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New symptom for this strange engine problem\code.

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Old 03-11-2013, 12:51 PM
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Year: 1992
Model: Cherokee
Engine: 4.0l I6
Default New symptom for this strange engine problem\code.

It's a 92 jeep cherokee laredo with the 4.0 i6.

Started throwing a code a while back "TPS over 4.92v". Replaced the TPS and a bunch of other stuff to no avail. The only effect of the code seems to be that the jeep shifts wrong. Like, it shifts at 2k EVERY time no matter if you're being gentle or flooring it.

What I've recently found is that the code (and bad shifting) don't appear until after it's warmed up for the first startup of the day. First drive of the day there is no code and it drives fine, then after it warms up the code pops on and the bad shifting starts. Letting it sit for a few hours and get cold again doesn't make the code go away, unless it actually sits all the way over night.

I'm thinking maybe a bad transmission control module, but A) what does that have to do with the TPS? And B) the parts store guy swore up and down that my year\model doesn't have a tranny control module, but I swear I saw one last time I was underneath looking around.

Thanks for any help!
Old 03-11-2013, 07:21 PM
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Anyone?
Old 03-11-2013, 11:41 PM
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What is the supply voltage to the TPS?
Have you measured the actual signal output? (center pin)
How about the ground, does it show almost no resistance to battery (-)?
Yes you have a TCU, parts store guy is wrong. I don't think it's your problem though.

The TPS is nothing but a rheostat with 5V applied to one end and ground to the other. The wiper arm moves between the two when the throttle moves. The output voltage should be a couple hundred millivolts at idle and just under 5V with the throttle wide-open.
If the ground is bad it'll output 5V no matter where it's positioned, the TCU will think you have it floored all the time and shift very late. I'd check that first, the ground connection, preferably while it's acting up.

Last edited by Radi; 03-11-2013 at 11:43 PM.
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