I just purchased a 2000 F350 7.3L CC LB SRW with 120k on the clock. During the testrdrive the ABS light was on... no biggie, I got a steal on the truck. Then I noticed sometimes when I turn the truck on, the light is off, but once I get rolling the light turns on and stays on. In the summer there are 39.5 IROKS on it... my "crappy weather" tires are 37" TSLs and my winter tires are tiny Hakka snows. They are like 29" tall or something silly. Either way, the light would trip immediately or stay on.

During my inspection I had my buddy plug in his SnapOn scanner, and it registered as the speed sensor in the axle.

My speedo works. It isn't accurate due to the larger tires, but it moves just like any speedo. It is sensing speed, just not enough

Would replacing the speed sensor solve my problems? Is it really the speed sensor? If it was, wouldn't the speedo be acting up as well?

I would also like to correct the speedo, but I haven't been able to justify spending $200 for just that purpose.

Any help would be appreciated.

 

Yes, a VSS sensor problem will cause an ABS light, although that is usually accompanied by speedometer problems.

As a first step, remove the VSS sensor and clean it. See if that doesn't help.

 

Thanks. it is right on top of the diff right?

 

10-4 on the location

 

Before I go out there and soak it with WD40, what would you recommend?

 

[QUOTE=redford]Yes, a VSS sensor problem will cause an ABS light, although that is usually accompanied by speedometer problems.
QUOTE]

I had a VSS failier and speedometer worked fine

 

Another indicator combined with the ABS light would be whether or not your cruise control still works properly. Mine would engage but after a few minutes, it would disengage as if the engine had stalled and then re-engage with a kick in the pants acceleration to get back up to speed.

 

Cruise works fine.

Is WD-40 ok to clean it?

 

VSS sensor don't always affect cruise,occaisionally wound affect speedometer but would work again with restart

 

Like someone else said it may just need to be cleaned, It is basically just a magnet and gets metal shavings on it and gives funny readings. I myself would just replace it as they are not all that expensive and then you would know you should have a goodone in the there.

 

1. Your ABS/ VSS can be removed and cleaned with just a clean rag, no need for wd-40 or any other solvent, also carefully clean out the hole on top of the differential, lift the vehicle (place in neutral) and check the sprocket wheel inside the pumpkin for possible missing teeth or to see if it is loose.

2. The VSS (part # F85F-9E731-AA) can also be tested with an ohms meter, it should measure ~1.9 K-ohm or higher (lower than 1.9 requires replacement).

3. The VSS is a hall-effect sensor, connect a volt meter to the sensor connector and wave a piece of metal (pair of pliers or flat metal) about a half inch away from the sensor, and you will consistently see a variation in voltage, if no movement on the volt meter is observed, replace the sensor.

4. You also have the two front wheel ABS sensors, try cleaning them first, and carefully reinstalling them.

5. When the VSS sensor is malfunctioning, the PCM may try to get input from the TSS (turbine speed sensor, top of the transmission), and as it turns out, the same return wire is used by the OSS (output speed sensor, tail end of transmission), check these two sensors also, clean them and test them (1.10 K-ohm or higher). These are also Hall Effect sensors, so check for voltage as described in paragraph 3 above.

6. Pay attention to see if your ABS light blinks when you start the vehicle, just before it stays solid. If this is happening, count the number of blinks, as this is actually a code and the blinking means the vehicle is trying to communicate with you.

7. Last, if nothing above corrected the problem, I would start tracing RFI (radio frequency interference), one sure area is usually your fuel pump (wires running along side VSS wiring. ABS/VSS wiring is routed directly to the ABS module.

I hope this information works for you.

 

Dang...if this don't fix you up, you can't be fixed!! Nice post!

 

I guess there really isn't anything else anyone can say on that subject! Wow! Nice post.

 

HOLY CRAP!!!! IT'S AREA 51! TRANSFORMERS!!!!!


What he said. There are two "speed sensors" though that can be confused at the parts store. They don't look the same but they are listed almost the same. The one on the rear diff is listed as the "ABS speed sensor"....the one on the tranny is listed as the "Speed sensor" The rear one is the cheapest and easiest to replace...about $12.

 

Thanks for all the help.

Barney... that was quite an entrance. Welcome!