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Discussion Starter #1
Sorry for the long first time post. Spent many hours reading yall's already. 2007 JK with 175,000 miles. I bought it new and for the most part have repaired/replaced whatever problem has come along in those miles. Here is my current unsolvable (to me) issue. I have had a cracked drivers side exhaust manifold (known to me) for a bit but didn't do anything to repair it. Threw a code for a drivers side upstream o2 a few months back, bought new sensor but CEL turned off so never installed new sensor. A couple of weeks ago, new CEL, codes were P0430, P2308 and P0300 and the jeep started running rough, did not want to go much over 40 mph, would shudder around 40 mph and CEL started flashing. Acted identical to a TJ I previously had with a clogged cat and I thought the P0430 code was pointing to a cat. I figured I wasn't going to get anywhere diagnosing with the current exhaust manifolds (unwilling to buy replacements that would crack again) so I ordered new shorty headers, new cats, new o2s, plugs and wires. Installed everything (both manifolds were shot with a couple of bolts already broke off in the heads), cleared the codes and started the Jeep thinking I was ready to go another 175K. Nope, CEL back on but now it only throws the P2308 immediately and sometimes the P0300 after driving it and it runs the same. My next thought was to replace the coil pack but have read a thousand posts of replaced my . . . . but did not fix my issue so I thought I might reach out before I go down that rabbit hole. The Jeep absolutely needed what I have replaced so far. I have the ability to pull live data with my reader but not very good at interpreting the results to chase the P2308 ignition coil 3 secondary circuit- insufficient ionization and the P0300 random misfire. After reading for hours, I am leaning towards my PCM because I can watch all four of my o2s and the upstream's run 0.015 volts, the downstream's not much above 0.00. I have double checked part numbers for correct fit and have cleaned grounds to bat, frame and PCM. Any suggestions are greatly appreciated and I can post pictures of my live data screens if someone needs anything specific. Thanks in advance.
 

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You need to see if that coil has the right inputs to be able to function.

So your coil is part of a waste spark system. This means that your ignition coil actually has 3 coils in it. One coil for 2 opposing cylinders. This means that coil will fire a spark in one cylinder at TDC at compression while it also fires a spark in the opposing cylinder at exhaust. This is the waste spark...doesn't ignite anything.

The ignition coil has 4 wires going to it. It has battery positive from the ASD relay (brown with white stripe wire). Then the ground for the coil is done through the PCM. There are 3 wires here one for each coil. The coil 3 that you are having issues with is the dark blue with orange wire.

Here is how to test this. Get yourself a test light. Not one of the computer safe ones, get one that has the incandescent bulb. I am assuming the power to the coil works otherwise the engine would not start and run. But you can test by hooking the test light clamp to battery negative. Disconnect the ignition coil connector. Touch the pin of the connector (just make contact with the tip of the test light, don't jam it into the connector) for the brown with white stripe wire. Have someone turn the ignition key to on. It should light up for 3 secs or so.

Now to test the ground on ignition coil 3. With the ignition coil harness disconnected. Clamp the test light to battery positive. Touch the pin for dark blue with orange wire. Have someone turn the ignition to crank and crank for 5 secs. The test light should blink really fast.

If the test light blinks, we need to look at coil, plugs, wires. If it doesn't blink, we need to look at wiring, PCM.

Note: you can test the other ignition coils wires in the same way. This way you can compare coil 1 blinking to coil 3.

Note 2: Don't run your engine much with a cylinder (or two which is possible in this case) not igniting. This can pass unburnt fuel to the CATs which can ruin them.

Let us know how the testing goes.
 

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Discussion Starter #6
You need to see if that coil has the right inputs to be able to function.

So your coil is part of a waste spark system. This means that your ignition coil actually has 3 coils in it. One coil for 2 opposing cylinders. This means that coil will fire a spark in one cylinder at TDC at compression while it also fires a spark in the opposing cylinder at exhaust. This is the waste spark...doesn't ignite anything.

The ignition coil has 4 wires going to it. It has battery positive from the ASD relay (brown with white stripe wire). Then the ground for the coil is done through the PCM. There are 3 wires here one for each coil. The coil 3 that you are having issues with is the dark blue with orange wire.

Here is how to test this. Get yourself a test light. Not one of the computer safe ones, get one that has the incandescent bulb. I am assuming the power to the coil works otherwise the engine would not start and run. But you can test by hooking the test light clamp to battery negative. Disconnect the ignition coil connector. Touch the pin of the connector (just make contact with the tip of the test light, don't jam it into the connector) for the brown with white stripe wire. Have someone turn the ignition key to on. It should light up for 3 secs or so.

Now to test the ground on ignition coil 3. With the ignition coil harness disconnected. Clamp the test light to battery positive. Touch the pin for dark blue with orange wire. Have someone turn the ignition to crank and crank for 5 secs. The test light should blink really fast.

If the test light blinks, we need to look at coil, plugs, wires. If it doesn't blink, we need to look at wiring, PCM.

Note: you can test the other ignition coils wires in the same way. This way you can compare coil 1 blinking to coil 3.

Note 2: Don't run your engine much with a cylinder (or two which is possible in this case) not igniting. This can pass unburnt fuel to the CATs which can ruin them.

Let us know how the testing goes.
thank you so much. I’ll do it when I get off work and let you know
 

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Discussion Starter #7
You need to see if that coil has the right inputs to be able to function.

So your coil is part of a waste spark system. This means that your ignition coil actually has 3 coils in it. One coil for 2 opposing cylinders. This means that coil will fire a spark in one cylinder at TDC at compression while it also fires a spark in the opposing cylinder at exhaust. This is the waste spark...doesn't ignite anything.

The ignition coil has 4 wires going to it. It has battery positive from the ASD relay (brown with white stripe wire). Then the ground for the coil is done through the PCM. There are 3 wires here one for each coil. The coil 3 that you are having issues with is the dark blue with orange wire.

Here is how to test this. Get yourself a test light. Not one of the computer safe ones, get one that has the incandescent bulb. I am assuming the power to the coil works otherwise the engine would not start and run. But you can test by hooking the test light clamp to battery negative. Disconnect the ignition coil connector. Touch the pin of the connector (just make contact with the tip of the test light, don't jam it into the connector) for the brown with white stripe wire. Have someone turn the ignition key to on. It should light up for 3 secs or so.

Now to test the ground on ignition coil 3. With the ignition coil harness disconnected. Clamp the test light to battery positive. Touch the pin for dark blue with orange wire. Have someone turn the ignition to crank and crank for 5 secs. The test light should blink really fast.

If the test light blinks, we need to look at coil, plugs, wires. If it doesn't blink, we need to look at wiring, PCM.

Note: you can test the other ignition coils wires in the same way. This way you can compare coil 1 blinking to coil 3.

Note 2: Don't run your engine much with a cylinder (or two which is possible in this case) not igniting. This can pass unburnt fuel to the CATs which can ruin them.

Let us know how the testing goes.
clamped to neg bat terminal: key on pin 2 br/wt lights solid. Clamped to pos bat terminal: pin 4 db/tn and pin 3 db/dg flash when engine is cranked. Pin 1 db/or lights solid with no key on at all. Guessing that means I have a dead short somewhere between coil connector and pcm or pcm is bad?
 

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Discussion Starter #8
You need to see if that coil has the right inputs to be able to function.

So your coil is part of a waste spark system. This means that your ignition coil actually has 3 coils in it. One coil for 2 opposing cylinders. This means that coil will fire a spark in one cylinder at TDC at compression while it also fires a spark in the opposing cylinder at exhaust. This is the waste spark...doesn't ignite anything.

The ignition coil has 4 wires going to it. It has battery positive from the ASD relay (brown with white stripe wire). Then the ground for the coil is done through the PCM. There are 3 wires here one for each coil. The coil 3 that you are having issues with is the dark blue with orange wire.

Here is how to test this. Get yourself a test light. Not one of the computer safe ones, get one that has the incandescent bulb. I am assuming the power to the coil works otherwise the engine would not start and run. But you can test by hooking the test light clamp to battery negative. Disconnect the ignition coil connector. Touch the pin of the connector (just make contact with the tip of the test light, don't jam it into the connector) for the brown with white stripe wire. Have someone turn the ignition key to on. It should light up for 3 secs or so.

Now to test the ground on ignition coil 3. With the ignition coil harness disconnected. Clamp the test light to battery positive. Touch the pin for dark blue with orange wire. Have someone turn the ignition to crank and crank for 5 secs. The test light should blink really fast.

If the test light blinks, we need to look at coil, plugs, wires. If it doesn't blink, we need to look at wiring, PCM.

Note: you can test the other ignition coils wires in the same way. This way you can compare coil 1 blinking to coil 3.

Note 2: Don't run your engine much with a cylinder (or two which is possible in this case) not igniting. This can pass unburnt fuel to the CATs which can ruin them.

Let us know how the testing goes.
carried it to the next step “I think”. Found pinout for pcm plug that controls #3 coil. With test clamp on pos bat terminal: pin 7 db/or does not light so no dead short between pcm and coil? Bad pcm?
 

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Nice work. Got a good idea where the problem is. Next step for me is to unplug the pcm connector. I’d try to do it without disturbing the harness. Re run the test and see if you still have the solid light.

Or you could do a wiggle test in the wire harness while you are doing the test and see if the light goes out.

Hope it’s not the pcm. I would think odds are against it shorting to power in the pcm. My guess is you have a short to power in the harness.
 

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Discussion Starter #10
Sequel, I appreciate all the help. tester clipped to pos bat terminal key off, pin 1 db/or of coil plug lights solid, unplug the above pictured pcm plug from pcm and tester light goes out, so no path to ground in my harness between coil plug and pcm plug? Plug pcm back up and tester light comes back on. Pcm?
 

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Sequel, I appreciate all the help. tester clipped to pos bat terminal key off, pin 1 db/or of coil plug lights solid, unplug the above pictured pcm plug from pcm and tester light goes out, so no path to ground in my harness between coil plug and pcm plug? Plug pcm back up and tester light comes back on. Pcm?
It’s looking like it’s the pcm. Before condemning any module you need to check powers and grounds. Unplug all connectors to the pcm. Grab the pin out that you have. You may have to grab the other connectors too. Use that test light and check all the grounds with the test light clamped to batt pos. Then check all the powers (even the keyed on ones) with the test light clamped to batt neg.

It’s a long shot but you want to be sure. Bad it’s the pcm, but at least it’s a conclusive diagnosis and not a wild guess.
 

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Discussion Starter #12
It’s looking like it’s the pcm. Before condemning any module you need to check powers and grounds. Unplug all connectors to the pcm. Grab the pin out that you have. You may have to grab the other connectors too. Use that test light and check all the grounds with the test light clamped to batt pos. Then check all the powers (even the keyed on ones) with the test light clamped to batt neg.

It’s a long shot but you want to be sure. Bad it’s the pcm, but at least it’s a conclusive diagnosis and not a wild guess.
Thank you so much for the shared knowledge. I wanted to "know" instead of going down the throw parts at it road. Will run those final tests. All the websites that offer refurb pcms have horrible reviews but its my DD so I will have to take a chance with the lesser of the evils. I will update which one I go with and if it works out.
 

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Discussion Starter #13
Quick update. All of my wiring checked out. Ordered a refurbished PCM from automotivediscounts on Ebay flashed with my VIN. Installed in 5 minutes. Jeep running like it was new again.
 

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Discussion Starter #15
I have no idea. I gave automotivediscounts (on Ebay) my VIN and they overnighted the PCM. I found 4-5 major websites that seemed to dominate the refurbished PCM market and they all had nightmarish comments in their reviews (some in the last few days). Took a chance with the Ebay guy simply because he had been selling PCMs for a while and no negative feedback. Bought SquareTrade warranty which should cover me if the PCM dies tomorrow.
 
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