JK traction control issue

1stDeuce

Explorer
You are indeed getting into stability control. Centering the steering wheel may help, but it should learn zero anyway when you fire it up and begin driving.

By chance have you had a dealer program your Jeep with the actual tire size you are running? If you're running larger than stock tires, there will be a discrepancy between the speed you are going, and the speed that stability control thinks you are going. When you turn, stability control monitors a yaw rate sensor and compares that to what it calculates that the yaw rate should be based on steering angle and speed. With a higher than indicated speed due to larger tires, stability control can start to believe that you are starting to spin out due to the calculated yaw rate being lower than the sensor is reading. This would cause it to cut power, and activate and drag the brakes on the outside of the turn.

If the tire size is correct, it is also a possibility that there's just a perfect combination of things where the sensors are fooled into zeroing when they shouldn't, and that particular curve gets just a little past the threshold for activation.

I would wager it'll go away if you get the correct tire size in there though. That's a big one. AEV Procal can do this for you, as can many aftermarket programmers. If you're friends with the dealership, they can do it too. You need the computer to share the correct tire size with the ABS unit that runs stability/traction control.

(I didn't do your JK, but I did traction/stability/abs development for many other vehicles when I worked for TRW, in a past life...)
 

ventura911

Adventurer
You are indeed getting into stability control. Centering the steering wheel may help, but it should learn zero anyway when you fire it up and begin driving.

By chance have you had a dealer program your Jeep with the actual tire size you are running? If you're running larger than stock tires, there will be a discrepancy between the speed you are going, and the speed that stability control thinks you are going. When you turn, stability control monitors a yaw rate sensor and compares that to what it calculates that the yaw rate should be based on steering angle and speed. With a higher than indicated speed due to larger tires, stability control can start to believe that you are starting to spin out due to the calculated yaw rate being lower than the sensor is reading. This would cause it to cut power, and activate and drag the brakes on the outside of the turn.

If the tire size is correct, it is also a possibility that there's just a perfect combination of things where the sensors are fooled into zeroing when they shouldn't, and that particular curve gets just a little past the threshold for activation.

I would wager it'll go away if you get the correct tire size in there though. That's a big one. AEV Procal can do this for you, as can many aftermarket programmers. If you're friends with the dealership, they can do it too. You need the computer to share the correct tire size with the ABS unit that runs stability/traction control.

(I didn't do your JK, but I did traction/stability/abs development for many other vehicles when I worked for TRW, in a past life...)
I’ve used the Procal for many years, but it was stolen and, once I replaced it, I reset the tire size. Perhaps I didn’t set the pins properly this time around; I’ll double-check tomorrow.
 

Kmrtnsn

Explorer
You are indeed getting into stability control. Centering the steering wheel may help, but it should learn zero anyway when you fire it up and begin driving.

By chance have you had a dealer program your Jeep with the actual tire size you are running? If you're running larger than stock tires, there will be a discrepancy between the speed you are going, and the speed that stability control thinks you are going. When you turn, stability control monitors a yaw rate sensor and compares that to what it calculates that the yaw rate should be based on steering angle and speed. With a higher than indicated speed due to larger tires, stability control can start to believe that you are starting to spin out due to the calculated yaw rate being lower than the sensor is reading. This would cause it to cut power, and activate and drag the brakes on the outside of the turn.

If the tire size is correct, it is also a possibility that there's just a perfect combination of things where the sensors are fooled into zeroing when they shouldn't, and that particular curve gets just a little past the threshold for activation.

I would wager it'll go away if you get the correct tire size in there though. That's a big one. AEV Procal can do this for you, as can many aftermarket programmers. If you're friends with the dealership, they can do it too. You need the computer to share the correct tire size with the ABS unit that runs stability/traction control.

(I didn't do your JK, but I did traction/stability/abs development for many other vehicles when I worked for TRW, in a past life...)
The Jeep JKU ECS system pulls its “turn” status from the position of the steering wheel clockspring. If the steering wheel is not centered correctly the ECS misreads this information. If the steering wheel is outside of position too far several dash lights are triggered.
 

ventura911

Adventurer
Yep, still doesn’t like going over Grimes Cyn. No codes thrown for the clock spring.

I’d definitely like another opinion, but I’m working nights and only available tomorrow afternoon/evening this week. Maybe next Monday or Tuesday afternoon or evening?
 

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Kmrtnsn

Explorer
Yep, still doesn’t like going over Grimes Cyn. No codes thrown for the clock spring.

I’d definitely like another opinion, but I’m working nights and only available tomorrow afternoon/evening this week. Maybe next Monday or Tuesday afternoon or evening?
I’ll be around. Hit me up and let’s take a look at it. I’m close by, we’ll get you squared away, okay?
 

ventura911

Adventurer
You have one of the absolute best in Simi. Go talk to Tony Pelegrino at Genright.
Yeah, I went by there a few weeks ago and one of his employees said they aren’t doing general work anymore; apparently they had a couple of $250K+builds they were working on.
 

Kmrtnsn

Explorer
Yeah, I went by there a few weeks ago and one of his employees said they aren’t doing general work anymore; apparently they had a couple of $250K+builds they were working on.
Blackstone Jeep Shop in Santa Clarita is awesome for axle and suspension work. They did my air lockers.
 

ventura911

Adventurer
Update: Today I swapped wheels and tires with a friend for a test run through the canyon. The tires were 255/70R18 Bridgestone Dueler A/Ts, vs. my 35x12.50R17 BFG KO2s. The borrowed tires were run at 35 psi (I’ve run my KO2s at 35, 45, and 50, with the 35s too soft and the others good) and in two runs through the canyon, the Duelers resulted in only one activation of the traction control, and that happened when I intentionally pushed it a bit. Otherwise, I was able to exceed 25 mph without pissing off the sensors and computer.

So, based on this non-scientific test, it appears the problem might lie with my tires. This seems strange to me, though, as my first set of KO2s did not cause this problem and these are less than 6 months old.

Anyone have any thoughts?
 
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Kmrtnsn

Explorer
Update: Today I swapped wheels and tires with a friend for a test run through the canyon. The tires were 255/70R18 Bridgestone Dueler A/Ts, vs. my 35x12.50R17 BFG KO2s. The borrowed tires were run at 35 psi (I’ve run my KO2s at 35, 45, and 50, with the 35s too soft and the others good) and in two runs through the canyon, the Duelers resulted in only one activation of the traction control, and that happened when I intentionally pushed it a bit.

So, based on this non-scientific test, it appears the problem might lie with my tires. This seems strange to me, though, as my first set of KO2s did not cause this problem and these are less than 6 months old.

Anyone have any thoughts?
When you and I drove it I don’t think we talked about tires at all. Are the KO‘s load range C? I have E’s on mine but then I’ve dropped back down to a 33” tire too. I’m running 36 PSI and have the TIPM set to activate at 20. You should swing by and drive mine for a comparison. Glad you’ve figured it out after all the head scratching!!
 
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