Stalled up hill with check engine light P0351

J

jdp83

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Joined
Jan 2, 2020
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17
Location
TX
I bought my stock 04 Rubicon last Dec w/ 185k miles. It's been running fine around town but I've taken it out to a lease with some fairly steep (in my limited experience) off road hills and stalled it. I'm probably still learning to drive manual transmission, particularly in more challenging situations and didn't downshift enough so it bogged down and died a few times. The check engine light came on and is consistently reading just P0351 (Ignition Coil "A" Primary/Secondary Circuit). The first time I didn't have my scan tool with me and the light eventually went out on it's own a little bit later and read/cleared code when I got home. This weekend it happened a couple more times and captured freeze frames (below). First time I was in 2nd gear (2H) and it seemed better after restarting and clearing code. The last time I drove around slowly in 4L and I felt like I was losing power going up normal hill back to camp in 2nd (still 4L) and the CEL came on during climb but it kept running. It was kind of running rough at that point stuttering, maybe misfires. It seemed to get back to normal after restarting it.

According to my records the previous owner replaced valve cover gasket and spark plugs earlier in the year, Feb '19 at 175k. There was a prior note about exhaust system leaks and RMS leak in 2015 at 118k and no other documentation of fix. I took it to a shop for pre-buy checkout and they noted valve cover gasket may have been leaking, but it was also really dirty at the time or leftover from prior fix. I mentioned it was recently done and they said it was a crappy job, but just looks like a blue fel pro to me and I can't really tell. There is still an oil leak, which appears to be rear main seal to me, but haven't really looked too hard myself. They also noted replacing vacuum hoses (not sure which) and clean throttle body which I haven't done yet, but did replace most all fluids, belt, hoses, brakes.

Anyways, my concern with the code this last time is that it wasn't my fault driving. Unlike other descriptions I'm not seeing misfire codes being reported (maybe the first time, but don't recall and not the past couple I've saved),. Is it very common for just one coil to go bad? Should I see corresponding misfires logged? If it was the control signal, wouldn't I see a pair of cylinders fail together? A vacuum leak would likely effect all cylinders and not consistently the one? I've also never seen this around town (~14MPG), so it seems weird that it's only under this kind of load and I'm more curious about bigger problems like compression or exhaust leak. I'm debating taking it to a shop to look at before I tear into it, but they likely won't be able to reproduce the situation either. I could probably just replace coil pack myself cheaper than having them even look at it, but not sure if that's a good bet in this scenario.


From searching this seems to be good description:
https://repairpal.com/obd-ii-code-p0351

Mode $02 - Freeze Frame

PIDDescriptionValueUnits
0x02Freeze frame DTCP0351
0x03Fuel system 1 status2
0x03Fuel system 2 status2
0x04Calculated load value10.59%
0x05Engine coolant temperature195.8F
0x06Short term fuel % trim - Bank 1-4.69%
0x07Long term fuel % trim - Bank 15.47%
0x08Short term fuel % trim - Bank 24.69%
0x09Long term fuel % trim - Bank 24.69%
0x0BIntake manifold absolute pressure25.4inHg
0x0CEngine RPM640RPM
0x0DVehicle speed6.21MPH


Mode $02 - Freeze Frame

PIDDescriptionValueUnits
0x02Freeze frame DTCP0351
0x03Fuel system 1 status2
0x03Fuel system 2 status2
0x04Calculated load value16.08%
0x05Engine coolant temperature192.2F
0x06Short term fuel % trim - Bank 111.72%
0x07Long term fuel % trim - Bank 13.12%
0x08Short term fuel % trim - Bank 213.28%
0x09Long term fuel % trim - Bank 22.34%
0x0BIntake manifold absolute pressure12.7inHg
0x0CEngine RPM1984RPM
0x0DVehicle speed4.97MPH
 
PLEASE HELP, now I can't get it to crank!

Full story: This morning I proceeded to check coil pack and spark plugs. If I remember correctly, I measured .8, .8, and .9 ohms between pin 2 and the other pins of the plug for the primary coil. Between spark plug connectors 1&6, 2&5, and 3&4 I measure 1.6K ohms I believe (units may be off, but similar to whatever value I saw somewhere else). Spark plugs were a little brown for only 10k, but I don't really know. They are Champion 9034 and were gapped at .45, which is apparently how they come, I have since proceeded to close them down to .35 per sticker under hood. While I was doing this I wanted to do a compression test. Please let me know if I did something horribly wrong, but initially I only removed the first plug, took out the fuel pump relay and had my wife try to crank it, but wouldn't. I got in and turned it over a few times but didn't see anything on the compression gauge, she got back in and it wouldn't crank again. Hm, she's not used to the manual clutch, etc, and I thought it could be a bit weird to try to start so I told her to try harder (thinking she wasn't going all the way forward to start position), but still nothing. Skipping ahead, I'm wondering if we broke the ignition pin actuator.

Here's the rest of the troubleshooting in order as best as I can remember. I replaced the fuel pump fuse and removed the ASD relay instead. At some point I did take out the rest of spark plugs. I've moved the clutch interlock bypass fuse to alleviate that requirement. I added a battery boost jumper just in case battery was getting low, but I think it stayed above 12.2V at least, at some point 14.4V was applied from battery pack. At this point after repetitively trying to start I saw codes on dash showing the P1388 and P1282 codes referring to the ASD relay and fuel pump relay control circuit respectively. Interestingly these did not show up in my scan tool, just the original P0351, and I proceeded to clear them all. I started putting things back together, hooked up coil thinking it needed to see it electrically and tried starting with coils attached but no plugs (was this bad?). Replaced plugs and reinstalled coil and now it's still not cranking. Removed battery for a min to try to reset PCM, but now realize this may not be the full reset procedure. Now I'm bummed and trying to figure what harm I did and starting from scratch researching no crank issues. That's when I stumbled upon the ignition pin problem other have faces. Curious to rule out the starter, relay, etc. I went back out, removed starter relay and jumped the 2 relay pins and it turns over, but doesn't start. Also tried swapping horn relay in and didn't work either. I had my wife inside with the key turned to run position, when I come back dash just says check gauges and not the engine light. Had clutch in and also bypassed again. At this point if key is really in run, shouldn't it have possibly started (did I mess something up coil or spark plug wise in addition to ignition pin?) or is there still some other security mechanism (I have gray SKIM key). Is this enough to confirm I need ignition actuator? Did I somehow fry PCM with my sequences above? I don't think there's any codes stored, but I'll go double check.
 
I doubt you've fried the PCM or anything.

You've already confirmed the starter isn't the issue. From there you'll want to work backwards along the ignition wire to the relays and to the steering column.

The relays are interchangeable. Swap them with any other relay in the PDC that looks the same and try again. When the key is turned to start, the starter relay shouldn't least click. If it doesn't, there is an issue with the relay or further upstream. You can jump the relays manually with a piece of wire (stick it in socket 30 and 87) for testing purposes.

There is a clutch interlock that requires the clutch to be depressed when starting the car. This can sometimes fail. With the Rubicon models only, the interlock is bypassed in 4-Low. If shifting into 4-Low doesn't change anything, then that's probably not the issue. The clutch interlock bypass fuse does nothing in a Rubicon.

Just be aware the vehicle will start in gear if the clutch isn't depressed and the shifter is in gear, and it will automatically begin to roll. In the lowest gears, the brakes may not be powerful enough to stall the engine.

A very common cause of multiple random issues is bad grounding and bad battery connections. Make sure every contacting connection is tight and shiny. Disassemble the terminals and use steel wool to clean up any contacting surfaces on the terminals, the posts, and the ring terminals. Also clean the grounds where they meet the body and the engine block. The engine block ground is notorious for causing issues.

In addition, be sure to download the factory service manual and take a look at the wiring diagrams if you get stumped. The FSM will identify every wire, splice, connector, and component in the Jeep.
I recommend opening it on a tablet or computer if possible.
https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/
FYI, you can read trouble codes simply by rocking the ignition back between accessory and run 3 times (without starting). The codes will display in the odometer one by one. May save a bit of effort with an OBDII reader.
 
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The Factory Service Manual has detailed troubleshooting steps to help you fix P0351. I'd download the FSM from here

Factory Service Manual

and search for P0351. Next time I'd start there first. At this point it couldn't hurt to put everything back the best you can and do the tests with the test light and see where you are. Obviously you aren't going to be able to activate the ASD relay with the DRB but you should be able do everything else. I think bridging that relay without the DRB is pretty easy if you need to. The FSM might also help you with the new codes, the general code descriptions on the internet aren't always helpful.
 
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Thanks for the responses, I needed some positive encouragement. I forgot I had downloaded the FSM and looking back I see it does walk through some troubleshooting steps, I'll go back and check more thoroughly. But ultimately it's intermittent under specific load I can't easily reproduce at home and trying to understand other contributing factors. I mean, normally it runs fine on all cylinders, with no misfires, so obviously power is getting to all the places a 12V test light would check. The primary coil resistance measurements are slightly different (.53-.63 ohm) than I measure (.8 and .9 ohm) and saw (.71-.88 ohm - https://www.cherokeeforum.com/f2/testing-coil-rail-204328/#post3010550 actually, just found it lists this spec elsewhere in FSM), but it doesn't seem to say exactly how/where to measure. I thought pin 2, up from bottom with connector to left, was common (see cherokee forum link), and got fairly consistent measurements, but if pin 1 was common it was much diff. I have also since noticed hoses cracked around the PVC elbows, or rather crankcase vent tubes, is that enough to cause a vacuum leak and this issue?

In addition to compression test I was going to do a fuel pressure test, however I think I'd expect low pressure to effect other cylinders. Ultimately trying to rebuild some confidence in common failing components to minimize chances of getting stuck out in the woods. I also plan to clean throttle body/intake.

At this point I have put it all back together, no codes, and can't crank, so need to get back to tracing ignition circuits later this afternoon to confirm before ordering ignition switch actuator pin assuming I broke it in the process. Just wanting to confirm there's no other potential security things in place to reset after removing fuses or other potential damages I could have done to make it worse than I started (it was running around town just fine).
 
A broken actuator pin was pretty obvious on mine. The key moved very easily and did not snap into any position well. The key would feel very different as you turned it. It could be the switch but I doubt it's the pin.
 
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I just jumped both the ASD and (temporarily) starter relay and it cranks and starts up just fine and runs as long as I hold the pliers in ASD holes. So you think I'd need the switch as well? Just trying to figure out what to go ahead and order if I can't find it locally after I tear into it.

After my wife tried to start it and I said try harder, the key was stuck kind in the start position and had to jiggle it back out, so that's probably when damage occurred, just not sure what exactly. I do still feel the springy resistance going from run to start.
 
jdp83 said:
I do still feel the springy resistance going from run to start.
Click to expand...
That normally means the pin isn't broken. I don't know if your switch is broken, the key/pin/switch assembly has little springs and do-dads that can get all jammed up. I used this video to take mine apart. You need a special t10 anti-tamper bit. Grainger sells them individually pretty cheap if you have one nearby.

Ignition Actuator Replacement
 
I got the ignition back together after replacing the switch and went ahead and did the actuator pin before I put it all back together. After the hassle of various compression gauges and concerns otherwise I've concluded I have good compression in all cylinders (165-180psi), the 1st is prob lowest of them, but not by much and didn't seem to increase more than maybe 5psi "wet" either.

Other than closing the gap on spark plugs from .045 to .035 I've yet do do much in regards to the original P0351 problem. I wasn't able to disconnect fuel line from fuel rail with plastic tool to test pressure, so gave up on that for now. I figured a fuel pressure problem should've affected more cylinders, it always starts up good, and seemed to repressurize quickly no problems. By the way, tank has been at least 1/2 when it happened. I'm planning on cleaning throttle body next (removing it) and repairing PCV/crank case vent tubes. I did notice a vacuum hose easily pulled loose and pushed it all the way back in near evap system/fuel lines and otherwise poked around with propane without much effect. Should I go ahead and replace coil pack w/ a $60 one from Amazon (in other words does brand matter much for this)?

I might do a seafoam treatment in the fall before I change oil. It was changed when I got it last Dec. and leak seems to have mostly stopped lately. Any other thoughts?
 
Seafoam directly through the throttle body is a good way to get rid of carbon deposits. I've done it on numerous cars with good effect. Makes a lot of smoke, but cleans it out pretty well. In the gas tank, it is next to useless. In the crankcase it can dissolve some deposits.

Once you get it running again, be sure to run it hard. One of the most effective ways to prevent carbon buildup is to run the engine fast and hard. Get on the freeway and floor it all the way up to redline before you shift. If you can find a big hill to run full throttle and 4000-5000 RPM up, do that. The excess heat and vibration will quickly clean up the engine. (Manufacturers often recommend to rev up the engine at least once per drive cycle in a lot of vehicles to prevent carbon buildup.)

pagrey said:
Skip seafoam. Maybe Techron in the gas tank or just use a tank or two of Chevron but I would skip seafoam.
Click to expand...

It's a really good idea to use any formulation of Top Tier gas, which includes Chevron and a lot of other brands. Top Tier is a voluntary standard agreed to by certain gas companies and automakers. Almost all automakers recommend Top Tier. The TJ FSM was created before Top Tier, but it explicitly calls out a similar previous standard.

Any of the stations on this list subject themselves to the standard:
https://www.toptiergas.com/licensed-brands/
The extra detergents in these gasolines is effective at removing and preventing carbon buildup on valves, heads, and pistons. I've attached some independent research that verifies this claim.
 

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