Two PCM drivers went out?

J

justfixedthat...

TJ Enthusiast
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Texas
I removed the valve cover to get to the springs and for laughs I also snapped off the PCV valve while working on the catch can. Bolted everything back up to drive to O'reilly. It clearly wasn't running all 6 cylinders, was shooting oil out of a place that, well, was already leaking a little but damn it was really flowing (there is a dark line from my driveway to O'reilly), and gave codes for 'cylinder 6 injector circuit open' and a misfire in 6 obviously. Oh and I had assumed the exhaust flange needed a gasket because it sounds like a diesel but apparently the connection between the exhaust pipe and manifold has a hole. I found that out because it got louder.

I first thought it was increased crankcase pressure forcing the oil out, but that would only make sense if the PCV valve was actually installed and wasn't breathing right - there was just a hole at the moment. Drove back, installed the valve, didn't make a difference. I swapped the plugs for injectors 5 and 6 to see if it was 6's plug or the injector itself, then it gave codes for 5 and 6 'injector circuit open'. Switched them back and both codes stayed. So, 5 is bad now too. Thinking that 4 must be ok, I switched plugs 4 and 5 to see if maybe 5 would act right. No change and no code for 4. Put in new 5 and 6 injectors. No change.

Anyway, wires were good at both ends (from injectors to PCM). No rubbing, no ground, voltage was even to all 6 injectors. However, when testing the wires coming out of the PCM, there was no pulse. Driver's weren't communicating with the injectors. When I unplug injectors 4, 5 and 6 there is no change in idle. The IAC doesn't compensate at all.

My idle vacuum is down from 15 to 10, presumably because I'm running on 3 cylinders.

I used rope in the spark plug ports while changing the springs so, maybe a couple of them didn't thread right?

Maybe I... I got nothing other than it's the PCM (I've only had it 3 years)

Any advice guys?
 
Was the engine running properly before you removed the valve cover?

What error codes are/were stored?
 
I had been getting misfire codes a few years ago on the highway. Since then I've kept it under 55mph and I haven't had any codes since then. Take that back - a few months back my neutral safety switch went out. I rebuilt my starter and I was bypassing the switch for a while. I put in a new switch a week ago and it started fine. Other than than incident yes it was running great. i took the cover off, replaced the PCV valve, and I had the spark plugs out (didn't replace them, but had them out).
 
Well if it was running fine before you did this, that seems to suggest that what you did ended up causing these codes. I'm not sure what would have caused it, but I'm pretty sure that driving your TJ around with it blowing oil all over the engine is probably enough to cause some codes, guaranteed.

I'm not sure I'd chalk this up to the PCM, I'd chalk it up to oil having potentially gotten all over a bunch of stuff and ruined it.
 
Well the oil had been dripping from one of the hoses running from my oil filter adapter to the remote oil filters, so the only thing getting oil in it was the exhaust pipe below the stock oil filter location and my mouth while fixing it. It started 'blowing' oil out of that same spot after putting the cover/new PCV on.
 
First thing I would now suggest is to check the coil rail and make sure the boots are actually seated on the plugs. Also check the connector for the coil rail since it was moved.

If it's not the coil rail to spark plugs, I think you have a short in the wiring harness someplace. You may need to remove the valve cover again and open up the loom for a thorough inspection of the wiring from the injectors all the way back to the passenger side of the valve cover.
 
And I had assumed that I must have knocked something loose, but I took off the tape/looming and the wires tested good. That's why I was wondering whether the 5 and 6 spark plugs didn't threat right or got dirty while going in, and that is perhaps preventing the PCM from communicating with the injectors.
 
AjRagno said:
First thing I would now suggest is to check the coil rail and make sure the boots are actually seated on the plugs. Also check the connector for the coil rail since it was moved.

If it's not the coil rail to spark plugs, I think you have a short in the wiring harness someplace. You may need to remove the valve cover again and open up the loom for a thorough inspection of the wiring from the injectors all the way back to the passenger side of the valve cover.
Click to expand...
Beat you to it
 
But they're all getting power. And injectors 5 and 6 are new. The codes are 0205 and 0206, which I think come from upstream at the PCM. And when I test the wires right at the PCM, the driver's aren't pulsing. Oddly there are no codes for #4 even though I can unplug the #4 boot while it's running with no change in idle so it's clearly not working either.
 
My mistake. I saw "rail" and flew past everything else, thinking of the fuel rail.

So a boot not seated right could be telling the computer not to send a signal to that injector?
 
justfixedthat... said:
My mistake. I saw "rail" and flew past everything else, thinking of the fuel rail.

So a boot not seated right could be telling the computer not to send a signal to that injector?
Click to expand...

Yes. If the fuel injectors are not functioning, either the wiring for the injectors is damaged or the PCM is shutting the injectors off to avoid engine damage. It's unlikely that the PCM randomly failed just after you performed this recent work.

I don't have reference for it at the moment, but I believe the PCM will turn off the injector(s) if a coil fails. It may also turn off an injector if the 02 sensor detects raw fuel being dumped into the cat.
 
justfixedthat... said:
"I believe the PCM will turn off the injector(s) if a coil fails"

That is the exact information I was looking for. Thank you.
Click to expand...
justfixedthat... said:
"I believe the PCM will turn off the injector(s) if a coil fails"

That is the exact information I was looking for. Thank you.
Click to expand...
Hey, just saw this thread too after replying in the other one. Keep in mind that the ignition coil assembly has 3 coils, not 6. Each coil services 2 plugs/cylinders. If a coil is bad, it will affect both cylinders it services. Look up the pairs to be sure, but I think I recall them being 1/6, 2/5, and 3/4.
 
justfixedthat... said:
I removed the valve cover to get to the springs and for laughs I also snapped off the PCV valve while working on the catch can. Bolted everything back up to drive to O'reilly. It clearly wasn't running all 6 cylinders, was shooting oil out of a place that, well, was already leaking a little but damn it was really flowing (there is a dark line from my driveway to O'reilly), and gave codes for 'cylinder 6 injector circuit open' and a misfire in 6 obviously. Oh and I had assumed the exhaust flange needed a gasket because it sounds like a diesel but apparently the connection between the exhaust pipe and manifold has a hole. I found that out because it got louder.

I first thought it was increased crankcase pressure forcing the oil out, but that would only make sense if the PCV valve was actually installed and wasn't breathing right - there was just a hole at the moment. Drove back, installed the valve, didn't make a difference. I swapped the plugs for injectors 5 and 6 to see if it was 6's plug or the injector itself, then it gave codes for 5 and 6 'injector circuit open'. Switched them back and both codes stayed. So, 5 is bad now too. Thinking that 4 must be ok, I switched plugs 4 and 5 to see if maybe 5 would act right. No change and no code for 4. Put in new 5 and 6 injectors. No change.

Anyway, wires were good at both ends (from injectors to PCM). No rubbing, no ground, voltage was even to all 6 injectors. However, when testing the wires coming out of the PCM, there was no pulse. Driver's weren't communicating with the injectors. When I unplug injectors 4, 5 and 6 there is no change in idle. The IAC doesn't compensate at all.

My idle vacuum is down from 15 to 10, presumably because I'm running on 3 cylinders.

I used rope in the spark plug ports while changing the springs so, maybe a couple of them didn't thread right?

Maybe I... I got nothing other than it's the PCM (I've only had it 3 years)

Any advice guys?
Click to expand...
if you don't have Wranglerfix on this thread you need to get him on here he is familiar with all things PCM.
 
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Reactions: mots
mots said:
Hey, just saw this thread too after replying in the other one. Keep in mind that the ignition coil assembly has 3 coils, not 6. Each coil services 2 plugs/cylinders. If a coil is bad, it will affect both cylinders it services. Look up the pairs to be sure, but I think I recall them being 1/6, 2/5, and 3/4.
Click to expand...

I didn't mean to suggest that he had a bad coil pack, only that the PCM can shut down injectors for a couple of reasons. I think his coil pack is good, otherwise bank 1 would also be affected. Simplest explanation here is that the coil boot for #5 and/or #6 is not seated on the spark plug.
 
AjRagno said:
I didn't mean to suggest that he had a bad coil pack, only that the PCM can shut down injectors for a couple of reasons. I think his coil pack is good, otherwise bank 1 would also be affected. Simplest explanation here is that the coil boot for #5 and/or #6 is not seated on the spark plug.
Click to expand...
Yeah, I understand. I was just making sure he was aware of how the coils work when troubleshooting.

However, the codes he is getting would not suggest the ignition side is the problem. As I told him in the other thread, the codes P0205 and P0206 "Injector Circuit Malfunction'" are definitely because of a problem detected by the PCM on those two particular injector circuits (injector, connector, wiring to PCM, or PCM circuitry itself).
 
mots said:
Hey, just saw this thread too after replying in the other one. Keep in mind that the ignition coil assembly has 3 coils, not 6. Each coil services 2 plugs/cylinders. If a coil is bad, it will affect both cylinders it services. Look up the pairs to be sure, but I think I recall them being 1/6, 2/5, and 3/4.
Click to expand...
That's a good point. I installed a new coil pack to be sure it wasn't the boots. No change so I put my old one back in.
 
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