Limp Mode and 4WD Issues

[bigcheeshead]

The purpose of this thread is try and get an edumacated guess on what could’ve caused the problem described below and ways to prevent it from happening again. Please do not use this thread to rant about how good/bad Jeep is or the merits of where we should or shouldn’t take our Jeeps to or any other opinions. Let’s keep this thread technical please!

So, I was off-roading yesterday and got to experience limp mode on top of the mountain that scared the living #$&^ out of me. While climbing a rocky mountain trail in my JT Rubicon at about 20 degrees incline, at around 4,500 elevation in 4L with rear lockers on (trail was pretty washed out) all of a sudden:
A. Engine started to sound really loud and bad
B. Service 4WD, Service Sway Bar Disconnect & service lockers messages came on.
C. There was a really nasty burned oil kind of smell that lasted for about 30 seconds
D. Jeep slowed down to 2 miles/hour struggling to drive up.

This happened in about 75 degrees ambient temperature and none of the gauges showed anything overheating. I did not check what the RPM was, it was in auto and not manual though. I drove like that for about 5 minutes until I got to the top. Once at the top I noticed that I couldn’t move the clutch from 4L up. I turned the Jeep off, waited about a minute and turned it back on. Everything went back to normal. We ran two different OBD II scanners and none showed any codes after the Jeep was restarted, yes, we scanned it without the engine running. I was able to drive down for about 45 minutes in 4L without issues.

The first two things I’m going to do are:

1. Replace the cold air intake system with K&N aftermarket one with a reusable air filter that I can wash every couple of months. Jeep is currently at 24,000 miles and I have not replaced the air filter yet. I’m off-roading nearly every weekend in Arizona dusty environment and that filter is freaking dirty at the moment.

2. Change my diff fluids for both front and rear. I’ve replaced them once already around 12,000 miles 8 months ago but figure it wouldn’t hurt if gears are overheating. I will also visually expect the gears for any damage.

Obviously, I can’t take it to a dealer since there are no codes and I haven’t been able to reproduce it again while light wheeling all day today. I’ve also checked everything underneath and nothing is leaking nor are there any obvious damages that I can tell. All fluid levels are normal as well. Any other suggestions?

Jeep is JT 2020 Gladiator Rubicon 3.6 V6 gas, 4.5 inch lift with 37 inch tires. It also weights around 1,000 pounds over the curb weight due to aftermarket parts. Running stock gear ratio as well.

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[ShadowsPapa]

1. Replace the cold air intake system with K&N aftermarket one with a reusable air filter that I can wash every couple of months. Jeep is currently at 24,000 miles and I have not replaced the air filter yet. I’m off-roading nearly every weekend in Arizona dusty environment and that filter is freaking dirty at the moment.

If you like your engine, that's the worst filter on the market. Scientific dyno testing proves it. They let in more dust and dirt, and actually fill and restrict sooner than almost any other filter.
If the air is really that dusty, it's the worst move you can make.

I replaced my air filter at about 19,000 miles, it was filthy, and I live in Iowa, don't off-road with it.
Simply use quality paper filters and change more often. It'll save your engine.
If mine was that filthy after under 20K miles, I can't see how you didn't change it sooner in the AZ dust. I've been there during dust storms.

Are you on stock 4.10 gears? with 37s? Sorry if I missed where you mentioned replacing the gears, allergies are really killing my eyes and they are totally foggy tonight.

Total dirt passed through the filters during testing -

Filter efficiency test - (an ISO test) - K&N is the worst of those tested -

And the dirt capacity - K&N can't hold much dirt -

 

[Rvalas]

going to sound silly but it sounds like you need a catch can, were you white smoking before it went into limp mode? If so it was oil getting into the valves. I have not seen limp mode but I have had mine at too steep an angle and a catch can fixed it.

 

[bigcheeshead]

One other thing worth noting is that I've experienced what felt l

going to sound silly but it sounds like you need a catch can, were you white smoking before it went into limp mode? If so it was oil getting into the valves. I have not seen limp mode but I have had mine at too steep an angle and a catch can fixed it.

No white smoke at all. I'm well familiar with the oil issues you're describing on steep obstacles. This was definitely different.

 

[Rvalas]

One other thing worth noting is that I've experienced what felt l

No white smoke at all. I'm well familiar with the oil issues you're describing on steep obstacles. This was definitely different.

Hrm another thing to look for are loose wire looms, if you have done work to your JT, you might have forgotten to, or had a loom come loose and while at the steep incline you may have got it too hot and the smell could have been burning loom/shield. Not saying you melted a wire but you might have gotten it hot enough to induce resistance to the commbus which is really sensitive.

What you are describing is what happened to my GMC when I had a weird grounding issue kicking my body control module offline it would go into limp mode just driving down the highway.

 

[dcmdon]

The purpose of this thread is try and get an edumacated guess on what could’ve caused the problem described below and ways to prevent it from happening again. Please do not use this thread to rant about how good/bad Jeep is or the merits of where we should or shouldn’t take our Jeeps to or any other opinions. Let’s keep this thread technical please!

So, I was off-roading yesterday and got to experience limp mode on top of the mountain that scared the living #$&^ out of me. While climbing a rocky mountain trail in my JT Rubicon at about 20 degrees incline, at around 4,500 elevation in 4L with rear lockers on (trail was pretty washed out) all of a sudden:
A. Engine started to sound really loud and bad
B. Service 4WD, Service Sway Bar Disconnect & service lockers messages came on.
C. There was a really nasty burned oil kind of smell that lasted for about 30 seconds
D. Jeep slowed down to 2 miles/hour struggling to drive up.

This happened in about 75 degrees ambient temperature and none of the gauges showed anything overheating. I did not check what the RPM was, it was in auto and not manual though. I drove like that for about 5 minutes until I got to the top. Once at the top I noticed that I couldn’t move the clutch from 4L up. I turned the Jeep off, waited about a minute and turned it back on. Everything went back to normal. We ran two different OBD II scanners and none showed any codes after the Jeep was restarted, yes, we scanned it without the engine running. I was able to drive down for about 45 minutes in 4L without issues.

The first two things I’m going to do are:

1. Replace the cold air intake system with K&N aftermarket one with a reusable air filter that I can wash every couple of months. Jeep is currently at 24,000 miles and I have not replaced the air filter yet. I’m off-roading nearly every weekend in Arizona dusty environment and that filter is freaking dirty at the moment.

2. Change my diff fluids for both front and rear. I’ve replaced them once already around 12,000 miles 8 months ago but figure it wouldn’t hurt if gears are overheating. I will also visually expect the gears for any damage.

Obviously, I can’t take it to a dealer since there are no codes and I haven’t been able to reproduce it again while light wheeling all day today. I’ve also checked everything underneath and nothing is leaking nor are there any obvious damages that I can tell. All fluid levels are normal as well. Any other suggestions?

Jeep is JT 2020 Gladiator Rubicon 3.6 V6 gas, 4.5 inch lift with 37 inch tires. It also weights around 1,000 pounds over the curb weight due to aftermarket parts. Running stock gear ratio as well.

I'm sorry to hear about your problem. But I can just about guarantee that the things you are planning to do won't impact this problem.

1) a dirty filter isn't going to cause any short term problems. Don't forget that 99% of the time your throttle plate is blocking most of the intake.

2) Gears are less likely to overheat locked crawling around off road than they are to at 70 mph on the highway.

 

[jmccorm]

We ran two different OBD II scanners and none showed any codes after the Jeep was restarted, yes, we scanned it without the engine running. [ ... ]

Obviously, I can’t take it to a dealer since there are no codes and I haven’t been able to reproduce it again while light wheeling all day today.

This may or may not apply to you:

There are two different types of codes you should be aware of. There are the CEL codes (your Check Engine Light codes) which are picked up by common OBD-II scanners. Beyond that, each of your vehicle's modules store their own per-module trouble codes. An everyday OBD-II scanner won't pull those. If you want to see those, you'd need something designed to do it. (And if you do, DO NOT CLEAR THEM.)

But the underlying point here is that just because your OBD-II scanner did not record a code does not mean that one or more of your modules may have recorded evidence that the dealer can use to substantiate your issue.

As a reminder, if you are having a weird issue, always try to remember to record some video of it. Dealers love it when you can show them something is wrong even if you're giving them a vehicle where everything looks right.

Unless you're sure your modules recorded nothing, if you're under warranty, I'd take the issue to your dealer. Even if you're afraid they'll find nothing.

 

[bigcheeshead]

going to sound silly but it sounds like you need a catch can, were you white smoking before it went into limp mode? If so it was oil getting into the valves. I have not seen limp mode but I have had mine at too steep an angle and a catch can fixed it.

Stock gear ratio and thanks for digging up the filter comparison above. Will have to do more research I guess.

 

[bigcheeshead]

This may or may not apply to you:

There are two different types of codes you should be aware of. There are the CEL codes (your Check Engine Light codes) which are picked up by common OBD-II scanners. Beyond that, each of your vehicle's modules store their own per-module trouble codes. An everyday OBD-II scanner won't pull those. If you want to see those, you'd need something designed to do it. (And if you do, DO NOT CLEAR THEM.)

But the underlying point here is that just because your OBD-II scanner did not record a code does not mean that one or more of your modules may have recorded evidence that the dealer can use to substantiate your issue.

As a reminder, if you are having a weird issue, always try to remember to record some video of it. Dealers love it when you can show them something is wrong even if you're giving them a vehicle where everything looks right.

Unless you're sure your modules recorded nothing, if you're under warranty, I'd take the issue to your dealer. Even if you're afraid they'll find nothing.

All good points! Although with adrenaline rushing, digging for my cellphone to record it was the least of my concerns at that moment

 

[DocMike]

You drop off a big rock too fast?
Mine went into limp and the rear brakes locked up on Redcone.
I think I may have set off a collision sensor. I finished the trail and nursed it to a town where I cleared codes with Tazer. I was holding up a 1980s VW bus on the road. That was the level of my power loss.

One other thing worth noting is that I've experienced what felt l

No white smoke at all. I'm well familiar with the oil issues you're describing on steep obstacles. This was definitely different.

 

[bigcheeshead]

I'm sorry to hear about your problem. But I can just about guarantee that the things you are planning to do won't impact this problem.

1) a dirty filter isn't going to cause any short term problems. Don't forget that 99% of the time your throttle plate is blocking most of the intake.

2) Gears are less likely to overheat locked crawling around off road than they are to at 70 mph on the highway.

Hmm, so if not the two above then what?

 

[Renegade]

The service 4WD messages could result from broken wheel speed sensor wires, broken FAD wiring or actuator, damaged transfer case, or even a broken axle shaft. Were you stationary when trying to shift the t-case? (You said “clutch”, but I assume you meant the shifter)
Also, there are times when the Jeep’s traction control system will cut power and/or apply the brakes while climbing a very hard obstacle. Using Off Road + mode in 4Lo helps prevent that.

 

[bigcheeshead]

The service 4WD messages could result from broken wheel speed sensor wires, broken FAD wiring or actuator, damaged transfer case, or even a broken axle shaft. Were you stationary when trying to shift the t-case? (You said “clutch”, but I assume you meant the shifter)
Also, there are times when the Jeep’s traction control system will cut power and/or apply the brakes while climbing a very hard obstacle. Using Off Road + mode in 4Lo helps prevent that.

Yes, I did meant the shifter and yes I was stationary. Wouldn't any of the causes you've mentioned with wiring, damaged transfer case etc... persisted instead of completely disappearing after power off/on cycle?

 

[Renegade]

Yes, I did meant the shifter and yes I was stationary. Wouldn't any of the causes you've mentioned with wiring, damaged transfer case etc... persisted instead of completely disappearing after power off/on cycle?

The t-case often won’t shift at all when stationary. If a wiring harness was pulled tight when the suspension articulated, it may have caused a momentary loss of continuity. It’s also possible that a locker actuator or the FAD disengaged, and the system detected some speed differentials it didn’t expect. When out of parameter specs are detected, it will throw the service 4WD system warning, and maybe others. I stretched a front wheel speed sensor wire and broke an axle shaft at the same time, and then I couldn’t even get the rear locker to work because the system basically shuts down.

 

[ShadowsPapa]

This may or may not apply to you:

There are two different types of codes you should be aware of. There are the CEL codes (your Check Engine Light codes) which are picked up by common OBD-II scanners. Beyond that, each of your vehicle's modules store their own per-module trouble codes. An everyday OBD-II scanner won't pull those. If you want to see those, you'd need something designed to do it. (And if you do, DO NOT CLEAR THEM.)

But the underlying point here is that just because your OBD-II scanner did not record a code does not mean that one or more of your modules may have recorded evidence that the dealer can use to substantiate your issue.

As a reminder, if you are having a weird issue, always try to remember to record some video of it. Dealers love it when you can show them something is wrong even if you're giving them a vehicle where everything looks right.

Unless you're sure your modules recorded nothing, if you're under warranty, I'd take the issue to your dealer. Even if you're afraid they'll find nothing.

And some problems are transient and don't request a CEL trigger -
Even misfires that cause the engine to buck won't always trigger a light or save a code.

This, for example, never triggered a light, no warning and when I got to the dealer with it, it had not only settled down, there were no codes inside! If I hadn't checked it myself, logging things while running and driving it, then printing the log, they'd have never figured it out.

I handed them a multi-page printout of all readings at the time of the misfires, but nothing was stored.


Error code: P0303
Cylinder 3 ignition failures
Test not complete
Error intermittent
Error warning lamp not requested
CARB Freeze Frame:
___________________
Fault code: P0303
PCM Mileage since MIL On: 0.00 miles
PCM Odometer: 950.27 miles
Open Loop - Bank 1: No
Closed Loop - Bank 1: Yes
Open Loop due to Driving Conditions - Bank 1: No
Open Loop with DTC - Bank 1: No
Closed Loop with DTC - Bank 1: No
Open Loop - Bank 2: No
Closed Loop - Bank 2: No
Open Loop due to Driving Conditions - Bank 2: No
Open Loop with DTC - Bank 2: No
Closed Loop with DTC - Bank 2: No
Engine load: 30.20 %
Freeze Frame Engine Coolant Temp: 66.00 Deg.C
Intake Air Temperature: 215.00 Deg.C
Ambient Air Temperature: 12.00 Deg.C
Short Term Fuel Trim - Bank 1: 12.49 %
Long Term Fuel Trim - Bank 1: -3.13 %
Short Term Fuel Trim - Bank 2: 9.37 %
Long Term Fuel Trim - Bank 2: -7.04 %
MAP Voltage: 1.96 V
(and it goes on for several more lines but showed most engine conditions at the time of the events, multiple events over pages)

Dealers love it when you can show them something is wrong even if you're giving them a vehicle where everything looks right.

You should have seen the looks on their faces - like "where did you get this??!!" and one of them actually came over to me and asked directly - how did you get this? Normally we are the only ones to see this detail.
But they were glad I had provided it. Their looks were priceless.

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