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Old 11-10-2015, 09:52 PM
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Cruise control issue

Sometimes when I set the cruise say at 65mph & after going a few miles or 10 miles the cruise just turns off. It doesn't do it every time but when it does the cruise will not turn back on until I shut the key off & restart the engine. Any help is greatly appreciated.

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Old 11-10-2015, 11:09 PM   #2
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Could be something else but when it happens, see if the blower is only blowing out the defrost vents & won’t switch to the center vents. If that happens it indicates that you are losing engine vacuum in low vacuum situations like accelerating or going up a hill. Even a steady high speed could do it. There is a vacuum reservoir under the battery in the fender well to keep that from happening but if the vacuum hose falls off or cracks & leaks as it is known to do you lose all vacuum reserve. The same vacuum line works the CC & HVAC air flow. Easy to check.

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Old 11-11-2015, 09:46 PM
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Will the vacuum problem cause the green cruise light to go off in the dash? Then after the light goes out it will not turn back on until I shut off the ignition & restart the engine. It has done this while I had the ac on & the fan on high blowing out the vents. The air coming from the vents never changed. I've even killed the engine & restarted as soon as the cruise shuts off at 65mph & it will then turn back on & i can set it at 65mph again.
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Old 11-11-2015, 10:36 PM   #4
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Probably not a vacuum issue if the HVAC is functioning properly. It is somewhat common to lose vacuum either at the intake manifold or reservoir & get the blower defaulting to defrost. That would also affect the CC when equipped so I took a shot.

Could be a faulty switch on the steering wheel, otherwise pretty much everything else in controlled through the PCM & the brake switch. It does sound electrical if the key off & on restarts it. Then you have the servo which depends on the various signals. Can’t help beyond that & don't know how the dash light works other than the PCM sending the signal.
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Old 11-12-2015, 07:45 PM
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Ok thanks a lot!
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Old 11-12-2015, 08:04 PM   #6
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Also tied to park neutral switch

I know when I swapped in as auto PCM the cruse would never set because on the 5 SPd the factory harness has a jumper across the park neutral switch so starter can engage but on an auto pcm it thinks it is not in gear and cruise will never set with that jumper in place

Went back to 5spd PCM and worked agin

I only swapped in the auto xj PCM to make sure all else worked in case I had a future issue I thought might be PCM related so that way if I did a diagnostic swap I knew what I should expect
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Old 11-12-2015, 09:08 PM   #7
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After think about what you describe my guess is a damaged clock spring with intermittent short
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Old 11-12-2015, 09:42 PM   #8
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If everything else works, might it be a faulty brake light switch?
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Old 11-12-2015, 10:46 PM   #9
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If everything else works, might it be a faulty brake light switch?
No.
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Old 11-13-2015, 01:16 AM   #10
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No.
Just curious but why do you say that?
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Old 11-13-2015, 07:02 AM   #11
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The brake light switch is one thing that does not go thru ignition as it works with key off

Plus if bad could easily notice in brake lights not working correctly

Finally not seeing how a restart would reset it in any way

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