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possible TPS failure

1177 Views 8 Replies 2 Participants Last post by  astro355
Ok, A friend told me that perhaps the TPS is or has failed, causing the van to think that the pedal is floored.

By Quote:

"I had a similar issue awhile back with an old Buick. Complaint was long drawn out shifting and trans suddenly dropping out of overdrive and into 3rd at highway speeds and banging into gear. It turned out to be a TPS that was faulty and suddenly maxing out at 4.9v"

And he said every time the TPS spiked, the trans would downshift because the computer thought the driver was flooring the accelerator. It was also causing the trans to delay shifting.

My question is whats the best way to check to see if it is the TPS is faulty, maybe this will clear ALOT up.


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If you have a scan tool, you can monitor the TPS output voltage.

If you don't have a scan tool, get a multimeter and back probe the signal wire. You can monitor the voltage that way also. I don't know which wire it is off the top of my head.
50 volts? It shouldn't be that high. Did you use back probes and measure in parallel for the voltage? Or did you wire the multimeter in series?
No, there is no adjustment to the TPS. So it measured 500 millivolts regardless of the position of the throttle blade?
If the TPS voltage never changes from 500 milliVolts regardless if its at idle or wide open throttle, then that is your problem (or a problem). That voltage is supposed to change depending on the position of the throttle blade.
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