2004 Unlimited Cruise Control

[cjkirchman]

I haven't posted here in a while but I just got an automated email from the forum today. It was lamenting over how much it missed me. So I figured I would drop by with a question.

I have an issue that has been bugging me ever since I bought a 2004 Wrangler Unlimited back in March of last year. It has the four speed automatic transmission and I live in the mountains of Western North Carolina. When I am driving on the highway I use the cruise control. Why is it that whenever I start to go up a hill with the cruise on, it stays in overdrive as long as possible until it panics and shifts all the way down to second gear at 60 miles per hour? The RPMs shoot up to like 4500 for three seconds of what sounds like brutal torturous acceleration and then it goes back into overdrive. Why doesn't it shift down into third gear in order to maintain speed up the hill? If I want it to do that, I have to manually disable the overdrive by pushing the button when I start up the hill and then push the button again to turn it back on once I get to the top.

Is there some kind of problem with the cruise control? I have searched all over the Internet for another mention of this issue but I haven't been able to find one. Maybe I'm the only man who isn't afraid of seeming like a pansy for complaining about the cruise control in his Jeep. :lol:

But seriously if anyone has experienced this before or could offer any suggestions for a solution then you would help me fix the only thing I don't love about my Jeep. Plus you would have my eternal gratitude. And really what more could you ask for?

 

[jps4jeep]

I'd take it to a dealership if it really bothers you. could be issue with the cruise control Modual

If it were me, If I was anticipating a hill, I would just stab the gas to get it into third at the bottom of the hill and then let the cruise take over on the incline.

 

[cjkirchman]

I've done that before too, but I figured it used more gas than just pushing the "O/D Off" button. And if there is one thing I don't need to use more of, it is gas!

 

[SteelHeadz]

OPERATION
When speed control is selected by depressing the ON switch, the PCM allows a set speed to be stored in PCM RAM for speed control. To store a set speed, depress the SET switch while the vehicle is moving at a speed between 35 and 85 mph. In order for the speed control to engage, the brakes cannot be applied, nor can the gear selector be indicating the transmission is in Park or Neutral.

The speed control can be disengaged manually by:
Stepping on the brake pedal
Depressing the OFF switch
Depressing the CANCEL switch.
Depressing the clutch pedal (if equipped).
NOTE: Depressing the OFF switch or turning off the ignition switch will erase the set speed stored in the PCM.

For added safety, the speed control system is programmed to disengage for any of the following conditions:

An indication of Park or Neutral
A rapid increase rpm (indicates that the clutch has been disengaged)
Excessive engine rpm (indicates that the transmission may be in a low gear)
The speed signal increases at a rate of 10 mph per second (indicates that the coefficient of friction between the road surface and tires is extremely low)
The speed signal decreases at a rate of 10 mph per second (indicates that the vehicle may have decelerated at an extremely high rate)
Once the speed control has been disengaged, depressing the RES/ACCEL switch (when speed is greater than 30 mph) restores the vehicle to the target speed that was stored in the PCM.

While the speed control is engaged, the driver can increase the vehicle speed by depressing the RES/ACCEL switch. The new target speed is stored in the PCM when the RES/ACCEL is released. The PCM also has a "tap-up" feature in which vehicle speed increases at a rate of approximately 2 mph for each momentary switch activation of the RES/ACCEL switch.

A “tap down” feature is used to decelerate without disengaging the speed control system. To decelerate from an existing recorded target speed, momentarily depress the COAST switch. For each switch activation, speed will be lowered approximately 1 mph.

OVERSHOOT/UNDERSHOOT
If the vehicle operator repeatedly presses and releases the SET button with their foot off of the accelerator (referred to as a “lift foot set”), the vehicle may accelerate and exceed the desired set speed by up to 5 mph (8 km/h). It may also decelerate to less than the desired set speed, before finally achieving the desired set speed.

The Speed Control System has an adaptive strategy that compensates for vehicle-to-vehicle variations in speed control cable lengths. When the speed control is set with the vehicle operators foot off of the accelerator pedal, the speed control thinks there is excessive speed control cable slack and adapts accordingly. If the “lift foot sets” are continually used, a speed control overshoot/undershoot condition will develop.

To “unlearn” the overshoot/undershoot condition, the vehicle operator has to press and release the set button while maintaining the desired set speed using the accelerator pedal (not decelerating or accelerating), and then turning the cruise control switch to the OFF position (or press the CANCEL button if equipped) after waiting 10 seconds. This procedure must be performed approximately 10–15 times to completely unlearn the overshoot/undershoot condition.

 

[cjkirchman]

Thanks for the information Mikey.

Am I correct in thinking that, in your opinion, the problem I described is due to a learned "undershoot/overshoot" condition in the cruise control module?

That's the best suggestion (actually, the only suggestion) I have received as a possible solution to this issue so far. Although I don't ever recall setting the cruise without my foot on the accelerator pedal. But it may be that I am doing it without realizing it.

I am still not sure how that explains the shifting from OD to 2nd issue but I will give it a try and see if it improves anything.

Thank you again for taking the time to post that info.

 

[SteelHeadz]

I've exausted my resources on this issue your having. i have not found any issues, or any relevant case. so at this point, try to perform that procedure on the Overshoot/ Undershoot condition. I'll keep looking for any possible causes or answers.