Wheel speed sensor codes

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Prospect62

Registered
Hey guys, I have a persistent ABS light and "check traction control" light on my 1998 Mark VIII. I scanned the codes and got error codes for both the left and right rear wheel speed sensor, which from what I gather is a relatively common failure item.

I do find it odd that both the left and the right sensors have gone bad though...is this likely? Or could I have another issue such as a bad ABS module or corrosion in a connector somewhere?

Also, since the OEM Ford parts are no longer listed as available, can anyone recommend a trusted brand for replacement? I'd like to only have to do this job once.

Thanks!
 
I didn't see this until now, I'll move it to the brake area. The module is probably ok if your speedometer and odometer are still working. You might want to check the wires to the sensors though. Search Bruce Budnick for his info, he might have some available. Maybe you should buy one first just to check if one code goes away after replacing.
 
Thank you for the info sir. I've been buying and selling with Bruce for a couple weeks now, seems 98 sensors are one-year only items (figures) and command quite a premium. I will inspect everything I can to rule out dirt, corrosion or damaged wires before I buy replacements. I'm hoping maybe it's something I can repair.
 
Man I got under the car yesterday and found the rear speed sensors and they look impossible to swap out. I did notice that the tone rings mounted on the CV shafts are VERY rusted - I wonder if that has anything to do with both sensors reading bad?
 
Prospect62 said:
Man I got under the car yesterday and found the rear speed sensors and they look impossible to swap out. I did notice that the tone rings mounted on the CV shafts are VERY rusted - I wonder if that has anything to do with both sensors reading bad?
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The important thing about the tone rings is the gap. Not only a consistent gap from the sensor to the OD of the ring but the gaps between the teeth of the ring. Rust is not uncommon but shouldn't be a problem unless it interferes with the gap - both between the teeth and the OD of the tone ring.

The rear sensors are bolted to the differential housing and yes they can be very difficult to remove. It is best to clean with a wire brush and soak the area with PB Blaster or equivalent daily for several days before trying to remove them. Rounding off the bolt head or twisting the bolt off are all too common when attempting to remove them. Impact wrenches (pneumatic, electric or battery) should be avoided. Careful application of heat and/or the use of a manual impact driver can be helpful.
 
driller said:
The important thing about the tone rings is the gap. Not only a consistent gap from the sensor to the OD of the ring but the gaps between the teeth of the ring. Rust is not uncommon but shouldn't be a problem unless it interferes with the gap - both between the teeth and the OD of the tone ring.

The rear sensors are bolted to the differential housing and yes they can be very difficult to remove. It is best to clean with a wire brush and soak the area with PB Blaster or equivalent daily for several days before trying to remove them. Rounding off the bolt head or twisting the bolt off are all too common when attempting to remove them. Impact wrenches (pneumatic, electric or battery) should be avoided. Careful application of heat and/or the use of a manual impact driver can be helpful.
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In your experience (or have you heard anecdotally) of a good wire brush and brake-cleaner scrub down of the tone ring teeth making a positive impact where a sensor reads bad? These things are so rusty (and it's funny because it's like the only rust on the whole car) that I wouldn't be surprised if the metal's magnetism or the physical gap has changed. The car only has 49,000 miles on it how could BOTH sensors have gone bad? It's a long shot, I know. I just don't want to spend $300 on new (used) sensors and go through what looks like absolute hell to change both sides for it to still not work.

Thanks for the tips on replacement, but I am curious - where does the connection terminate? It looks like the wire went up into the body?

This seems like such a trivial problem to have and at the end of the day, I can live without ABS and traction control (in fact I prefer it that way). But hearing and seeing those ridiculously annoying error messages every time I start the car and having to acknowledge them really sucks and it ruins what would otherwise be an almost perfect car.
 
Prospect62 said:
In your experience (or have you heard anecdotally) of a good wire brush and brake-cleaner scrub down of the tone ring teeth making a positive impact where a sensor reads bad?...

... where does the connection terminate? It looks like the wire went up into the body?
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Over the years (not necessarily limited to a Mark VIII)... maybe a couple times I've seen cleaning the ABS ring have a positive impact. Remember that the ABS sensor is a magnetic pickup and rust is a ferrous material which implies it could interfere with the proper operation of the ABS. Certainly a minority of the time, but hey, it's worth a try!

I recall the harness connections being in the trunk behind the trunk liner.
 
Maybe if you do get a new sensor to test it, just plug it in before removing the old one to see if the code goes away first before attempting to remove the old one. I'm not sure, but you might need to hold it close to the ABS ring when you run the code.
 
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