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Discussion Starter #1
I’ve got a 2014 Cherokee Trailhawk with the 3.2 v6 and have been fighting a cylinder 4 misfire (p0304). After new plugs, gaskets, injector, and swapping coils the dealer is now telling me that I need a new PCM. Including diagnostic fees it’s going to run me almost $1,200. The PCM is very accessible in our cars, is this something I can buy refurbished and replace myself?
 

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I'd find a new dealer..........its very very unlikely a PCM goes bad and causes misfires. As for PCM's they are dirt cheap (Around $100)


Make sure you get a PCM from the same year and engine cherokee, then take it to the dealer to get programmed, will save you a bunch of money
 

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Discussion Starter #4
Update.

I purchased a used PCM and tried to have a local independent shop near me reprogram it. They’re telling me that they are having an issue reprogramming and are getting an error because the PCM had already programmed. Does this sound correct? Or can the VIN numbers only be reprogrammed at the dealership?

also, were about to reach 100k miles and are out of warrenty
 

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Update.

I purchased a used PCM and tried to have a local independent shop near me reprogram it. They’re telling me that they are having an issue reprogramming and are getting an error because the PCM had already programmed. Does this sound correct? Or can the VIN numbers only be reprogrammed at the dealership?

also, were about to reach 100k miles and are out of warrenty
Independent shop isnt going to be able to do anything. In theory IF you had HP Tuners MPVI2 & AlfaOBD you could clone the PCM and write the VIN to the new PCM. Your best bet is to do it at a dealership. Is the vehicle still driveable are you absolutely sure its the PCM?
 

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Discussion Starter #6
The vehicle still drives with the original PCM. I just have an having a misfire issue (p0304). I’m not convinced that the PCM is the issue however the dealer tells me that their testing points to the PCM being bad and there’s nothing else they can do until the PCM is replaced. But when I asked for an explanation and what tests they ran I was told they don’t share the techs notes with customers....

Also, this misfire is accompanied by the lights dimming, Interior and exterior and only seems to happen at low idle. When driving or when the car is cold and idle is a little higher there doesn’t seem to be an issue. I asked them to check the battery and alternator and was told they are both fine.
 

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@Ranch’14
Seeing you have the 3.2 and I went though a similar misfire issue. Mine turned out to be failing roller rocker bearings which scored and damaged 2 camshafts which caused 2 separate misfires about 10k miles apart. First failure was the right side bank and then the left side soon followed. First time was a ticking noise along with a cel. Second failure there was no ticking but a misfire cel. Yours might be similar if you have done plugs, injectors etc. I would mention the pretty common 3.2/3.6 roller rocker bearing failure to your dealer. They should atleast check the above before saying its a PCM. You can google pentastar ticking or roller failure to learn more.
 

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<snip>
Also, this misfire is accompanied by the lights dimming, Interior and exterior and only seems to happen at low idle. When driving or when the car is cold and idle is a little higher there doesn’t seem to be an issue. I asked them to check the battery and alternator and was told they are both fine.
The lights dimming on a rough idle is normal, the alternator can't output properly below normal idle.

If you've done plugs and coil packs, I'd also think roller rocker bearing... as @jcool001985 mentionned...
 

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This is why i suggest something like HP Tuners not just for tuning, because of the scanning for codes and in depth engine monitoring. If you had a log like this you could pinpoint which cylinder is misfiring along with a bunch of other PID's to determine exactly what the problem is.



Misfire logs as well by cylinder, also its quite normal to see a misfire here and there, its when multiple ones happen that trips the CEL or when it flashes that it becomes an issue
 

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The vehicle still drives with the original PCM. I just have an having a misfire issue (p0304). I’m not convinced that the PCM is the issue however the dealer tells me that their testing points to the PCM being bad and there’s nothing else they can do until the PCM is replaced. But when I asked for an explanation and what tests they ran I was told they don’t share the techs notes with customers....

Also, this misfire is accompanied by the lights dimming, Interior and exterior and only seems to happen at low idle. When driving or when the car is cold and idle is a little higher there doesn’t seem to be an issue. I asked them to check the battery and alternator and was told they are both fine.
Hi Ranch'14,
Thank you for sharing your concerns here. Feel free to send our team a private message with your VIN so that we may look into this further for you.

Kathryn
JeepCares
 
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