And lastly, 'cause I didn't want to leave you hanging...

A link to a site that gives you two test methods for your TPS. Read the whole article.
TPS Knowledge is Power

Lash:
Thanks for the info.

No problem! Please let us know what you find.

Hi lash: Since we last talked I removed the TPS, dismantled it (that was fun - they're
not designed to come apart) & cleaned it with contact cleaner and a little shot of WD40.
The replacement part costs $179.95 at the dealer. It'* been fine ever since - no
problems whatsoever.
Thanks for your help. By the way the dealer says I'm full of **** since that part cannot
cause the problem that I was having.

If the TPS is faulty.. it can give false readings to the computer as to what throttle you are requesting.

The problem description made me think the TPS was the most likely cause. I'm glad that you fixed it, but you shouldn't have had to, and it'* a shame that the dealer wasn't competent in that area and gladly took your money and called you names...it'* terrible how ethics in this country have gone to the toilet over the last couple of decades.

Quick question here about this thread:

Why wouldn't this TPS failure have resulted in an error code???
In other words, why did the car think everything was OK when that clearly was not the case?
Is this typical of TPS failures not generating an error code?

Thanks.

i've also got a question about this, hermit, when this was happening how much did you depress the throttle? because if it was idling and you opened up the throttle but it didnt have a signal, the throttle is still physically opening, there would be more air coming in, there shouldve been some effect like maybe the engine would wanna stall out cause its getting alot more air but without a signal the pcm isnt giving it anymore fuel...

Well, your one quick question is really three hard questions and I can't give you definitive answers at this time, but....

In general, error codes are set when certain parameters are all met that meet the requirements to set that code. It sounds like I'm talking in circles doesn't it?

The point being, this doesn't just occur with the TPS, it can occur with many other mechanical/electrical issues. If there is not a sensor sequence or feedback loop that the PCM is set up to recognize, it doesn't set a code. Now that doesn't mean that the PCM doesn't see the issues, they just may not meet the requirements for a code.

That'* one reason we often tell someone to get a full scan or hook up a scanner while driving/running the engine. Then you will see real time data, and if you know what to look for you will often see readings that can help lead you to a problem.

That'* the general explanation. Maybe there'* someone here with more specific knowledge that would like to attempt a more technical and detailed explanation.

This is the description of the TPS and possible codes. The "hard failures" listed in the second paragraph turn on the light. The intermitent failures in the last paragraph set a code but does not trip the light. This is from a 2000, so "your mileage may vary."

The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the PCM calculates the throttle position. As the throttle valve angle is changed as the accelerator pedal moves, the TP sensor signal also changes. At a closed throttle position, the output of the TP sensor is low. As the throttle valve opens the TP sensor voltage increases. At Wide Open Throttle (WOT) , the TP sensor voltage should be more than 4 volts . The PCM calculates the fuel delivery based on the throttle valve angle.

A broken or loose TP sensor may cause intermittent bursts of fuel from an injector and an unstable idle because the PCM thinks the throttle is moving. A hard failure in the TP sensor 5 volt reference or signal circuits should set DTC P0122 or DTC P0123. A hard failure with the TP sensor ground circuit may set DTC P0123 and DTC P0117. Once a DTC is set, the PCM uses an artificial default value based on the engine RPM and the mass air flow for the throttle position, and some vehicle performance returns. A high idle may result when DTC P0122 or DTC P0123 is set.

The PCM can detect intermittent TP sensor faults. DTC P1121 or DTC P1122 sets if an intermittent high or low circuit failure is detected. The PCM can also detect a shifted TP sensor. The PCM monitors the throttle position and compares the actual TP sensor reading to a predicted TP value calculated from the engine speed. If the PCM detects an out of range condition, DTC P0121 sets.