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Hey folks, I recently replaced my front rotors and disc brakes on my 2007 F150 RWD. Once doing so, immediately I had an ABS failure. Let me explain what I’ve done thus far and the symptoms I’m seeing.
The Symptom – with everything connected (all ABS sensors, etc.) when I start the vehicle, no lights are on and everything is normal. When I back out of my driveway, everything stays normal. However, when I go forward and press on the brakes, I can hear, and feel, the ABS system pulsating and I’m getting uneven braking when this happens also. Speed is not a factor, this behavior happens whether travelling fast or slow. After 60s – 180s, the ABS system will disable itself and turn on the ABS light. From that point forward, the brakes work fine and there is no noise or pulsating, just very even and good braking, but I also then don’t have ABS, obviously. I can also remove the fuses, and/or unplug one of the ABS sensors forcing the system to disable itself and again the brakes are fine.
I’m assuming I have something wrong with my front sensors or rotors since that is where I worked last. I have tried to measure the two front sensors with a DMM in Ohms and DC mV and I get no measurement on either with either setting while spinning the wheels or otherwise.
My question – I’m assuming the sensor is just a magnet sensing the gear like motion of the inside of the rotors and thus should be generating some sort of DC voltage, not resistance? What am I doing wrong in my diagnosis? Also, is it possible that the rotors I purchased from my local retailer are the wrong ones/type?
BTW – I had to replace my rotors and pads because the warping had become so bad I was concerned for my safety when stopping.
Thanks in advance, always appreciate your insights and advice.
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If you have a CEL, start by pulling any codes there.
My next step would be to hook up a scanner that can access your vehicle’s ABS module. Verify that the speed sensors are functional (spin the wheels and watch for a reading on the scanner). Then access the module and activate the solenoids while listening for engagement (sounds almost like a short fuel pump buz).
Hope this helps.LAR1969 – thanks for the quick reply. Sorry can you plz elaborate on what you mean by this (activate) “Then access the module and activate the solenoids while listening for engagement (sounds almost like a short fuel pump buz).” The short fuel pump buzzing is what I’m hearing when I first start driving until the ABS turns off.
Do your ABS sensors have an “air gap” adjustment, which sets the clearance distance between the pickup heads and discs, or do they just bolt in solidly?
[quote=”mx4cc904″ post=140796]LAR1969 – thanks for the quick reply. Sorry can you plz elaborate on what you mean by this (activate) “Then access the module and activate the solenoids while listening for engagement (sounds almost like a short fuel pump buz).” The short fuel pump buzzing is what I’m hearing when I first start driving until the ABS turns off.[/quote]
So did you say that you have a check engine light (CEL) on?
Ok, so with a scan tool that can access your ABS system (i.e. factory scan tool), “activate” would also mean command them on/turn them on. (Assuming they work similarly across most makes. I am sure someone will correct me if I am wrong). When you turn them on using the scan tool, you can hear them working if you are standing in the general area of the unit. To me, the sound reminded me of a fuel pump buzz but shorter in duration.UPDATE – ISSUE RESOLVED – I rode around for several weeks with this issue. I finally paid for the Torque PRO app on my Android phone which told me which ABS sensor was failing. In this case it was the Driver’s side front (I suspected it was one of the two front units). I removed the wheels, and very scientifically measured the ABS ring on each of the new rotors I had purchased. No surprise, the driver’s side ring was offset from the inside edge of the rotor MORE than the ABS ring on the passenger rotor. I removed the suspect rotor, took it back to AutoZone where they very graciously gave me a new rotor. Once I put the new rotor on (for a second time), the issue was resolved! Thanks all that replied.
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