I have read and re-read countless threads on the subject but have found no difinitive "here's how to fix it" answer. My ABS Inop light has been on since I bought the car. My cruise works and my 3rd brake light bulbs are all good and not LED. I had it scanned for codes and the dealer said it was an open circuit. I have replaced both front speed sensors. I know we say the wiring harness is prone to failure. Where is the failure? Anyone actually found where the failure occurs? I have also read that if the cruise still works and the ABS Inop light is on, it is the front system but if the light is on and the cruise also does not work, it is the rear sensor. Just trying to narrow it down so I can troubleshoot effectively and not just throw parts at it until it is fixed. I have inspected what I can see of the harness wiring to the front sensors and they appear to be in good condition, but I can only see so much of them before they go up into the engine bay somewhere out of sight. On a side note, recently my "Brake" light has come on and stays on. It used to come on randomly at times, but go off. I have checked the e-brake switch and it is making/breaking contact as it should. The fluid level is fine and the brakes operate fine, no change in pedal pressure or anything. I see that an imbalance between the front and rear circuit pressures can set that light on. Just looking for input from others who have had similar issues and were able to successfully repair the issues without yanking the bulb out of the cluster. I know the ABS Inop light is a common issue so there has to be a common fix for it.

 

I know this wont really help you, but mine was doing what yours is doing. I noticed the ABS light would come on after a few miles of driving. Shut the car down light would be off... drive it, no light...then next time I would see the ABS light come on again...

I also noticed when backing out of the driveway then going forward, the lights would never come on....crazy!! If I didnt back up first, the light would come on.... Then it stopped alltogether.... I have no clue why..... In the last couple of months, no issues.

 

The Brake light needs sorted out ASAP, You need to know why that is on. The reason they have the pressure sensor is because a master cylinder can fail internally and not have any external leaks. Here are a couple of quick tests. Find a dark place and turn your key on. Pull up your park brake. Does the light get brighter? If it gets slightly brighter then it is not a park brake issue. If there is no change in the light when you pull the park brake then the park brake is most likey the reason the light is on.

To see if the car is safe to drive go out someplace with few cars and get the car up to about 50 MPH. Now let go of the wheel and pump the brakes getting a little harder each time. Once you hit 30ish slam them one. Does the car pull left, right or does it stay straight? If the car stays straight you are looking at an electrical issue or a problem with the sending unit.

ABS
There is no single common issue with your ABS system. Without a scanner it is very hard to fix these systems. Do you know if the car still has the open? If you paid to have the car fixed at the dealer why not take it back and say it is not fixed? Common issued include bad wiring harness and bad wheel sensors and even bad Wheel bearings making it look like it is a bad wheel sensor. There is a lot of less common issues that can happen at the main ABS system also.

If the car has been driven a long time with the ABS light on there could be multible layers issues. I have had cars with a harness issue that would not report anything from the wheel. Fixed that, got the light out only to have it come back on during the test drive. I got the harness to report to the ABS system now I find out the wheel sensor has an intermittent issue in it and it will set a code after hitting a couple of bumps. This really pisses the customer off because they end up getting two phone calls both wanting more money.

 

Thanks all. I just had the dealer scan for codes before I got a scanner that worked. They said the code was for an open circuit. Did not have them try and fix the ABS Inop issue. I replaced both front wheel hub assy's, including the speed sensors and bearings a month or so ago hoping that would fix it. It's the "bad harness" I'm trying to pinpoint. Which harness are we referring to? I have looked all over shoebox's site but can't find much info on this particular issue.

I will check the brake light tonight. It used to go on and off with the e-brake, but sometimes it would stay on. Now it just stays on all the time. E-brake on or off. I will also test the brakes as you mentioned. I was hoping since there are lots of people who have the ABS light problem, someone had narrowed it down as to where exactly to look for the faulty wiring.

 

Mine was doing the same thing and then I figured out it was the easiest fix I had ever done. If you look below at the image, there are two wires grounded with one bolt, make sure the wire (i believe its the top one), the one that goes back towards the passenger side mirror, is clean and grounded properly. Mine was covered in paint and was not grounding properly so i used a rotary grinding wheel to grind the paint and excess junk off the two wires contacts, the bolt itself and the area on the shock tower and my problem has never come back. I had to fidgit with the wire too and move it to a certain position so that way the lights would stay off. This may do the trick!

 

I have looked at too many cars in the last few years. I think on the Camaro the wheel harness is replaceable. There is a connector at the harness inside the engine compartment and one at the sensor. Because the wheel is constanlt turning and this harness is exposed to road hazards it is the most common spot for harness damage.

Also Checking for bad ground is always a good idea.

 

The brake light does get brighter with the e-brake on. No issues when doing the stopping test. Gotta dig into it more. Here is something I'm sure is out of the ordinary. It is basically just wet, not dripping or anything. I can assume some seal on the backside of the master cylinder is leaking. Would this cause the brake light to come on? You think it's just a master cylinder replacement?

 

That would Fail PA state inspection if the mechanic noticed it. It is a sealed system any signs of leaking or leaking history is a problem.

 

I'm sure it would fail here as well seeing how the brake light is always on. Question is, is that causing the light to stay on. Should I go ahead and replace the master cylinder?

 

I would replace it. It might be causing the light to stay on. If the sensor doesnt sense the right pressure it will kick the light on.