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  #25  
Old 08-21-2013, 07:13 PM
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Re: HELP! Engine/Grounding problems.

Wait for the alternator. A PCM change is going to involve a trip to the dealer unless your WJ is pre skim like our '99 was. Which key do you have? Grey oval or black triangular and what year is your Jeep?
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Old 08-22-2013, 01:58 AM
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Re: HELP! Engine/Grounding problems.

Well I got the oval gray/beige one. Car is from 2000. Slight problem however....if you look at the pictures earlier in this thread you will see how the PCM looks. I was totally coroded and the aluminium was so corroded that the seal had opened up in one of the upper corners....inside was signs ov corrosion in the lover part below the opening.....as John Clease would have said.....the PCM is gone...it has ceast to be....it is no more.
So is it impossible for these guys that are selling me this programed box to enter the SCIM secret code....do they need acces to the keys? How does that work?
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  #27  
Old 08-22-2013, 10:14 AM
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Re: HELP! Engine/Grounding problems.

Frank probably knows a little more about this than me but I believe the pcm has to be flashed to your vin and your key. or it will start for a few seconds and shut off. I would double check with them. They may be selling you a '99 pcm which doesn't have skim and I doubt they're compatible. Who knows they may know something I don't but I don't want to see you get stuck with a pcm you can't use. But if it is a skim pcm worst case scenario is you'll have to get towed to a dealer and they can program it for you. Hope it works out in your favor.
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OK, fine...I'll admit...some amber lamps are good, and necessary.
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  #28  
Old 08-22-2013, 10:45 AM
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Re: HELP! Engine/Grounding problems.

Hello again!

Just ben on the phone with them in the US and asked about the SCIM programing.

What they do is exchange your unit for a recycled unit. I had to give them my VIN number and part number as well as milage. This will be loaded in to the recycled unit and also the SCIM code will be erazed out of the PCM meaning that as long as you have a key fitting the lock no need for any chip data is required. Not 100% but good enough for me...if anyone wants to steal my 13 year old jeep....tough luck!

They promiss a plug and play experience....lets hope this is true...

Thank you ever so much for your concern. This is the cheapest option the way I see it. Getting one from the junkjard and have crysler spend hours on it at 200USD/Hour rate just doesnt add up. Also I have been warned that Chysler will not flash and reprogram 2nd hand PCMs due to liability issues. Ofcorse they want to sell me a new one and thats super expensive I have been warned...better bring the car to the junkjard than picking up a PCM from there....

Ill keep you posted.


Phil
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  #29  
Old 08-22-2013, 11:01 AM
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Re: HELP! Engine/Grounding problems.

What i understood from the manual is that the jeep can run without the VIN and the milage update, it will only set a fault code in the PCM.
However the PCM should know that the SKIM signal is a valid signal, and for that reason each SKIM has its own secret code and this code must be send to the PCM after installation. When the PCM doesn´t see a valid SKIM signal, the engine will start, but shut down after 3 seconds or so.
If the PCM will work without programming the secret SKIM code, then the manual is wrong.
What can be the case is that they just simply deactivate the SKIM code option. In that case you could use just simple keys without transponder.
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  #30  
Old 08-22-2013, 01:05 PM
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Re: HELP! Engine/Grounding problems.

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Originally Posted by Frango100 View Post
Hi Phil, the voltage regulator is part of the PCM. So not sure if this problem is caused by the voltage regulator, or the alternator itself. Clean the connector on the alternator first, to rule out any moisture or corrosion problem. I still have the engine wash in the back of my head and the alternator is partly open and water can easily penetrate in its interior.
A popped diode in an alternator can cause strange behavior.
An alternator specialty shop might be able to make a quick check, or if you have a cheap o-scope that could work.

The alternator uses the diodes to rectify the AC it produces, and they can fail to an open [failing to a short lets out the magic smoke, so you know in an hurry] which leaves too much pulsating on the more or less DC output.

The battery acts as more or less of the capacitor in the circuit.

An alternator ain't cheap, but its cheaper than the entire PCM if you can get someone to check the alternator offline for you.
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  #31  
Old 08-22-2013, 01:26 PM
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Re: HELP! Engine/Grounding problems.

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Well I am back already...I figured Ill take the generator apart and meassure the rectifier. Said and done it all looks normal to me, all diods only letting current through in one direction and all values equal between all diods.

After I put the generator back together and on the car to test run it, the voltage without the B+ cable attached (only field current cable attached) was 13-14 volts. I then attached the B+ cable, again sparks and a drop in idle rpm. I now meassured the current at the b+ terminal as well as directly over the battery terminals and voltage was jumping between 14 and 16.7 volts!!!!

I dont think its the alternator anymore....if it is regulated by the PCM then thats where the problem should be?

I will remove the PCM now but it is located quite wierd.

My question now is if I throw in another PCM will I need to reprogram anything or should it just work assuming its no other issue creating the problem. I will also replace the alternator as I have already ordered it.

Greatful for any tips regarding replacement of the PCM.

Cheers for now!

Phil
Those voltages with the alternator being controlled by the PCM are not good.
Anything over 14.5 to 14.7 volts tends to result in highly reduced battery life [and can void a battery warranty at places where they test your charging ckt before replacing] and anything over 15 can be bad news not only for the battery but for the electronics, and 16.7 is just bad bad news as you could generate enough hydrogen in the battery to make it explode.

I wouldn't be connecting and disconnecting live on a modern vehicle, you could get a voltage spike enough to fry stuff. And never ever disconnect the battery if the alternator is driving any of the electronics. Peak voltages in the 100 range or better can last for a few hundred milliseconds, and a lot of magic smoke can be released.

I don't suppose you have a battery with a warranty from someone like Sears, where you could get a free test?

I tend to agree, sounds like your PCM may be toast, but it could still be something in the cheaper alternator... the PCM will typically just crank up the field current in order to reach the charging voltage of at least 13.8 and then try to keep it under about 14.5 by dropping the field current.

Depending on the response time of your meter, you could have a wierd battery problem, in that the battery acts to damp out the pulsating DC that an alternator and diodes produces. Not as likely as the voltage regulator in the PCM dropping too much current into the field windings [if you have a clamp on current probe, can check that as well] and causing excessive voltage.
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  #32  
Old 08-23-2013, 10:08 AM
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Re: HELP! Engine/Grounding problems.

Hello everyone,

Well i have ordered and waiting for a refurbished and reprogramed PCM. I also bought a "new" generator and will replace them both and see how it goes. The parts should arrive on monday. I will keep you posted.

I took the generator apart and messured all the diods individually. They all only let currant through one way and on my multimeter in diod position the values differed between 585-613.

I "re clamped" all diods and field connections so there should not be any connection issues.

When opening the PCM i found alot of corrosion inside in one of the bottom corners....I tend to believe its the PCM that is toast, but I will be totally lost if both the PCM and alternator swap wont cure the problem.

Keep your fingers crossed!

Thanks a million for all helpful advice and please feel most welcome to brainstorm with me on this.

Regards,

Phil
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  #33  
Old 08-23-2013, 11:16 AM
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Re: HELP! Engine/Grounding problems.

Maybe you could just change the alternator or PCM alone and test, to see which one of the two will solve the problem.
I have never opened the PCM, does it have an open circuit board inside, or did they fill it with some kind of resin?
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  #34  
Old 08-23-2013, 11:51 AM
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Re: HELP! Engine/Grounding problems.

Hi Frank,

The PCM consist of an aluminium "rack or frame" and a thin folded aluminum plate that has been slided on the rack/frame with some glue/seal around and then a few attachment screws.
The tricky part is that the thin circuit boards are attached to the thin aluminum plate and if you try to pull it from the glue/seal attachment around the frame the plate and moderboard wil bend. Dont know how much bending it can handle so I cant see how you can get into the PCM without damaging it.

My PCM was so corroded at one of the plate corners of the aluminium had dissapeared to the point of the seal thus allowing access inside for humidity/water. I might just have managed to get a few drops in there with the engine wash, however the corrosion looked older than 3 weeks so this thing was going to give up sooner or later. I could suggest taking the PCM out, clean it and spray it with some sort of body protection like tectyl or so?

I will change both the PCM and alternator....Imagine I toast the new PCM with a faulty Alternator!

Phil
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  #35  
Old 08-23-2013, 10:19 PM
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Re: HELP! Engine/Grounding problems.

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  #36  
Old 08-24-2013, 01:25 AM
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Re: HELP! Engine/Grounding problems.

Well Frank here you go,

I didnt want to open it up any more as i might have to try and reuse it if I dont get a new one...contactspray or so??

you can see corrosion on the right upper corner due to the cameraflash the picture is not perfect but along the side and the lower part has quite some corrosion too.

se how tightly the circuits are attached to the aluminiumplate.

Phil
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