Cruise Control Gone Bad

[tvdan1043]

My 2005 Wrangler X has a cruise control issue. Everything on the left-hand switch works fine (On/Off, Set). But the right-hand switch has some problems.

Until recently, Cancel was the same as tapping the brake pedal. The cruise control disengaged but remained powered on. Now, Cancel functions the same as Power Off, wiping the speed memory and making the Resume function useless.

Accelerate sometimes does not hold the speed after I release the Accelerate button. If I accelerate from 55 to 65, then release the Accelerate button, about 1 time out of 10 the cruise control will return to 55. Similarly, Coast also sometimes does not hold the speed, so if I coast from 65 to 55, about 1 time out of 10 the cruise control will return to 65 after I release the Coast button.

Any ideas?

 

[SteelHeadz]

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. I hope this info. helps.

 

[tvdan1043]

Ok, the overshoot/undershoot info is interesting although it doesn't really apply to my coast/accelerate problem. It also doesn't answer the Cancel part of my question.

 

[tvdan1043]

Can anyone answer my original question? I really need to get this fixed. Thanks.

 

[SteelHeadz]

Hard to tell , you would need to check and verify the connections on the switches, servo and brake pedal switch. If all checks out okay, I would guess that the cruise control switch is bad. The switches are a Mux controlled circuit, meaning, multiple functions with several different resistance value to be interpreted by the PCM that uses only 2 to 3 wires with 5 functions.

 

[abe]

iratenannerk im not being a D but ....... sure its not a toyota

 

[tvdan1043]

Thanks SteelHeadz, I'll check that out.

 

[tvdan1043]

UPDATE: I ordered a new switch for the right-hand side of the steering wheel (Resume/Accelerate, Cancel, Coast) and installed it today. Fixed my problem. So it was the Cancel switch all along, making the system think it was the Power switch.