Standard Cruise Control

[Heimkehr]

I have a 2018 JLU 2.0T with automatic transmission. I have noticed lately while on cruise control let’s say 30mph, when I get on a downhills my rpm’s will shoot all the way from 1600 to 4500 and will engine brake hard.

It just started doing that a few weeks ago.

Per p. 170 of the Owner's Manual:

Using Cruise Control On Hills
The transmission may downshift on hills to
maintain the vehicle set speed.

NOTE:
The Cruise Control system maintains speed up
and down hills. A slight speed change on
moderate hills is normal.
On steep hills, a greater speed loss or gain may
occur so it may be preferable to drive without
Cruise Control

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This is worth an exam by the dealer.

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[RE76]

Have you gotten larger tires?

That’d alter the engine’s RPMs and the transmission’s shift points.

No I have not. I’ve been running the 33 for about two years.

 

[RE76]

Per p. 170 of the Owner's Manual:

Using Cruise Control On Hills
The transmission may downshift on hills to
maintain the vehicle set speed.

NOTE:
The Cruise Control system maintains speed up
and down hills. A slight speed change on
moderate hills is normal.
On steep hills, a greater speed loss or gain may
occur so it may be preferable to drive without
Cruise Control

-----------

This is worth an exam by the dealer.

I’m looking forward hear what the dealership has to say, they seem to be wondering just like me.

 

[RE76]

well finally dropped my JL at the dealership. Like usual they said there wasn’t not much to be done without a check engine light but they would look at it. Tech found codes relating to the abs module. It turns out the traction control, abs system and speed sensors are linked through the same module. The service tech explained to me the Jeep in cruise control operates with hill assist, and one of the abs sensors is went out causing the hill assist to go bonkers. While going 30 mph with cruise control on a steep downhill road the traction control which is in the same module believes one of my wheels is slipping and tries to send power from the opposite wheel to compensate and since there is really no traction issue but the computer doesn’t know that, it makes the RPMs go up to 4500 rpm’s. They are replacing the bad sensor and they assured me that will fix the issue. I’ll post later if it really helped with my problem. Jeeps now on day are way to smart for their own good.

 

[RE76]

Here are a couple of videos showing the rpm’s going haywire while in cruise control 30mph. Tried to attach before but the server wouldn’t allow me.

 

[KevinC11]

1. Why are you using cruise control at 30mph? Seems at that slow of a speed you would be constantly varying your speed throughout. Most CC won't even engage until 35mph.

2. Why don't you have the transmission gear showing on your dash? That would give you a better idea if the transmission is downshifting lower than it needs to for engine braking.

Just me random thoughts...

KevinC

 

[Hogdreamer]

1. Why are you using cruise control at 30mph? Seems at that slow of a speed you would be constantly varying your speed throughout. Most CC won't even engage until 35mph.

2. Why don't you have the transmission gear showing on your dash? That would give you a better idea if the transmission is downshifting lower than it needs to for engine braking.

Just me random thoughts...

KevinC

You can use the Wrangler CC less than 35 mph.
When engaged, the Cruise Control takes over accelerator operations at speeds greater than 20 mph (32 km/h) per the owner's manual.

I have my transmission gear showing but sometimes I wish I didn't. It's frustrating how often the gear shown is less than I would expect with the V-6. Especially wish it would stay in 8th more often on the freeway to help my mileage.

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