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Discussion Starter #1
Hello,

A couple years ago I had the engine rebuilt in my 2004 Turbo PT Cruiser. About a year after that I started getting an error code p0508 when the engine light would came on and the car would die. Mida's changed the camshaft sensor but that didn't fix the problem. They changed a wire that went from the computer to the engine (i think that's where the wire goes) and that seemed to have fixed the issue. Then about 2 months ago the engine light started coming on again and the oil light would come on and then the car would die. The error code is the same P0508. I took the car to the dealership and after testing it for a week, trying to get the engine light to come on, they figured out that I need a new engine wiring harness and a new Engine Control Module which total costs equal $3k+! I can't afford to put $3000 into that car. I took it to carmax, they offer to give me $2000 for it. I would like to save the car since it runs really good.

I'm wondering if changing the Engine Wiring Harness is something I could do myself if I had a book? Has anyone had to replace theirs before? What advice would you give to me? Do you think it's better to salvage the car to Carmax for $2000 or what????

Thanks!
 

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Welcome to the forum first off. If it were me, I would investigate the wiring harness more rather than take it or sell it. The engine control harness itself is not that big compared to some of them out there, and all the wiring ends only fit one way, all the connectors are specific and can't be swapped accidently, or they are marked as far as the injectors go.

Now, the P0508 is the IAC, intake air control switch, located on the back side of the throttle body. Try pulling it off, cleaning the connections and reinstalling. There is a red tab that has to be released or pried up before it comes off. Check the wiring from it to the PCM or as far as you can follow it, look for breaks, cracks, oily conditions that may make it short. the idea is to determine if it is an IAC problem causing the shutdown or the IAC is faulty. What with the location of the wiring and stuff to it, it may have become damaged during the rebuild way back when, so a whole wiring harness should not be necessary.

Keep us informed of what you find, wiring problems tend to be intermittent, bad harnesses and PCMs tend to be constant, especially when a certain set of parameters are met, such as before the car is warmed, or when the car is warmed up, or let's say the harness is flexed in a corner, hard acceleration, a certain speed, something like that.
 

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Discussion Starter #3
About a month ago a mechanic changed the IAC sensor. Is this the same thing you're talking about now?
 

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Replacing things is generally what a mechanic will do when they can't find the problem. Replacing the wiring harness and PCM will probably cover all the bases, but isn't what I would do if 99.8% of the harness is OK. You need someone who will Diagnose this.

P0508-IAC VALVE SENSE CIRCUIT LOW
When Monitored: Engine running. Battery voltage greater than 10 volts.
Set Condition: The IAC sense circuit is less than 175 mA. One Trip Fault.
POSSIBLE CAUSES
IAC MOTOR OPERATION
IAC MOTOR
IAC MOTOR CONTROL CIRCUIT SHORTED TO GROUND
IAC RETURN CIRCUIT OPEN
IAC RETURN CIRCUIT SHORTED TO GROUND
IAC MOTOR CONTROL CIRCUIT OPEN
PCM
 

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Exactly what I am talking about. Given the IAC has been changed, check the wiring from it, ImperialCrown lists the checks to do, double check those specific wires to the computer (PCM). We just may save you several thousand dollars.
 

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Discussion Starter #6
I will take this by the mechanic and see if he can check it out.... Thank you. I really hope this helps.
 

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Discussion Starter #7
I took this to the mechanic. He said he will go through these steps but he did say that since Midas spliced the wires last year and the error is coming on then maybe none of this will work. I'm not a mechanic so I don't know. Any ideas if the wire thing could affect the results of this test?
 

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So now you are talking spliced wires, which may be the problem to begin with. Need to look into this a little more than what you are being told. If nothing else, the wires that were spliced should be redone properly, as in soldering the wires to ensure a proper connection. It may be what the problem is. Save a whole lot of money by replacing only the wire(s) that have been spiced with proper connector ends in the proper connections on both ends, alleviating a splice of any kind. Dealer or even possibly NAPA carries the proper connectors, have it done right and save a ton of money. Take it actually, to an auto electrical shop. I have one here in San Diego that can wire anything properly, it's what they specialize in, should be something near you wherever you are.
 

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Discussion Starter #9
Hi Dana or ImperialCrown, my mechanic said he will gladly troubleshoot this to find the issue but he has some questions and would like to chat or talk. Can you please give me a phone number to call or text? Or let me know what's a good way to communicate. I told him he can post here but he doesn't have the time to post and wait for a reply so he asked if he could talk to one of you.... you can send me a private message to [email protected] Thank you very much!

btw I'm in Houston, TX
 

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Discussion Starter #10
Is there anyone my mechanic can talk to about fixing this? He has questions about something and I really need my car fixed. Please let me know if you are willng to help. Thanks~
 

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It's pretty simple recommendation: You noted you had some wires setting off the error code for the AIC that were repaired. Replace the wire with the proper connections between the AIC to the computer connection, this break may not be making proper connection. If you can find another PT Cruiser in the salvage yard you should be able to disconnect the wire on both ends and simply swap it out.
 

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Well, I'd give you my phone# if I thought I could explain it, but if this guy is truly a decent mechanic, he should be able to understand what's being said. Heck, I've had two brain surgeries and suffer from chronic CRS, but I can figure out what Dana and IC are both saying. Find the wires that Midas spliced, remove them and put some new wires in PROPERLY.
 

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It is a simple 2-wire circuit. If the wires and connections are OK, then it is either has to be the IAC or PCM at fault.
I sent my e-mail address in a PM to the poster if he needs it.
 

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Discussion Starter #14
I had to remove my car from the shop because the owners were starting to complain about it being there too long. The mechanic is new and I'm not sure how experienced he is. However, he did replace the wire that midas "fixed" and the freaking car stopped working the same day! I had just picked up my baby from daycare and the oil light came on and the car died. It wouldn't start back up. I popped the hood and wiggle both ends (the connectors) of the wire he replaced and the car started right up. So, I'm assuming the connectors are bad. You said NAPA should have the connectors I need? I will take my car there and try to get the connectors and then look for an electrical shop to replace them. Thanks for your help. I really appreciate it. I can't afford to keep paying mechanics to diagonose my car and charge $85 an hour for labor. It's getting rediculous!
 

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ImperialCrown... thanks for the email address. I was going to reply by email but figured to keep it public in case anyone else has this issue, they can benefit from it. First, can I post pictures on here? I want to take a picture of the wire that has been spliced so you can see which one it is. The mechanic said the wire colors don't match. The wire comming from the IAC plug is BROWN, the wire coming from the computer harness is PURPLE/BROWN. Midas has those two wires connected with a black wire. Then there is a cut wire tied in a wire bundle that is PURPLE/BROWN which the cut end is not connect to anything. My mechanic replaced the wire that Midas did but it didn't fix the issue. Like I mentioned in the post above, there seems to be a short in the IAC plug or the computer harness.
 
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