ABS Light Diagnosis and Fix

Discussion in 'SN95 4.6L Mustang Tech' started by nittanylion45, Jul 25, 2011.

  1. Hello,

    I just went through the whole diagnosis and fix on my ABS warning light. I thought I would share what I learned.

    My Car: 99 Cobra

    My light was coming on intermitently (at first). Eventually, the light was on all the time. From what I understand, IN GENERAL: If the light comes on when you start the car and stays on, you have a module or wiring problem. If the light comes on after the car is moving >8mph, then the problem is probably a wheel sensor.

    Also, there are very few code scanners that can read the ABS codes. I tried a snap-on $8000 scanner that should have worked... it would not communicate with my module... this is another sign of a bad module. FYI - Ford dealership wanted my car for the whole day just to read the ABS code!!!

    Even though clue #1 was a bad module, I went through the entire diagnosis anyway (hoping for a bad wheel sensor!). I cleaned all my wheel sensors then checked all the wheel sensors and grounds with a volt/ohmeter. For excellent details on how to do this for 98-99 (others???), go to:

    Mustang 1998+ ABS Diag Info

    I don't know who's site this is, but is has everything you need to diagnose the wheel sensors, fuse, power supply, and grounds. It has all the pin diagrams as well. There is even a page for 94-96 mustangs.

    My car passed all wheel sensor tests. Adding up the info..... Module will not communicate with ABS code reader, Light is on and stays on right after start-up, and the POS Bosch ABS modules used in these cars had an inherent weakness in the soldering joints inside the module... I diagnosed my problem as a bad module.

    OK, now I heard the dealership will charge $900-$1000 for the ABS module replacement. I could not find any new aftermarket ABS modules. So, I researched it and found that a nice little business has popped up for repairing these modules. Do a search on ABS Bosch Module Repair... and you will find a few: Module Masters, ect.

    I found a guy (seller Bosch0004) on Ebay who repairs these module for $100. Here is a link to his posting:


    Now, there is a video on YouTube.... you can remove the ABS module WITHOUT breaking into any hydraulic lines. Here is the link:

    ‪How to replace Mustang ABS control module WITHOUT removing lines‬‏ - YouTube

    I drove my car for a week and a half with the module out.... I ziplock bagged the hydraulic unit to keep it dry and I zip tied the module to firm it up. (Drive your car at you own risk!!!).

    I sent my module off to Bosch0004 and he had an incredible 4 day turn around (including shipping both ways!).

    I reinstalled the module.... and... everything is fixed.:hail2:

    I hope this helps those who are having a similar problem.

  2. Yea anything other than the wheel sensors are expensive with ABS. For me, I was lucky enough to just have to buy a new LF wheel sensor.

    Thanks for sharing. The info will be usefull when the time comes.
  3. Wow, talk about timely. My abs light has just started coming on about 5-10 minutes after driving and then would go out about 5 miles later. I'll cetainly use the first link to diagnose which wheel sensor it is, and if there's more to my issue, I now have some help with your post. Thanks a BUNCH :nice:
  4. I don't know if the 99 up mustangs have the same ABS diag port but you really don't need a scanner. You can use a jumper wire to jump the (If I remember right) the white/orng to the blk ground and count the abs light flashes. I have heard you can use a EEC-IV code scanner and I have one for my Fox but used the jumper wire method first.
  5. Thank you so much for this post!! My car started exactly like you said and contiued until it stayed on all the time. I work at a dealership and they told me that I'd probably need a new module.. This has been a great help!

    How long have you had the reworked module in your car?
  6. Hey all you guys,

    I am the publisher of the YouTube video. If you have any comments or suggestions I will be happy to add them to the annotations in the video.

    OP: Your post mirrors my problem exactly: intermittent lights and an IDS scanner unable to communicate with the ABS module. In these cases swapping out the control module itself is usually a good fix. It worked for me and there were other appreciative people replying to my video.

    Disclaimer: I am on not the original creator of the method to fix this.... UltraShock2112 is. I just built on his idea and made a video to show the rest of us monkeys how to do it.

    @1987StangMan It is possible to measure the impedance on certain pins of the ABS control module harness. I don't have the link handy but know that if the impedance is too high or too low on certain pins it means the control module is dead and must be replaced.

  7. Hey, I have had the "new" module (the one from a 80k 2000 GT) in my 2002 GT for about 10 months and 15,000 miles so far. No complaints!
  8. Good stuff thank you for the info.. My module has been in the crapper for a few years now and I've just been driving w/o ABS brakes.. Hell some of my old cars didn't have power brakes whose to complain :)

    I'm going to follow the step by step to double check the wheel sensors and then yank off the module and send it out to be fixed once I determine if that's it.. Thanks for spending the time to write it out for the rest of us...