ABS not working
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Senior User
Joined: Jan 2003
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From: Canyon Lake
ABS not working
my 99 f350 has ABS but, its not working. I have checked the fuses and they are all ok.
the light on the dash does come on then out at start-up like it should.
I did a search and really didn't find anything about the system. Does anyone know where the sensor are on the truck. Also a diagram would be a a great help for tracking down the system.
the light on the dash does come on then out at start-up like it should.
I did a search and really didn't find anything about the system. Does anyone know where the sensor are on the truck. Also a diagram would be a a great help for tracking down the system.
Postmaster
Joined: Dec 2010
Posts: 2,951
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From: Gary,Indiana
Well you have one sensor on each front wheel hub and 1 on the diff. I have the same problem but I need to know is what the ohmns range should be on these sensors so I can unplug and check before I start throwing parts at it. And is the range of the front different than the back 1? And to be honest I'll bet your or my problem is sensor or the plug that plugs into the sensor. Very rarely is it anything major.
Post Fiend
Joined: Sep 2003
Posts: 6,096
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From: Mesa AZ
Not all trucks have 4 wheel ABS...you will need to check your '99 to see if there are sensors on the front wheels to know for sure. Each front wheel will have a sensor (if equiped with 4 wheel ABS) then the VSS does double duty in the rear diff (as a speed and ABS sensor)
Postmaster
Joined: Dec 2010
Posts: 2,951
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From: Gary,Indiana
That usually means the system is working fine. How do you know your ABS is not working?
Not all trucks have 4 wheel ABS...you will need to check your '99 to see if there are sensors on the front wheels to know for sure. Each front wheel will have a sensor (if equiped with 4 wheel ABS) then the VSS does double duty in the rear diff (as a speed and ABS sensor)
Not all trucks have 4 wheel ABS...you will need to check your '99 to see if there are sensors on the front wheels to know for sure. Each front wheel will have a sensor (if equiped with 4 wheel ABS) then the VSS does double duty in the rear diff (as a speed and ABS sensor)
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
My e99 has the sensor on the rear diff on top of the pig. Would the VSS still play a role in the abs ? Do you know what the ohmns should be on the sensors and the vss sensor ? I know on big rigs and trailers the abs sensors should be between 500 ohmns and 2000 ohmns. But on these little trucks I have no clue.
Lead Driver
Joined: Jun 2003
Posts: 8,298
Likes: 25
From: Damon (South East Texas)
Front ABS Sensor Ohm Readings across the Sensor End connection
4x2 F250/350: 2,000-4,000 ohms
4x2 F450/550: 650-800 ohms
4x4 F250/550: 650-800 ohms
Rear ABS Sensor (VSS) Ohm Readings
All: 800-3,500 ohms
I also test ABS sensors on tractor trailer rigs and vehicles by setting my DVOM or Analog meter to its low AC volts scale and test for voltage while quickly spinning the wheel/hub assembly. Since they are adjustable on the larger rigs, it is usually a matter of resetting the clearance of the sensor or cleaning the ring.
4x2 F250/350: 2,000-4,000 ohms
4x2 F450/550: 650-800 ohms
4x4 F250/550: 650-800 ohms
Rear ABS Sensor (VSS) Ohm Readings
All: 800-3,500 ohms
I also test ABS sensors on tractor trailer rigs and vehicles by setting my DVOM or Analog meter to its low AC volts scale and test for voltage while quickly spinning the wheel/hub assembly. Since they are adjustable on the larger rigs, it is usually a matter of resetting the clearance of the sensor or cleaning the ring.
Postmaster
Joined: Dec 2010
Posts: 2,951
Likes: 4
From: Gary,Indiana
Front ABS Sensor Ohm Readings across the Sensor End connection
4x2 F250/350: 2,000-4,000 ohms
4x2 F450/550: 650-800 ohms
4x4 F250/550: 650-800 ohms
Rear ABS Sensor (VSS) Ohm Readings
All: 800-3,500 ohms
I also test ABS sensors on tractor trailer rigs and vehicles by setting my DVOM or Analog meter to its low AC volts scale and test for voltage while quickly spinning the wheel/hub assembly. Since they are adjustable on the larger rigs, it is usually a matter of resetting the clearance of the sensor or cleaning the ring.
4x2 F250/350: 2,000-4,000 ohms
4x2 F450/550: 650-800 ohms
4x4 F250/550: 650-800 ohms
Rear ABS Sensor (VSS) Ohm Readings
All: 800-3,500 ohms
I also test ABS sensors on tractor trailer rigs and vehicles by setting my DVOM or Analog meter to its low AC volts scale and test for voltage while quickly spinning the wheel/hub assembly. Since they are adjustable on the larger rigs, it is usually a matter of resetting the clearance of the sensor or cleaning the ring.
You are like the Shell Answer Man. I have a feeling it is one of sensors and since I have been spending alot of time laying under my truck lately I think I'll also see if I can't fix that pesty little yellow light on the dash ABS (It only goes on when I start rolling) I have been driving around with it on for about 3mths. It is always easier for me to start by checking sensors and leads with a DVOM. Besides I don't have AE or a scan tool for abs. Fixing abs on tractor or trailers is alot easier than these smaller trucks. Maybe because I have worked on more big rigs. I should have known you work on tractor/ trailers actually is there anything you don't work on. LOL
Thanks Ed
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On my truck I had a speedo that would not respond when you first start out, and then a second or so later it would jump up, and the ABS light would go on. I could be wrong but if the rear sensor doesn't work, then it will use the ABS sensors in the front to run the speedo. I replaced the VSS and it has been great since. I think it was like 28 bucks from Ford. It did not do it all the time, So I ran it till it did, good bad or other wise I have learned that Fords just throw codes some times... You just have to know what ones are the ones to worry about.
Lead Driver
Joined: Jun 2003
Posts: 8,298
Likes: 25
From: Damon (South East Texas)
You're quite welcome Ed 
I make all this crap up as I go along.
Seriously, I have a Ford manual on dvd loaded in my laptop for quick access.
Growing up on a farm and losing my dad when I was 9 gave me a lot of incentive to be versatile. I was also blessed with an inquisitive nature and alot of caring individuals that took the time to show me things they knew how to do. I'm just trying to pass on the gifts that were given to me.
I make all this crap up as I go along.
Seriously, I have a Ford manual on dvd loaded in my laptop for quick access.
Growing up on a farm and losing my dad when I was 9 gave me a lot of incentive to be versatile. I was also blessed with an inquisitive nature and alot of caring individuals that took the time to show me things they knew how to do. I'm just trying to pass on the gifts that were given to me.
Lead Driver
Joined: Jun 2003
Posts: 8,298
Likes: 25
From: Damon (South East Texas)
I agree to a certain extent, but nowadays ABS is a larger part of a balanced braking system. Without a proportioning valve like the older vehicles, the ABS carries that responsibilty.
I had the rear sensor go bad on a '00 Explorer Sport and would cause the rear brakes to lock and tires skid during hard braking. This, in turn, would put you in a ditch. I replaced the sensor and balanced braking was restored. That $20 part was a difference betwen and bad day and a good one. It was my wife's vehicle and that made fixing it all more the important.
I had the rear sensor go bad on a '00 Explorer Sport and would cause the rear brakes to lock and tires skid during hard braking. This, in turn, would put you in a ditch. I replaced the sensor and balanced braking was restored. That $20 part was a difference betwen and bad day and a good one. It was my wife's vehicle and that made fixing it all more the important.
Postmaster
Joined: Dec 2010
Posts: 2,951
Likes: 4
From: Gary,Indiana
I agree to a certain extent, but nowadays ABS is a larger part of a balanced braking system. Without a proportioning valve like the older vehicles, the ABS carries that responsibilty.
I had the rear sensor go bad on a '00 Explorer Sport and would cause the rear brakes to lock and tires skid during hard braking. This, in turn, would put you in a ditch. I replaced the sensor and balanced braking was restored. That $20 part was a difference betwen and bad day and a good one. It was my wife's vehicle and that made fixing it all more the important.
I had the rear sensor go bad on a '00 Explorer Sport and would cause the rear brakes to lock and tires skid during hard braking. This, in turn, would put you in a ditch. I replaced the sensor and balanced braking was restored. That $20 part was a difference betwen and bad day and a good one. It was my wife's vehicle and that made fixing it all more the important.
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