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Old 10-27-2013, 05:34 PM   #1
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jeep is still dead. completely lost

So I have posted a couple times regarding me jeep and it all of a sudden issue of not running. I have gotten various codes, but none have been consistently repeated, and now I am poping really strange codes like u0155 (instrument cluster loss of connection) p0355 (cps) which was just replaced by dealer oin all this mess. And a p0508. I can't find anything about that code. Checked it a second time and its deffinetly a p0508. Jeep runs for about 2 minutes the shuts off roughly. Usually tripping the asp relay. But then fires right back up and again runs for 2 mins +/- 30 secs. The engine wire harness is shot at the PCM. Looks like previous owner spilled battery acid all over it and its melting. I am replacing that, but today took it apart separated and isolated all the wires, tried to fire it and same situation. Could this be a bad PCM? The harness is covered in old acid and corrosion, but I only saw one wire with a break in the insulation, and the copper inside still looked good. So harness aside any ideas?

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Old 10-27-2013, 07:22 PM   #2
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Quote:
Originally Posted by steel_wheels View Post
So I have posted a couple times regarding me jeep and it all of a sudden issue of not running. I have gotten various codes, but none have been consistently repeated, and now I am poping really strange codes like u0155 (instrument cluster loss of connection) p0355 (cps) which was just replaced by dealer oin all this mess. And a p0508. I can't find anything about that code. Checked it a second time and its deffinetly a p0508. Jeep runs for about 2 minutes the shuts off roughly. Usually tripping the asp relay. But then fires right back up and again runs for 2 mins +/- 30 secs. The engine wire harness is shot at the PCM. Looks like previous owner spilled battery acid all over it and its melting. I am replacing that, but today took it apart separated and isolated all the wires, tried to fire it and same situation. Could this be a bad PCM? The harness is covered in old acid and corrosion, but I only saw one wire with a break in the insulation, and the copper inside still looked good. So harness aside any ideas?
Gray key or black key?
Sounds like the anti theft

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Old 10-27-2013, 07:25 PM   #3
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P0508 Jeep - Idle Air Control Valve Sense Circuit Low

Possible causes- Faulty Idle Air Control (IAC) motor- Idle Air Control (IAC) motor harness is open or shorted- Idle Air Control (IAC) motor circuit poor electrical connection*Help with thisWhen is the code detected?The PCM senses a short to ground or battery voltage on any of the control circuits for 2.75 seconds while the IAC motor is active.Possible symptoms- Engine Light ON (or Service Engine Soon Warning Light)- Engine hard to start- Rough or erratic idle speedP0508 Jeep DescriptionThe Engine Control Module (ECM) controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold, by operating the electric throttle control actuator. The operating of the throttle valve is varied to allow for optimum control of the engine idling speed. The*ECM*calculates the actual engine speed from signals of crankshaft position sensor (POS) and camshaft position sensor.The*ECM*controls the electric throttle control actuator so that the engine speed coincides with the target value memorized in the*ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the*ECM*is determined by taking into consideration various engine conditions, such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan operation, etc.)
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Old 10-27-2013, 07:46 PM   #4
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Black key. No anti theft. I did find the 508 code with more research. When I first started having issues, the idle air control valve part was making a lot of noise, and jeep wouldn't start. Replaced the part, but there was no change, so I cleaned the old part up, and cleaned the throttle body, put it all back together, still no difference. IAC has always been on my mind, but doesnt seem to be the problem. I guess I could buy the part again and replace it just in case, but its a $130 part. Like I also said, codes keep coming up and going away randomly. Like the jeep is just throwing codes out cause it can. I have gotten several codes, one or two at a time, but they go away and something new pops up, and old code is cleared, or sometimes no code. So frustrating.
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Old 11-17-2013, 08:52 PM   #5
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So I have replaced both engine bay harness, and ecu. Used parts off a same make model and optioned jeep. Got lucky with that. Vehicle runs now, but I have a high idle, and showing o2 sensor code. The idle seems to lag once refer, so say while shifting from 2nd to third at 3500rpms, the motor stays at 3500 rpms till I engage third gear. When I come to a stop the rpms stay at 2k-2500. If I tap the throttle it will sometimes drop back to normal. No vacuum leaks. The harness was in amazing shape when it arrived, only one missing connector for batt temp sensor, and all other plugs in near perfect condition. So what causes high, lazy idle?
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Old 11-24-2013, 01:18 PM   #6
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Try cleaning the throttle cables... lube them too and bad o2 can lead to higher idle... not to hard to swap out that
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Old 11-24-2013, 01:34 PM   #7
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A high idle is usually caused by a vacuum leak or a sticking IAC (Idle Air Control) module. The IAC meters air to the engine so it can idle when your foot is not stepping on the gas pedal. When the IAC is dirty, it can hang up & cause idle problems or occasionally high RPMs when it sticks in the open position letting excessive air into the engine. Cleaning the IAC with an aerosol throttle body cleaner normally restores it back to good operation. You also need to clean the oriface in the throttle body the IAC's plunger fits into, a baby bottle nipple brush with throttle body cleaner works well there.

A bad 02 sensor can cause a poor idle, a stumbling idle, misfiring, poor acceleration, poor mpg, etc. but it won't normally cause high engine rpms.
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Old 11-27-2013, 09:58 PM   #8
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I had thought about the iac previously, and did clean it with no change. Last night driving home I popped a 517, and 507. One is battery heat sensor which isn't hooked up (new wiring harness didn't have a plug for it. Will address that later), and second is iac high output. Replaced the part today and reset codes. Drove it for 10 minutes at lunch and no diffrent. Keep looking for vacuum leaks, but not finding any. I am starting to lean to tps.

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