Hill Descent Control - Speed Doesn't Change

[Rover11]

2021 JLU, Rubicon, 3.6L
When I engage the Hill Descent Control (HDC) , using the exact rules/process explained in the manual, the button light comes on, the dash and off-road pages indicate HDC is activated, but as I move down the hill, using the manual shift to change the speed setting I can never get the speed to increase beyond the starting speed of 0.6mph (should increase +0.6mph with each gear shift move to +). All criteria are met:

• In 4L
• Speed is below 5mph (*)
• Facing downhill on a hill of serious slope
• Parking brake off
• Doors closed

Has anyone else experienced this? Any ideas of why the speed change feature does not work?

(*) When manual says speed must be below 5mph, does that imply I should be moving when the button is pushed (its the one thing I have not tried yet)?

For those of you that have changed features via programming, is it possible to affect HDC by changing a SW setting (I had the dealer update SW to account for changing tires to 35's and wonder if they accidentally turned off the HDC in that process)?

I realize that HDC-like behavior can be achieved simply by managing the transmission gear manually in 4L (and I actually like this approach better), but its really messing with my head that this does not seem to work, and I'd like to fix it.

Thanks!

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[avensis]

On your Jeep Wrangler Unlimited Rubicon, the "less than 8 km/h" setting means the vehicle must be moving (even very slowly) when HDC activates.
If the speed remains stuck at 0.6 mph, the most likely cause with 35" tires is incorrect tire diameter/ABS recalibration after the update.

Mini Militia App Lock​

 

[3TV]

Are you in Offroad+ mode? I've used mine a couple of times and it seemed to work just fine, but I've always been in Offroad+ mode when I use it. I don't know if that is needed or not, just asking.

I have 39" tires on mine, with speedometer calibration using a Tazer and one of those roadside radar signs that always say "Slow Down" when you pass them. But the MPH displayed on my dash display matches what the radar sign says.

 

[jeepoch]

When using mine, moving or stopped, it automatically selects the slowest 0.6 mph speed. It stays there until I use the shift lever to mimick changing a gear in AutoStick (M). Once enabled I can speed up or slow down based upon how many times I bump the shift level either up or down. It incrementally adds or subtracts 0.6 (or 0.7) mph each bump until either the upper limit of 5.0 or the lower limit of 0.6 mph is achieved.

Works great. I swear by it. Use it all the time here in the mountain wilderness of Colorado. Kind of strange keeping your foot from pressing down on the brake pedel on the steepest of descents. You know it's working by going a steady constant speed and listening to the ABS braking system modulate the braking forces applied to each brake.

To disable, toggle the HDC button off, and I momentarily put the 8-Speed back into (D)rive. Once I see the tranny select a gear, I then go back into AutoStick (M) and manually select whatever gear is most appropriate for the terrain. Very seldom do I ever find myself not in 'manual' mode while off-road, especially out here in the high mountain wilderness.

I love my JL. Best investment in a daily driver I've ever made. The entire state of CO has become my back yard. Sorry your having issues. I wouldn't leave home on any high-altitude trip without it. I'm now spoiled rotten. Hill Descent Control really is that cool.

Jay

 

[Rover11]

On your Jeep Wrangler Unlimited Rubicon, the "less than 8 km/h" setting means the vehicle must be moving (even very slowly) when HDC activates.
If the speed remains stuck at 0.6 mph, the most likely cause with 35" tires is incorrect tire diameter/ABS recalibration after the update.

Mini Militia App Lock​

Thank you so much for checking in on this! After I wrote the post, I went out and tested engaging HDC while moving (along with all the other conditions being met), and it still didn't work...:-(....I will have the dealer that reset the wheel size via programming for my 35in tires check to be sure they didn't make a mistake. The actual tire diameter is 34.36, (315/70/17), but they programmed for 34.5...I don't think that matters, but just posting the info as accurately as possible. On my "35's", going down the freeway, the speed and mileage all seems to match, but I will check that too this weekend.... Thanks again!

 

[Rover11]

When using mine, moving or stopped, it automatically selects the slowest 0.6 mph speed. It stays there until I use the shift lever to mimick changing a gear in AutoStick (M). Once enabled I can speed up or slow down based upon how many times I bump the shift level either up or down. It incrementally adds or subtracts 0.6 (or 0.7) mph each bump until either the upper limit of 5.0 or the lower limit of 0.6 mph is achieved.

Works great. I swear by it. Use it all the time here in the mountain wilderness of Colorado. Kind of strange keeping your foot from pressing down on the brake pedel on the steepest of descents. You know it's working by going a steady constant speed and listening to the ABS braking system modulate the braking forces applied to each brake.

To disable, toggle the HDC button off, and I momentarily put the 8-Speed back into (D)rive. Once I see the tranny select a gear, I then go back into AutoStick (M) and manually select whatever gear is most appropriate for the terrain. Very seldom do I ever find myself not in 'manual' mode while off-road, especially out here in the high mountain wilderness.

I love my JL. Best investment in a daily driver I've ever made. The entire state of CO has become my back yard. Sorry your having issues. I wouldn't leave home on any high-altitude trip without it. I'm now spoiled rotten. Hill Descent Control really is that cool.

Jay

Thanks for checking in on this! Really cool that you love it so much and I appreciate your sharing that! For me, while figuring out the source of my problem is frustrating the good news is that in 4WL, using the manual stick, I can pretty much simulate the same behavior as HDC.....Bad news, is that this is really bugging me due to wondering the source to be sure it is not an indicator that something else is wrong. As you can tell, I am a bit of a perfectionist.....
Anyway, I plan to make a lot of trips to California Sierras with this vehicle (as I did with my WJ for years) and love the increased freedom the Rubicon gives me to go so many more places! Thanks again!

 

[Rover11]

Are you in Offroad+ mode? I've used mine a couple of times and it seemed to work just fine, but I've always been in Offroad+ mode when I use it. I don't know if that is needed or not, just asking.

I have 39" tires on mine, with speedometer calibration using a Tazer and one of those roadside radar signs that always say "Slow Down" when you pass them. But the MPH displayed on my dash display matches what the radar sign says.

Thank you so much for checking in on this! Very informative that you have 39's and its not a problem. I did NOT think to check in combination with the OffRoad+ mode and will do that this weekend! May I ask, are you happy with the Tazer? I have been considering getting that for some other reasons. I first saw the Tazer product when I was first looking into adding AUX switches....but...was wondering from your viewpoint how complicated it is to use, and whether there is a risk of messing up in a way that creates "irreversible damage", requiring a visit to a dealer. As I am sure you know the dealer programming price is ridiculously expensive! Any thoughts on the risk of using the Tazer programing and accidentally making a bad mistake? Thanks again!

 

[Ratbert]

Thanks for checking in on this! Really cool that you love it so much and I appreciate your sharing that! For me, while figuring out the source of my problem is frustrating the good news is that in 4WL, using the manual stick, I can pretty much simulate the same behavior as HDC.....Bad news, is that this is really bugging me due to wondering the source to be sure it is not an indicator that something else is wrong. As you can tell, I am a bit of a perfectionist.....
Anyway, I plan to make a lot of trips to California Sierras with this vehicle (as I did with my WJ for years) and love the increased freedom the Rubicon gives me to go so many more places! Thanks again!

Sorry, but 4lo + manually shifting isn't close to hill decent or hill climb. There's a reason there's a dedicated button for it.

 

[Rover11]

Okay.....interesting....appreciate the honesty and thanks for the feedback....further motivation to find the problem!

 

[Alan_Hepburn]

Sorry, but 4lo + manually shifting isn't close to hill decent or hill climb. There's a reason there's a dedicated button for it.

Right - the "duck button" actually activates and controls both the throttle and the ABS system to regulate speed. That's why it makes so much noise when it's working.

 

[Rover11]

Thanks again everyone for the feedback. Unfortunately, yesterday, I tried everything suggested here and a few other things, but HDC is still not working correctly. When I engage it, It just stays at 0.6mph no matter what I do with the stick shift. When I turn the button on and off, I feel it engage and disengage....so I know it is trying to do its thing, but it just won't change speeds. I'm going to check the ABS sensors (I understand they detect wheel speed and the HDC system feeds off of this) and the pedal brake switch (apparently HDC uses feedback from that). I've also seen comments that maybe the battery voltage is a hair low and might affect this (.......). Overall, very odd!!

 

[3TV]

Thank you so much for checking in on this! Very informative that you have 39's and its not a problem. I did NOT think to check in combination with the OffRoad+ mode and will do that this weekend! May I ask, are you happy with the Tazer? I have been considering getting that for some other reasons. I first saw the Tazer product when I was first looking into adding AUX switches....but...was wondering from your viewpoint how complicated it is to use, and whether there is a risk of messing up in a way that creates "irreversible damage", requiring a visit to a dealer. As I am sure you know the dealer programming price is ridiculously expensive! Any thoughts on the risk of using the Tazer programing and accidentally making a bad mistake? Thanks again!

I've been happy with using a Tazer. I've used them in two different Jeeps, a 2022, and 2025. I haven't done anything fancy with them, just resetting the tire size and axle gear ratio, disabling automatic Start/Stop, and changing to LED turn signal lights. There is a learning curve to figure out how to use a Tazer, but everything has worked as it is supposed to with no problems from the Jeep because of the Tazer.

 

[Rover11]

I've been happy with using a Tazer. I've used them in two different Jeeps, a 2022, and 2025. I haven't done anything fancy with them, just resetting the tire size and axle gear ratio, disabling automatic Start/Stop, and changing to LED turn signal lights. There is a learning curve to figure out how to use a Tazer, but everything has worked as it is supposed to with no problems from the Jeep because of the Tazer.

THank you! Appreciate the input and perspsective!

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