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Uniblurb 06-25-2013 01:48 PM

Code 24, TPS help
I have a 93 4.0 XJ w/240K miles and when the AC is on it doesn't seem to want to idle high enough while dropping down some. In fact I can hear a relay behind the bottom part of the dash to the left side of the steering column clicking on/off. Will say it's hot out, 91 w/real high humidity, and this old 4.0 motor tends to labor w/AC on.

Did the key trick and found fault codes 24, maybe 25 once, as can be seen below.

24. Throttle position sensor input above or below acceptable voltage. TPS signal does not correlate to MAP sensor.
25. A shorted or open condition detected in one or more of the idle air control motor circuits. Actual idle speed does not equal target idle speed.

This is the original TPS and about a month ago I cleaned the throttle body and the IAC w/o moving/twisting the pintel. For the past couple years I've had problems with the idle going up/down particularly in the winter. When real cold out it will almost stall when first starting, spit & sputter, and then the idle will pick up real high. Thought this could be the crank sensor, bought a new OE/Mopar one, but never installed it.

Haven't checked the voltage going to the TPS yet and do you just do this with the key on/probe the plug itself when disconnected, or have to back pin the connector with it running? And if the voltage is wrong, believe spec is just under 5V, what do you check next? Maybe I need a new TPS after 20 years and 240K miles? I also don't understand why the relay is clicking on/off behind the dash?

Thanks for any help!

AVR2 06-26-2013 03:16 AM

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I've got the 1993 4.0L powertrain diagnostic manual. When I get home tonight I'll check out the factory procedures for investigating codes 24 and 25.

Uniblurb 06-26-2013 10:10 AM

Thanks for checking AVR2, appreciate it!

AVR2 06-26-2013 12:01 PM

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It's being a PITA to scan because the manual doesn't fold flat. Bear with me, I might have to finish this tomorrow :cool:

Here are the first few pages...

Uniblurb 06-26-2013 05:45 PM

Thanks for the info and those diagrams help a lot! Nice to know the color of the wires along with which cavities in the PCM connector the TPS is connected to.

I'm just a little confused on the last diagram on the left where there's a jumper wire between between 1 & 2 in the plug. Once this jumper wire's in place should you be able to read 4-5V in cavity 3 in the plug with the key on? Would assume you have to put the red probe of a multimeter in cavity 3 and then the other probe to any ground.

If these storms ever stop around here I'll do some testing. Thanks again!

AVR2 06-27-2013 04:35 AM

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Originally Posted by Uniblurb (Post 15611329)
Once this jumper wire's in place should you be able to read 4-5V in cavity 3 in the plug with the key on?

The facing page (which I will aim to scan tonight, and I'll try and get a better scan of that diagram page) will have the flowchart with the details.


Would assume you have to put the red probe of a multimeter in cavity 3 and then the other probe to any ground
If you don't have a DRB, then yes. If you do, you can plug a standard positive multimeter probe into it and then put it into multimeter mode. When you do that, the DRB provides its own ground through the OBD or CCD connector.

Uniblurb 07-01-2013 07:15 PM

Well I finally got around to doing some testing on my 93 4.0 XJ between rains.

Used the follow info on the TPS connector sockets/cavities from the previous diagram.

1 BK/LB - Sensor ground
2 OR/DB - TP sensor signal
3 VT/WT - 5-volt supply

Back probed the #2 TPS signal wire with the key on and connected my multimeter set to DC between #2 and a fender ground screw by the PCM. With the throttle plate closed position it read .98V and the voltage moved up smoothly until the plate was fully opened at WOT which read 3.84V.

Then to double check the #1 sensor ground I also back probed this ground wire with the probes/clips on numbers 1 & 2 while the voltage read exactly the same as above; .98V at the idle position and 3.84V at WOT. According to the manual I was going by this is real close to spec which is supposed to be 1V and 4V.

I also checked the #1 ground wire resistance between the screw on the fender by the PCM, along with the neg on the battery, and they both read infinity.

Then with the connector removed I installed a jumper wire between #1 ground and #2 signal wire and the reading at #3 power supply wire was 4.96V. This is almost exactly the 5V spec.

So as far as I can tell the TPS is working correctly and the wiring going to it is good. One odd thing I noticed before even turning the key on is the #2 signal wire read .06v with the throttle plate closed and .24 at WOT. So evidently a little voltage bleeds through the PCM to the TPS even with the key/power off.

I'd appreciate it if someone could verify that the TPS is working correctly from the above info or do I need to do some other types of tests? Thanks!

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