This article covers common problems known to activate the ABS light on some Ford products. Although the page is directed at specific issues with trucks and vans, the diagnostic tips work for any ABS light problem. At our fleet auto repair shop we've seen a large increase of anti lock light's illuminated on older F150, F250 pickups and cargo vans.
These vehicles set front wheel speed sensor codes for both the left and right front wheels. After performing a good visual inspection on several of the offending vehicles it was clear the sensors were all damaged where the wires attached to the head of the sensor.
Digging in and finding out what the cause of this common malfunction is a two-man operation. I had another mechanic turn the wheel from lock to lock while I observed the front wheel speed sensor and the movement of the wiring.
The wire harness is pulled tight when the steering reaches the end of its travel. This constant stress at the point it enters the wheel speed sensor is the issue causing the code to set, because it would eventually cause fractures in the wires, thereby turning on the Ford ABS light.
The diagnostic trouble code is for intermittent signal input detected by the BCM (Brake Control Module). If I had caught this problem a little earlier a simple re-routing of the harness would have provided more slack and prevented damage to the parts.
Note that replacing this ABS part requires the removal of the rotor on most Ford applications, but not all. This would also have avoided looking for the best price on replacement wheel speed sensors. On county vehicles you have to get three parts bids and submit the cheapest for approval. This extends the down time of the fleet vehicles, but assures efficient use of tax payer funds.
Wheel speed sensors are often the root cause of issues since they're exposed to harsh environments. Waekon makes an awesome universal plug in tester with all of the adapters included, but it's not cheap. So, you can probably guess my next move.
I decided to dig into the technical service bulletins to see if I could find a factory issued TSB related to Ford wheel speed sensor problems. Once again I wasn't disappointed by the factory reporting process and found three separate technical alert publications about specific Ford ABS light repairs.
The first one covered the problem mentioned
above. The second bulletin from All-Data, describes another common
anti-lock issue where the reluctor ring is either missing a
tooth or has been damaged by road debris. This is easy to see on a visual inspection.
If you have damaged or a broken tooth on the ring this can and will provide an intermittent signal to the front wheel speed sensor. A few different codes may set in this situation.
This reluctor ring looks like a gear with teeth on it. As the wheel rotates the teeth pass the magnetic wheel speed sensor and provides a reading that is translated into miles per hour.
When the brake computer see's the wheel is not moving it begins to pulse the brake calipers on that particular wheel. If it receives false information or erratic signals it will turn on the warning light to notify the driver of a problem with the ABS system.
This might also cause the ABS system to go active and pulse the brakes at low speeds when it is not necessary. The last bulletin describes a problem that I have not seen myself but is listed as a common problem with 1997 through 1999 Ford F 150 and F250 2 Wheel Drive models only.
The service publication describes a condition where the wheel speed sensor can work its way out of the spindle housing. If this backs out from vibration or slamming pot holes an increased air gap between the reluctor ring and sensor can also cause false wheel speed data and set codes for intermittent signals.
The sensor body should be flush with the spindle housing. I have not seen this problem, but I know people who have and maybe you will too? The ABS bulletin recommends replacement of the sensor.
After talking it over with a few technicians in my shop we agreed it was worth while trying to re-seat the sensor before replacing it. You do this by pushing it inward, and seeing if the problem is solved. If this doesn't work you can always replace the sensor at that point.
Note: On the left the Actron enhanced scan tool interfaces with the vehicles factory on-board diagnostics system
(domestic vehicles 1996 and up). It reads brake system and OBD II codes but make sure your vehicle is on the provided application chart. Equus makes a similar tool that's only a few bucks more that I talk about below.
When the anti lock brake light comes on it may set different codes. Most cars and trucks have a speed sensor for each wheel. But some older rear wheel drive vehicles will use one sensor for the drive axle like the WSS on the right. This part can go bad as well.
I have also seen metal particles from the differential cause signal problems. This can be build up on the magnet or heavy particles suspended in the fluid. But when the differential is torn up to this point you might have a more serious issue to deal with.
Wheel speed sensor codes are definitely the most common failures in these systems. However, knowing which sensor is having the malfunction is very important for speedy diagnosis. Professional grade brake scan tools are expensive and this made it difficult for do-it-yourself mechanics to diagnose and repair system failures.
There is an updated Equus scan tool, called the Innova 31603, on the market that will tell you why The amber ABS light is on. Make sure you check the vehicle coverage list provided. This scanner will work on most domestic vehicles and a few import cars from 1996 model year and up.
more information on the satisfaction level of this tool click on the
links and read the reviews from other do-it-yourself mechanics.
I've used both brands and they're about equal in coverage and performance.
This article is just one of the many that I supply on my auto repair news page. This has been one of the most popular destinations on this website, and I do add new articles about twice a month.
Give this ford abs light page a bookmark or share with a friend. Stop back to ask DIY car repair questions and check for updates.
If you have never done your own brake job I just posted a video that walks you through the process and includes some helpful tips for do it yourself mechanics. Take a look at the video of a front brake job.
Would you like to see just how easy it is to find technical service bulletins for your vehicle. This next video shows a screen capture of me actually using all-data to hunt down a auto repair bulletin.
Learn more about this do-it-yourself car repair website on the homepage. In fact this next link will take you to the Diy auto repair homepage.