JKU VSS and TCS issue

HAFICON

Adventurer
#1
Seeking advice:

2012 JKU 94k miles, random at start up the VSS & TCS light come on and they on, these are accompanied by the down hill assist flashing. This happens after the engine is started. Shut the engine off remove the key and open the door so everything turns off. Re-Insert let Jeep go through all chimes, lights go off and start the engine. BAM all good no warning lights.

Now at times while driving on smooth, straight roads average 40-50mph you can feel the Jeep auto breaking, starting to engage VSS, at times the VSS light will start flashing and the Jeep breaks as designed by the VSS system. Sometimes the VSS light doesn’t not light up, but you get the auto breaking action.

Any ideas before I have the dealer plug into it? The dealer close by is Jeep friendly, does full mods and have an Off-Road course on their lot so they are not going to give me the normal crap a dealer would.

Thanks
James Blue
 
#2
How is your battery? Sometimes a low battery can cause problems. Do your front tires have a lot less tread than the rear? I've had that activate my stability control before.
 

HAFICON

Adventurer
#3
How is your battery? Sometimes a low battery can cause problems. Do your front tires have a lot less tread than the rear? I've had that activate my stability control before.

Tires are all good, bought all new they have 20k on them maybe. Going to check connections at battery. I will load twat the batteries I think they are fine but will see.
 
#4
My JKU is a manual. However I've had the same issue. Tracked it down to the front wheel speed sensors. Since my lift, and 285's, the tire would rub ever so slightly on the wheel speed sensor wire (both sides). Failure mode was intermittent at first. Lights would light up. Driving straight for a while would cure it. Sometimes a key cycle would cure it.

Ultimately, new sensors and wires. At least in my case.
 

HAFICON

Adventurer
#5
My JKU is a manual. However I've had the same issue. Tracked it down to the front wheel speed sensors. Since my lift, and 285's, the tire would rub ever so slightly on the wheel speed sensor wire (both sides). Failure mode was intermittent at first. Lights would light up. Driving straight for a while would cure it. Sometimes a key cycle would cure it.

Ultimately, new sensors and wires. At least in my case.

Ok thanks I will check that, I replaced all the sensors a long time ago troubleshooting something else. I’m not a parts changer, but in this case 4 sensors was cheaper than dealer testing. Turns out it was a broken wire for the speed sensor. I kept all the sensors I removed I will check that out this weekend. On a 2nd note thanks for the input I forgot all about the broken wire I fixed I need to check it. I soldered in new wire coated it in anti seize and heat shank it but I was getting similar issues then.
 

HAFICON

Adventurer
#6
So as I mentioned the tires are all good, cable ends are all set. Dual battery set up is 3-4 years old but batteries are fine, even when paralled the issue still occurs but is random. May go a few days with out seeing it then it pops up. So the search continues, as suggested I am checking all whee speed sensors. I know the rear ones have a tendency of getting really dirty as they are semi open to the elements.
 

Mass_Mopar

I should post more often
#8
For me it was a wheel speed sensor harness that had worn its insulation off and would ground out only when driving in the rain. The Jeep would chime and pull fuel from the engine but no warning lights. Felt like it was chewing through bad gas but if I shut traction control off it would be fine.
Also had a loose battery terminal intermittently light the dash up like a Christmas tree while driving...
 
#10
For me it was a wheel speed sensor harness that had worn its insulation off and would ground out only when driving in the rain. The Jeep would chime and pull fuel from the engine but no warning lights. Felt like it was chewing through bad gas but if I shut traction control off it would be fine.
Also had a loose battery terminal intermittently light the dash up like a Christmas tree while driving...

Sounds good going tominspect them closely.. Jeep was towed on a car carrier it is possible something got damaged
 
#12
I've had to replace the same rear wheel speed sensor twice for this problem over about a 30k stretch and had my lights come on briefly last week so it might be time for another one. Went to Autozone because my scanner doesn't show ABS codes to see exactly which was causing the issue.

Also if a speed sensor goes out the cruise control won't work.
 
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