ABS light is on
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ABS light is on
Hey there,
My ABS light is on in my 94 F250, I read the whole section in the haynes manual and it told me how to replace the components but not how to diagnose them. Can anyone help me out here?
My brakes work fine (except the abs) it is just that the pedal goes to the floor easily, like there is no pedal pressure.
my thouths are it has to be a wheel speed sensor, a bearing or the abs sensor.
It is a 5 speed manual, 4x4, assuming rear abs only.
My ABS light is on in my 94 F250, I read the whole section in the haynes manual and it told me how to replace the components but not how to diagnose them. Can anyone help me out here?
My brakes work fine (except the abs) it is just that the pedal goes to the floor easily, like there is no pedal pressure.
my thouths are it has to be a wheel speed sensor, a bearing or the abs sensor.
It is a 5 speed manual, 4x4, assuming rear abs only.
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
If the speedometer is not working or not working properly then it the the vehicles speed sensor, and it should be located on top of the rear end. At least that is how it is on my F150. The speedo and the rear abs uses the same sensor. If you go to the parts store to get it tell them you want the abs sensor not the VSS, otherwise you will probably end up with a speed sensor for an older truck.
Lead Driver
Joined: Nov 2002
Posts: 9,556
Likes: 43
From: Concord, NC
There is a way to get the ABS light to flash codes which may help narrow down the problem. I don't know where it is on your year truck, but on my truck (87) it is near the emergency brake pedal, and is a black wire with an orange tracer. It has an open connector on the end, and you just have to momentarily short that wire to ground to get the light to blink codes.
Since your pedal is not very firm, I would think that it is an hydraulic problem rather than anything electronic. A bad wheel bearing wouldn't turn on the ABS light and the only ABS sensor is the wheelspeed sensor on the rear end. If you haven't tried bleeding the brakes already, that might be a good place to start. Begin at the right rear then move to the left rear, then right front, then left front, and don't forget to bleed the ABS valve on the driver side frame rail as well.
Since your pedal is not very firm, I would think that it is an hydraulic problem rather than anything electronic. A bad wheel bearing wouldn't turn on the ABS light and the only ABS sensor is the wheelspeed sensor on the rear end. If you haven't tried bleeding the brakes already, that might be a good place to start. Begin at the right rear then move to the left rear, then right front, then left front, and don't forget to bleed the ABS valve on the driver side frame rail as well.
Post Fiend
Joined: Jan 2005
Posts: 8,402
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In the RABS valve block ( on inside of left side frame rail about driver`s feet ) there are two solenoid valves. One of these valves allows fluid from the rear brakes into a chamber against a spring loaded piston. This happens when the system senses that the rear wheels are locked. It sounds to me that the valve has failed open, allowing the pedal to sink. If this is the case you will either have to disable the RABS valve or replace it. A reman. costs about $125.00 plus core. If you look at the valve block you will see a large hex plug on the end towards the front of the truck. If you unscrew this you can remove the spring inside and replace the plug. Pump the brake pedal a few times. If the pedal stays up you have found the problem. You will not, of course, then have ABS. You can leave it like that or replace the valve block and bleed then system. If you do a search at raybestos.com you should find fault finding for Kelsey Hayes RABS systems. Hope this helps.
Mountain Pass
Joined: Feb 2007
Posts: 121
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From: Central Georgia
Is the weak pedal a symptom of the ABS coming on? Or was it a problem before the ABS light came on?
If it's a symptom that appeared after the ABS light came on, Lazy K has some solid advice for diagnosing the problem. Autozone has a reman unit for $98 plus a $61 core charge.
If the weak brake existed before the ABS light came on, I'd start with the RABS sensor and replace that first. It's easy to replace (less than 5 minutes) and inexpensive (less than $20). My 1993 F-150 had the ABS light come on and just needed a new sensor. My brother's 1996 F-150 had his ABS light come one and it just needed a new sensor. This isn't an uncommon problem in these year models. Then I would focus on why you have a weak pedal.
Link for changing the RABS Hydraulic Control Valve: http://www1.autozone.com/az/cds/en_us/0900823d/80/0a/a4/10/0900823d800aa410/repairInfoPages.htm
Link for changing the RABS sensor: http://www1.autozone.com/az/cds/en_us/0900823d/80/0a/a4/2e/0900823d800aa42e/repairInfoPages.htm
If it's a symptom that appeared after the ABS light came on, Lazy K has some solid advice for diagnosing the problem. Autozone has a reman unit for $98 plus a $61 core charge.
If the weak brake existed before the ABS light came on, I'd start with the RABS sensor and replace that first. It's easy to replace (less than 5 minutes) and inexpensive (less than $20). My 1993 F-150 had the ABS light come on and just needed a new sensor. My brother's 1996 F-150 had his ABS light come one and it just needed a new sensor. This isn't an uncommon problem in these year models. Then I would focus on why you have a weak pedal.
Link for changing the RABS Hydraulic Control Valve: http://www1.autozone.com/az/cds/en_us/0900823d/80/0a/a4/10/0900823d800aa410/repairInfoPages.htm
Link for changing the RABS sensor: http://www1.autozone.com/az/cds/en_us/0900823d/80/0a/a4/2e/0900823d800aa42e/repairInfoPages.htm
Thread Starter
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Senior User
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Guys thanks for all the feed back I have a few areas to test now.
Unfortuantly I can't tell you what came first as I just got the truck and these were symptoms that I inherited so I will have to track it down one shot at a time.
Any other ideas keep them coming and if the weather stays nice up here in NY I will be crawling under her soon.
Unfortuantly I can't tell you what came first as I just got the truck and these were symptoms that I inherited so I will have to track it down one shot at a time.
Any other ideas keep them coming and if the weather stays nice up here in NY I will be crawling under her soon.
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Post Fiend
Joined: May 2004
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From: Lakewood, Ohio
buy a manual if you do not already have one.
the abs light is on because you have air in the system.
start at master cylinder and work out to the wheels, checking everything.
the abs light is on because you have air in the system.
start at master cylinder and work out to the wheels, checking everything.
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I did buy the haynes manual and am not very impressed by it. It tells you how you replace the part if you know that is what needs to be done. But it doesn't really tell you how to diagnose the issue.
I plan to be underneath is shortly, I will post the update of what I find.
I plan to be underneath is shortly, I will post the update of what I find.
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I stopped by my local parts store today with the intent to buy the RABS speed sensor, it is only $10.00. I was telling the guys there about it and they suggested just pulling the fuse and seeing what happens.
So I did, and now the ABS light flashes twelve times and pauses then flashes 12 again. I am not sure if that is a code or just a reminder the fuse is missing.
The two days of rain here has put a damper on me crawling under the truck and pulling the spring out but will do that as soon as weather permits.
So I did, and now the ABS light flashes twelve times and pauses then flashes 12 again. I am not sure if that is a code or just a reminder the fuse is missing.
The two days of rain here has put a damper on me crawling under the truck and pulling the spring out but will do that as soon as weather permits.
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Abs light Stays on
Originally Posted by quicklook2
buy a manual if you do not already have one.
the abs light is on because you have air in the system.
start at master cylinder and work out to the wheels, checking everything.
the abs light is on because you have air in the system.
start at master cylinder and work out to the wheels, checking everything.
Post Fiend
Joined: May 2004
Posts: 11,289
Likes: 6
From: Lakewood, Ohio
anytime i had a leak in the rear brakes both the abs and brake warning light came on and after fixed and bled they both went off.
with a leak in the front line only the brake light came on.
the abs probably knows the circuit does not have pressure.
with a leak in the front line only the brake light came on.
the abs probably knows the circuit does not have pressure.