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One of the motors is having misfires in two cylinders, afaik compression, spark plugs and injectors were checked, and they were fine. PCM is suspected to have gone bad. Codes thrown: p0301, p0304.

We would like to connect Jeep's PCM to the Challenger's motor and see if the misfires are gone.

Is that safe?

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There are a couple of things which I believe would make it so I wouldn't do that:

  1. More than likely, even though they are the same base engine (6.1L Hemi), they are still tuned differently. The variance in the tunes could introduce unforeseen problems.
  2. If it is a bad PCM, how do you know if whatever caused it to happen might not do that to the swapped in PCM? It really doesn't make sense to have two vehicles down with the same problem.

Then there's the rub: Will it even fit? I'm not sure on the Chrysler products, but am wondering if the wiring harness will have mating one with the other, which means you wouldn't even be able to get it into the vehicle in the first place to try.

If it's something which you really feel you need to test, buy a used one from eBay or Craigslist. I wouldn't put a known good one which you still need in danger just to prove a diagnosis.

On a separate note, P0301 and P0304 are misfire codes (obviously). Try moving parts around on the same vehicle (ie: move the coil(s) for cyl #1 to cyl #2) and see if the code follows the cylinder. I would mistrust the diagnosis on the parts before I'd believe it to be the PCM ... mainly because its a lot cheaper to change out the coils and/or plugs than it would be to get a new (or even used) PCM. Just a thought.

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They're not going to be compatible. Look at the code on the PCM, and then look it up on an interchange site; you'll find that Jeep and Dodge 6.1 engines never come up in the same list.

Also, to make the PCM work in another car - even one where the PCM is a direct replacement - it needs to be programmed to the cars VIN and Mileage, and the keys need to be programmed to the PCM. That's not something most people can do at home, and it's not something that the dealer will do cheaply. In short - it's a last resort.

I would take Paulster2's advice, and look closer at the misfire codes. You mentioned that 'afaik compression, spark plugs and injectors were checked' - so you're not sure, therefore you should assume that nothing has been done correctly. Check the obvious first - swap ignition coils around (1 to 2, 4 to 5), and see if the codes change to show P0302 and P0305; if they do, then replace the ignition coils with good ones (don't get the cheapest; try to get OEM if possible).

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Very Possible since they are both the same engines, but impossible to answer with out the part numbers from both units. With that info I could cross reference them to see if they have the same base hardware. IF they do have the same hardware then you CAN downgrade the software and re-flash what you need but its not common knowledge even among Chrysler techs so it is hard to get it done unless you send it to the right guy.

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