Further inspection reveals something interesting.

The Haynes manual shows that California emissions should have a 20 amp fuse in the number 17 slot. The lid on the power distribution center says that I should have a 10 amp fuse in the number 16 slot.

What I actually have is a 15 amp in the number 16 slot.

Can anyone with an FSM confirm that the California emissions package is supposed to have a 20 amp fuse (would explain why it is popping a 15 amp)?

Can anyone run out to their WJ and tell me what size fuse your O2 sensor circuit is on?

 

You saved me hundreds from the dealer

After 5 weeks with the engine light on and replacing all 4 sensors and a relay I saw your post and checked the fuse. I didn't know to check earlier, I only used the autozone code check and then the key turn 3 times check to see what was wrong. Then your post mentioned fuse and I checked and it was bad. I had just made appt. With he dealer because I didn't know what else to do. You really did save me probably hundreds from the dealer. By the way it was a fifteen amp fuse. And the original cause was a melted wire touching the exhaust and shorting out. Good luck for you. Thanks again.

 

After 5 weeks with the engine light on and replacing all 4 sensors and a relay I saw your post and checked the fuse. I didn't know to check earlier, I only used the autozone code check and then the key turn 3 times check to see what was wrong. Then your post mentioned fuse and I checked and it was bad. I had just made appt. With he dealer because I didn't know what else to do. You really did save me probably hundreds from the dealer. By the way it was a fifteen amp fuse. And the original cause was a melted wire touching the exhaust and shorting out. Good luck for you. Thanks again.

Glad it helped you out :thumbsup:

Out of curiosity, do you remember which sensor had melted wires?

Every where I look in my 2004 service manual it shows a 15a fuse in slot 16 except for the deisel which is a 20a. I would start by disconnecting all the O2 senors, 4 of them, and turn the key on and see if the fues blows, maybe even start it. Check your wiring. Slot 16 is for the Auto Shutdown Relay.

Thank you for checking that - I am going to stick with the 15 amp fuse since it has worked fine for years until now, I just found it interesting that the discrepancy came up.

I may try disconnecting the sensors to see if it still blows, the only problem is that it takes about a week before it will blow the fuse. Intermittent problems suck to diagnose

I grabbed a multimeter and back-probed the fuse slot to watch the current while it was running. I had someone watch the output while I got under the Jeep and wiggled the harness for all four sensors and anything I could fine and could never make it get above 6 amps.

I think at this point I'm just going to order four new sensors and replace them. It's got 133k on it, so it probably won't hurt anyway.

 

Every where I look in my 2004 service manual it shows a 15a fuse in slot 16 except for the deisel which is a 20a. I would start by disconnecting all the O2 senors, 4 of them, and turn the key on and see if the fues blows, maybe even start it. Check your wiring. Slot 16 is for the Auto Shutdown Relay.

 

Ssdd

I have the exact same issue, 2004 4.0L JGC w/ 102k mi and the same three codes. My fuse is blown (BTW I only checked because of your post). Oddly enough it is a 15A rather than 10A as the cover diagram shows. I have 4 O2 sensors which I think signifies that it's a California emissions compliant vehicle as well. So for those of you with this issue, did the fuse + 4 O2 sensor replacement resolve this issue? No more engine light? Thanks - AJ

 

I tried disconnecting all four sensors and the fuse popped in about 1 sec. I'm guessing swapping the sensors won't get the root of the problem in this case.

 

Don't tell me that, I just ordered new sensors :rofl:

Mine doesn't pop very fast for some reason, it will stay off for about a week and suddenly pop again so maybe I'll get lucky and it will be in the sensor.

If you don't think it is your sensors, I would take a close look at the wiring harness that goes to the sensors. The only problem is that most of it is covered in wire loom so it may be tough to find a problem even if the problem is there.

My only other theory on this problem is that the wiring for the "ASD or CNG shutoff relay control circuit" as suggested by the P0136 code. I find it odd that this code comes up since the ASD circuit has its own fuse, so it seems like it should be separate from the O2 circuit.

The ASD fuse is slot 6 in this diagram

http://wjjeeps.com/misc/power_dist_ctr_02.jpg

by the way. I think I'm going to take a closer look at that circuit tonight, if I can find where the wires run....

Edit: If we can't get this problem figured out, I'll burn your Jeep down if you'll burn mine.

 

I've spent the last day or so peeling back loom and cleaning off wires. Every time I think I see a warn wire it turns out to be dirt.

In the back of my mind I wonder if it could be PCM related. I just replaced my Throttle Position Sensor a week or so ago. 6 months before it was the fuel injector in cylinder 6 (plus connector). The common pieces are the main wire harness and the PCM.

Hey if we meet in the middle there are some really deep lakes in KY...could be safer than burning.

 

I've spent the last day or so peeling back loom and cleaning off wires. Every time I think I see a warn wire it turns out to be dirt.

In the back of my mind I wonder if it could be PCM related. I just replaced my Throttle Position Sensor a week or so ago. 6 months before it was the fuel injector in cylinder 6 (plus connector). The common pieces are the main wire harness and the PCM.

Hey if we meet in the middle there are some really deep lakes in KY...could be safer than burning.

It's possible that it's PCM related but I really hope not. This has been the absolute first electrical issue I've had with my Jeep and I hope it will be the last - electricity is sneaky. I'd rather be replacing the engine than dealing with wiring

As far as the lakes....I've been needing a good fishing trip

Edit: I also know what you mean about thinking dirty wires are worn wires. I keep getting excited thinking I found the issue and then my heart just drops every time haha

Top of the motor, towards the back right of the valve cover near the rear firewall is a wiring loom that rests on a stud sticking out of the motor. This loom wears through from rubbing on that to the point of getting to the wires. Some of the wires are for the O2 sensors. They wear through and short out. I as well as many other people have had this problem. I am betting that this is your problem. I like found this out the hard way.

Let me know if this helps ya out.

I'm pretty sure I checked there because I remember seeing that wiring near the stud, but I will double check it :thumbsup::thumbsup:

 

Top of the motor, towards the back right of the valve cover near the rear firewall is a wiring loom that rests on a stud sticking out of the motor. This loom wears through from rubbing on that to the point of getting to the wires. Some of the wires are for the O2 sensors. They wear through and short out. I as well as many other people have had this problem. I am betting that this is your problem. I like found this out the hard way.

Let me know if this helps ya out.

 

On second thought, are you referring to the very large wire loom that hugs the back of the valve cover? If that's the one you were referring to maybe I'll go do a double-take on it....

 

I've been focusing my hunt on that big 1.5in (or so) bunch that drgonzo92 mentioned. I did find a schematic of this part of the electrical system and according to it our culprit should be orange with a dark green tracer.

It also looks like the ASD related code must show up because the power has to pass through that on the way to fuse #16 (and anything else of importance for fuel, air, or exhaust monitoring).

I'm also ruling out PCM for now because the circuit only connects to the PCM after the sensor. I could be wrong but that's the way it looks.

Starting to wonder what type of cost and effort it would take to swap out that whole wire harness. I think it's all one big sub assembly.

 

I actually think I just found it. I was looking at the wrong side after his post. There was a quarter size hole in the wire wrap at the back right side of the valve cover (when you are standing in front of the car facing the motor). I missed the wire the first 20 times I looked at that spot because of the way the wrap twists w/o moving the wires. It appears to be good to go when the wires are away from that stud. We'll see tomorrow once I drive it for a bit.

 

Hot damn, I felt under that big chunk of wiring harness and there is definitely a hole in the loom. I will be inspecting closer when I get back into Knoxville today but I'm also positive that's where the problem is.

I could hug you right now drgonzo:highfive:

 

Hot damn, I felt under that big chunk of wiring harness and there is definitely a hole in the loom. I will be inspecting closer when I get back into Knoxville today but I'm also positive that's where the problem is.

I could hug you right now drgonzo:highfive:

Glad to help. I found out the hard way with mine. Took awhile and was so frustrating. Hope this is the end to your troubles. And uh....... you Southerners with your hugging makes me nervous. I'll just accept the thankyou from here.

 

Thanks from the Midwest too! :2thumbsup:

 

Just to update, I got around to tearing apart that wiring harness today and, not surprisingly, found some melted insulation around a few wires. It's all patched up, fuse replaced, and no check engine so far. :thumbsup:

 

I have had code p0051 for the past few months on my 2004 Grand Cherokee. At first it was intermittent. light would come on and then go back off. Bought a Bosch sensor from Auto Zone, but the light came right back on. It has been on for several weeks and now I need to get the NC inspection done by the end of the month, so I have been trying to figure this out. Went out and bought the OEM sensor, BUT ...the light came right back on! Found this thread and checked the fuse. It was fine.
Got a flashlight and pulled the wiring look up, and the bolt had rubbed through the loom. Pulled it back on both sides to inspect the wiring but I could not find any wires with damage. Saw a few that had some scuffs on them, maybe that was enough to cause it to short? Taped it up good and pulled the loom up where it was not resting on the bolt. I may need to zip tie it or something to keep it off the bolt. Went on a 10 mile test drive and no light yet. Hopefully that takes care of it. Thanks for the heads up to check that loom, I would have never found that on my own.

 

I've had these same 3 codes on for 2 months now..

Replaced that blown fuse (#16) and all 4 02 sensors, and the code came right back on after 5 days of daily driving. Hopefully i will get some time tomorrow to check that loom where it rubs as you guys suggested.

So glad to find this post and hopefully that is my problem!! -Sick of getting worse mpg

 

Glad I found the time to dig into this, and really glad I found this post!!! Turns out that was exactly the issue.

Fixed the Orange and Dark Green wire, wrapped it all up good, put heater hose around that section, popped a new fuse in, and the codes haven't come back on yet! expecting a little better mileage now too...

Cheers

 

Has anyone with this problem had any problems with their engine acting like it is missing when accelerating or at a stop? Mine is acting like it is missing when I come to a stop light, but if I put it in neutral the idle will even out. But I am not getting any codes for misfires, but I am getting the P0031, P0051 and P0136. It is driving us nuts trying to find the problem. We have just had it in the shop to reinstall my camshaft position sensor and it is still not driving right. It does not like hills or stop lights.

 

did you change fuel filter lately it cuases all kinds of problems

Sent from my optimus

 

I could not tell you the last time it was changed. I feel stupid for not checking this. But I just find it strange that all my issues started after having my camshaft sensor removed and put back in. It was put in the shop for the camshaft sensor. Then everything else started.

 

I have been fighting the same issue with an 04, started running real rough and just dumping fuel into motor. So far we have replaced TPS, Cats, both front o2's (twice) and most recently the ECM. I did the ECM today and shut the light off. hasn't come back on yet but seems like it is still running rough.

 

I just bought an 04 WJ special edition. It runs fine but the check engine light is on. I'm getting p0031, p0051 and p0136. I have no symptoms and can't figure out what the problem is. The Chrysler dealership told me that i need a new PCM. I don't want to do that unless i absolutely have to. Any ideas??

 

now i think my 04 4.0 has the 4 o2 sensors but im not sure if it has ca emissions or not, it was purchased new in wv which has no emissions inspection, is there any way to determine if it does or does not, and is there any way i can modify it to 49 state

 

Sometime during the 04 model year the exhaust systems were changed from 2 minicats and a 3rd larger cat to 2 larger minicats only. There are still 2 O2 sensors for each minicat. It is a 50-state legal system.

 

I had the exact same problem I was throwing the same codes along with fuel injector open circuit and misfire codes....It was the loom that drgonzo92 was talking about. Put a vacuum cap or a piece of rubber hose over that stud to protect the wiring harness....

 

O2 Sensor wiring melted

I have a 2001 Jeep Grand Cherokee with a 4.0 California Emissions package (4 sensors). I had these same 3 codes, the blown O2 sensor fuse, and checked the wiring harness all looked good, even though I felt the dimple where it rested against the valve cover bolt. What mine ended up being was that someone had worked on my vehicle and replaced the oil pan. They poorly routed the 2/2 O2 sensor wiring, and I found it melted hard onto the exhaust pipe where it exited the catalytic convertor! I removed that o2 sensor, taped up the melted wiring, and viola!! ALL IS GOOD!! See someone else that posted a youtube video covering the EXACT same issue!

:cheers::cheers:

 

have the same codes as well as the fuse blowing out , but mine is a 04 GC 4.7, check the wiring cant seem to find anything need help getting this solved.
anybody run it to this on a v8? tips for solving?