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Old 07-15-2011, 11:37 PM   #1
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Throttle Position Sensor Data

Ok-here is some very interesting data on readings from my TPS. Some time ago, my original TPS went bad and I replaced it with a NAPA version. Today I took some readings on the throttle position percentage on my OBD2 scanner. This is on a 2003 Wrangler Rubicon 4.0L manual.

At idle position, the TPS signal is indicating 12.5% open. At WOT position, my TPS signal is reading 74.5%. Thats right, the closed idle is sending a 12.5% open, and at WOT it is sending a 3/4 open reading!!

I loosened the two mounting screws on the TPS and removed it from the throttle body. At full closed position, it will send a 0% open and at full WOT position it will send a 100% reading! Either this thing is calibrated all haywire or the ECU must have some BIG corrective adaptive memory capacity. I can't believe these readings aren't causing some power and performance loss. The TPS is an important input signal for the ECU and these numbers just don't seem right.

I am going to pick up an OEM Mopar TPS tomorrow and compare some readings. Does anyone have any data or readings from their TPS???? What say you?

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Old 07-19-2011, 06:30 PM   #2
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On the way home tonight, my check engine light came on. Auto Zone was close so I stopped in. The guy said my throttle position sensor was making the light come on. O'reillys was real close and his diagnosis was the same. I don't know anything about that. I do know where the sensor is and that it costs about 35 bucks. Looks simple to change. Will that fix this or do I need to take it in to a mechanic?

Jeff

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Old 07-19-2011, 07:02 PM   #3
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This problem will usually set a TPS voltage out of range code such as PO122, PO120 or PO124. Do you have a number?
Change the TPS if that is the scan code.
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Old 07-19-2011, 09:56 PM   #4
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Autozone printed out a slip for me and it said PO122. I am not sure what you mean by voltage range. Didn't really understand the first post either. Would like to change it myself to save money but I don't want to mess it up worse.

Exactly what does the tps do? What does PO122 mean? Thanks for any help

Jeff
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Old 07-19-2011, 10:19 PM   #5
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PO122 is a low voltage output by your TPS-typical of a failure of the sensor, You should be able to simply replace it with a new one-a simple job but be aware the 2 screws are locktited in and sometimes stubborn to remove. Work them back and forth a little to avoid breaking one off.

The first post is in regards to the output signal levels. The TPS outputs a voltage signal that can range from 0 to 5 volts. The voltage signal tells the ECU how far open the throttle is. A scan gauge gives a % open based on the voltage it is seeing from your TPS. When read on a scan gauge, the readings seemed to be high at idle and very low at full throttle. I have confirmed they are normal range readings for the TPS output. The ECU uses a much smaller range of available voltage than I expected.
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Old 07-19-2011, 10:22 PM   #6
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Your readings sound normal for a non adjustable sensor. Your scanner is just reading a straight voltage and converting it to a percentage based on the standard 0v to 5v, where in reality the Jeep's computer is just reading it as a voltage reading and is supposedly self adjusting.
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Old 07-20-2011, 08:47 AM   #7
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Thanks!! I did some reading on the TPS threads and I think i understand it better so I plan to disconnect the battery to reset codes and change it with an OEM TPS. Hopefully that will take care of it. Thanks for the help.

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