain level. I'm idling at 750 RPM, and the 800 RPM cell was filled with 1% - saying that when the engine is at 800 RPM, the PCM is expecting the TPS to be at least 1%. So for my 750 RPM idle speed, the PCM is expecting to see probably somewhere around .8 or .9% throttle position. I think this is where the problem is. I went ahead and put my 800 RPM cell to zero. Gonna do some more tuning tonight, we'll see if that fixed the problem.

Apparently this is a fairly common problem for people running bigger cams with higher idle speeds.

http://forum.efilive.com/showthread....ighlight=c3907
sorry to bump this but I've got the same issue going on except I've already replaced the TPS sensor twice and it's throwing a code and misreading at idle sometimes and also while driving. Sometimes I will step on it and it will up shift. Other times I will barely touch the gas and it won't shift until 3k rpms. I'll try checking this out in the tune though and see if it helps at all
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Old 02-15-2008, 12:49 AM
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07, 2001, 2007, chevy, code, gto, p0121, pcm, po121, rpm, silverado, table, tps, truck, voltages


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