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Old 01-13-2017, 01:25 AM
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Stalled, Crank but no start, missing 5 volt signal

Our 2000 Wrangler Sport 4.0L, stalled on the washboard in the desert. It was as if the engine just cut out. I now get a yellow engine light, NobuS on the odometer, no gages and it cranks but will not start.
I have found that I do not have the 5 volt signal going to the CPS or the speed sensor. I pulled the gages and cleaned the contacts. All the wires look good to the O2 sensors, and other components, except the CPS harness which I replaced and verified are good to the ECM, and did an Ohm test on the CPS. Not sure where else to go? The loss of the 5 volt signal concerns me. Please help.


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Old 01-13-2017, 09:19 AM   #2
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Since you have already cleaned the dash cluster, I would start next with disconnecting the battery, then cleaning and tightening the terminals along with checking grounds under the hood.
See if that will reset the code and if it will start.

My initial suspicion is a faulty PCM so you will need to check for 12V feeding into the PCM and 5V coming out. Also check for faulty connector wiring at the PCM.

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Old 01-13-2017, 10:36 AM   #3
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Check the wiring harness for any damage. It runs along the firewall so the likelihood of it chaffing on something is pretty high, especially on washboards.
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Old 01-14-2017, 09:30 AM   #4
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Check the wiring harness for any damage. It runs along the firewall so the likelihood of it chaffing on something is pretty high, especially on washboards.
I had that very problem. A wire that powers the PCM shorted out on the A/C accumulator and blew the associated fuse. Checking fuses might be worthwhile.
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Old 01-14-2017, 02:13 PM
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Need a new PCM

Thank you all for your suggestions. I picked up an OBDII code reader tool today and of course due to the fact that I do not have the 5VDC the tool keeps reading error. I have traced back all my wiring and everything is good I had to recover some of the harness with spline and good cloth electrical tape. I am leaning hard on it being the PCM just due to everything else seeming to check out. I cracked the case and it does have a faint smell like burnt electronics. I am a server engineer for Hewlett Packard so I know that smell very well.

So does anyone have a recommendation besides AutoStone or O'Really auto to purchase one?

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Old 01-14-2017, 05:44 PM   #6
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So does anyone have a recommendation besides AutoStone or O'Really auto to purchase one?
There are plenty businesses who specialize in ECM repair and/or exchange.
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Old 01-15-2017, 08:57 AM   #7
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First see if 5 volts at proper pin on ECM

If not try an external 5 volt source like a Walmart USB automobile hub or a cell phone charger

If that makes it run then you know the PCM 5 volt supply is bad


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Old 01-15-2017, 10:04 PM   #8
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If any sensor that is connected that 5v source shorts out, then it will kill all the sensors. Connect a voltmeter to the 5v source wire then disconnect each sensor until power returns. Had a durango quit running and ended up being an internal transmission sensor shorted.

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