labbayk

Hi guys - big fan of the forum. Spend a lot of time learning and researching. I'm having an issue that I just can't pinpoint. I'm waiting to get paid on Friday to take her into a local shop for help. Wanted to diagnose this myself first though so I can understand how my JK works. I do basically all the work on it. Hoping for some advice. TIA!

A couple of weeks ago, I changed out 2 ABS sensors because I got the MIL and ABS lights and the Jeep was driving erratically. This week I still had ABS lights on but now the Jeep goes into limp mode after the Brake Warning light appears and this all kicks in at 10 mph driving a straight line or turning. Sometimes I can reset by pulling over and cycling my shifter. Other times the Brake Warning light appears on the freeway and I can hold my speed with higher revs. I used an ABS equipped reader and changed the front right and left rear. The codes at this time were "circuit" codes. After changing them, the lights wouldn't turn off but she wasn't in limp mode anymore and I could shift (I have an auto 3.6). I pulled the codes again and then got the abs code containing "comparative performance". So I changed the harness that the sensor plugs into in the front. The pins in the harness were green and super corroded. The rear, I inspected the tone ring and cleaned the sensor. No improvement.

I undid all 4 of my sensors, I cleaned them with QD spray, I used dielectric grease on the plugs, I spun the hub and tried to inspect the tone wheel for debris, I followed the harnesses throughout the under side of the jeep to check for tears or crimps, and I read the wires with a multi meter to make sure power was going through.

Despite all of this I was doing my front passenger brake pads. I inspected the front sensor and it was covered in a rust colored grease. The grease was layered on the sensor. I sprayed BPCleaner in the opening in the hub, and a rust/maroon colored ickiness dripped out of the hub. So now I am thinking the tone ring is contaminated in the front but no tone codes are pulling for this.

Fast forward a few days. I changed out the caliper on the front driver side because suddenly the caliper started sticking. Inspected and cleaned the ABS sensor on this side, no dirt in the harness or on the sensor. I bled my brakes and topped off the res. Now the sensor on this side is triggering a "comparative performance" fault.

The only thing I can think of is that I need new bearings in the front because the tone rings can't be cleaned as it is an assembled non serviceable hub. Or I might need a new ABS module. I am leaning towards the hubs though because the codes and performance are erratic. If it was the module, wouldn't the codes be more consistent?

Someone posted on here a while ago that bad abs sensors do not cause transmission weirdness. He was able to drive and shift fine (MILs on of course). Until I changed the rear sensor, jeep was in limp mode. What I can't figure out really is why am I going into limp mode over ABS? Guess it's time to put miles on the new Harley this week. x.x

12 jku 3.6 with lift and bigger tires @ 100k miles.

labbayk

For anyone who is surfing now or in the future who this might help -- issues are fixed. It took A LOT of research and troubleshooting but it's done.

1. The claim that faulty/bad/broken/not working ABS sensors/harnesses "do not" disable the transmission or cause other systems to malfunction was not verified by me. I found that after redoing specifically my rear wheel speed sensor wiring and sensors, the Jeep was out of limp mode. I'm not sure why but that was my case. Tested a few times. I highly recommend dielectric grease and QD cleaner if you offroad, do creek crossings, play in the mud, etc.

2. So, I have a 2012 3.6 with no tipm or pcm modifications. If you do too and you are in limp mode with abs issues, then inspect all of your sensors. Get an ABS code reader and pinpoint which ones are bad. Some clues....if your code has "circuit" in it, then it's a bad sensor or harness. If your code has "implausible" in it, it could be your hub or your sensor or your harness. If your code has "comparable" in it, it could be your sensor or your hub/tone ring. Because my rear sensor/harness was the culprit to bogging the JK down and kicking on the brakes randomly, this triggered a fault in my front left sensor. The FL sensor was indeed okay after fixing the rear left. Must have been the whole Jeep's behavior tripping faults everywhere. So my advice is to start in the back. Based on my experience, chances are if you are in limp mode because of ABS, one of your rear's are bad.

3. I replicated quite a few times, that when a rear speed sensor and harness go bad or are not set up right, then my BRAKE Warning light appears and I go into limp mode. So after I changed the sensor, I bought a new harness from the dealer. I couldn't see anything wrong with my current wires and I tested them for continuity and they tested good. So I went out on a limb and chopped off the plugs and spliced in the new ones. This solved my limp mode and brake light problems. Now, I still had abs and traction control lights but she is moving again so yay!

4. In my OP I questioned my brakes because I had just done them and that's when the light and limp mode began. Maybe it was just weird timing. The ABS system is synced with the Brake module in our rigs. But in my case, they had nothing to do with my ABS faults. Gone through several rotors and pads and I have never seen that BRAKE light on before. I checked and rechecked hoses and the calipers and pads for rubbing, corrosion, leaks, and looseness. Bled the lines, checked the MC. Checked hard lines. I did find that my hub assembly on the passenger side was busted and the rust colored brake parts cleaner run off that I saw was the bearing grease and metal shavings from a failed bearing inside. So I picked up a new front hub assembly that has it's own WSS. Installed, and now all of my lights are off of the dash and no more WSS codes. So this means that the front speed sensor and harness could not read my wheel speed from my tone ring in the hub because of crud jammed in there from failure.

FWIW -- I wheel frequently and she is my daily driver. I have gone through several front wheel bearings because of the stress on them. Mud, salt, and sand destroy these components. Flexing stretches these sensors and their harnesses out. First time in 100k miles that I've ever had this happen but now I keep spare sensors and plugs in my tools. I am really lucky she decided to bog down after I drove home from a wheeling trip in Harlan Kentucky!!

Hope this helps! Good luck!

Cingham3

resharp001

OP hasn't posted in almost 3 years, so likely not around. Tried to look at your thread on the other forum, but the link is to general topics page. Maybe start a new thread over here on this forum and see if we can help.

Cingham3

Hunny Cortez

After changing position sensors an a alignment i thought back to my Nissan an whenever i needed brakes it would throw the ABS an TCS soo once i topped off the brake fluid it would stop but it never went into limp mode soo thinking it was something more serious in my jeep jk i fixed whatever codes it was throwing an still freaking throwing ABS TCS an limp mode grrr so i popped the hood again this time i shined a flash light on brake fluid box an sure enough it was under max i topped it off an now no ABS OR TCS SMFH!! before you guys take it to repair just take a look it may just be low brake fluid