ABS idiot light in the dash just started coming on

[bodkin1]

I was driving home after doing some running around out of town today, and all of a sudden the ABS light came on. Hit the brakes gradually and the brakes were still functioning as normal, pedal didn't go flat to the floor.
Pulled into a roadside park to look the truck over. Checked the master cylinder, it was full. Checked the insides of all 4 wheels for any leaking brake fluid, they were bone dry. I shut the truck off after pulling in to hopefully reset the light, started the truck after maybe 3 minutes and the light finally shut off, and continued on driving. And wouldn't you know it, after a minute the ba$tard lit up again...
As far as I am concerned, if it still drives and stops as normal, I ain't going to worry (only complaint will be that distracting light). But should I worry in the long run is my biggest question.

 

[bodkin1]

Well I let it sit for an hour and a half, and took it up and down the highway about 6 miles... it stayed off. Guess I didn't let it sit long enough for it to fully reset.

 

[Steeda04SVT]

Mine has been coming on all the time once I hit 40-45 mph. Been irritating as hell. Still trying to find a solution.

 

[Explorin94]

Do you have 4 wheel or 2 wheel ABS? If it is just 2 wheel ABS I would take the dash apart and pull the bulb. If it is 4 wheel ABS you will need to take it to a shop that has the capability to read ABS codes. You may find that the sensor in the back axle is bad or you have a failing wheel bearing up front.

 

[powerranger262]

So I agree with the sensor in the axle (speed sensor), but not at all with taking the dash apart to pull the bulb. Really?

 

[bodkin1]

Update- since my last post it has started coming on, and staying on. However on occasion if I let it sit a while and then restart it, it will actually stay off. Went on a 30 mile roundtrip Saturday and it didn't come on once.

 

[bodkin1]

Do you have 4 wheel or 2 wheel ABS? If it is just 2 wheel ABS I would take the dash apart and pull the bulb. If it is 4 wheel ABS you will need to take it to a shop that has the capability to read ABS codes. You may find that the sensor in the back axle is bad or you have a failing wheel bearing up front.

2 wheel.

 

[Earl43P]

2WABS uses the VSS sensor on top of the rear axle. It's a cheap part (~$20) and one 10mm bolt holds it in, along with an o-ring that makes it a little hard to pull out of the bore (just wiggle it).

However, I HIGHLY doubt that a 2002 4WD model only has 2WABS. Look at the ABS module under the hood (it has brake lines running to it). See if the connector has these color wires going into it from the front wheel sensors:

YE/BK (yellow wire with a black stripe)
YE/RD
TN/BK
TN/OG

If it has those wires, it is 4WABS.

The rear sensor's wires are LG/BK and RD/PK.

That complicates your ABS light issue because there are front wheel speed sensors (near the hub unit bearing). Basically, just look for a wiring harness to each front hub = 4WABS. One of those front sensors could be bad. When that happens, you typically get an ABS activation (brake pedal pulsates) when turning at low speeds and pressing the brake.

Considering the price of front hub sensors, it may be worth having a Ford dealer pull your ABS code(s) for a proper diagnosis. Alternative is if your are handy with a meter and your meter has a Hz function, test the sensors by connecting to each sensor's wire pair and spin that wheel. Compare readings. You can also do it on Ohms and Mv, but it will be far less precise than Hz. Most digital meters don't have the Hz function.

Or just pull front sensors from a junkyard 2000+Ranger or 98+Explorer and replace the rear VSS. Your call.

 

[Explorin94]

So I agree with the sensor in the axle (speed sensor), but not at all with taking the dash apart to pull the bulb. Really?

Yeah! Really! I didn't look at the year of his truck. The 89-97 dashes can have the ABS bulb removed fairly easy. The newer trucks I don't know.

 

[Steeda04SVT]

Yeah mine still comes on and just recently put 4 new wheel bearings up front with new rotor/hub assy and pads. Only thing not new is the calipers. RABS sensor is new, ABS Module has been replaced. RABS Proportioning Valve has been replaced and still it comes on.

 

[bodkin1]

2WABS uses the VSS sensor on top of the rear axle. It's a cheap part (~$20) and one 10mm bolt holds it in, along with an o-ring that makes it a little hard to pull out of the bore (just wiggle it).

However, I HIGHLY doubt that a 2002 4WD model only has 2WABS. Look at the ABS module under the hood (it has brake lines running to it). See if the connector has these color wires going into it from the front wheel sensors:

YE/BK (yellow wire with a black stripe)
YE/RD
TN/BK
TN/OG

If it has those wires, it is 4WABS.

The rear sensor's wires are LG/BK and RD/PK.

That complicates your ABS light issue because there are front wheel speed sensors (near the hub unit bearing). Basically, just look for a wiring harness to each front hub = 4WABS. One of those front sensors could be bad. When that happens, you typically get an ABS activation (brake pedal pulsates) when turning at low speeds and pressing the brake.

Considering the price of front hub sensors, it may be worth having a Ford dealer pull your ABS code(s) for a proper diagnosis. Alternative is if your are handy with a meter and your meter has a Hz function, test the sensors by connecting to each sensor's wire pair and spin that wheel. Compare readings. You can also do it on Ohms and Mv, but it will be far less precise than Hz. Most digital meters don't have the Hz function.

Or just pull front sensors from a junkyard 2000+Ranger or 98+Explorer and replace the rear VSS. Your call.

Yes it has 4WABS. I think this weekend I will try replacing the sensor in the rear end, as it is the cheapest. As for the front sensors, can it be possible to test them with a DMM? And what is the procedure for that? Test it at the plug behind the front bumper?
Oreilly has the sensors for about $135, however foud them on Ebay for less than $50.

 

[Earl43P]

"One of those front sensors could be bad. When that happens, you typically get an ABS activation (brake pedal pulsates) when turning at low speeds and pressing the brake."


^ If it isn't doing that ^ (try both directions in a parking lot) I'd replace the rear sensor.

You can measure the ohms and spin each front wheel and watch it change or use Mv. Hz would be ideal, but most meters don't. If both sensors act the same, reading ohms or Mv, I'd say they are good.

Should you do that test on the fronts, have your girl take a video and submit it. My expectation is that the Mv will read zero until you spin, then you'll see it pulse/increase. Not sure what faster spinning will do. Ohms, I expect you to see "some" resistance, then when you spin the tire, it'll "change". How much? You tell us when you're done.

 

[bodkin1]

"One of those front sensors could be bad. When that happens, you typically get an ABS activation (brake pedal pulsates) when turning at low speeds and pressing the brake."


^ If it isn't doing that ^ (try both directions in a parking lot) I'd replace the rear sensor.

Yep that's what I was thinking, when I make a slow turn into my driveway (from either direction) I get no pulsating whatsoever. Good thing it appears to be the rear sensor, it's not even $20 at Oreilly's. Will replace it and give an update.

 

[Earl43P]

http://www.explorerforum.com/forums/showthread.php?t=306097 says this about the front sensor resistance:

I put a multimeter on each sensor and tested the resistance, and they were withing 0.01 Ohm of each other. (0.406 and 0.416).


http://www.explorerforum.com/forums/showthread.php?t=201425 says

"Front right sensor — 0.270–0.330 k Ohms
Front left sensor — 0.270–0.330 k Ohms
rear speed sensor — 0.8 and 1.4 k Ohms"

I've read a bunch of Explorer threads about the front sensor being part of the hub unit bearing. I removed each sensor on my old 2000 4wd and used the hole to pump fresh grease into the bearings. Not sure if they are sold separately, but they seem to break in the bore if removed roughly. I finessed mine out easily.

Virtually every thread recommends replacing the VSS/ABS Sensor on the rear axle first, so I bet that works for you. I've had fun reading up on it, if nothing else. Good luck!

 

[bodkin1]

I just replaced the rear sensor, the light still stays on. I am probably betting it is one of the front sensors. I am thinking maybe the driver's side one, when the light first came on the ABS would kick in whenever I made a left turn...

Will look at replacing it in a few weeks probably... might as well replace the whole hub while I am at it. Found a pair of hub/sensor units (for both right and left sides) on Ebay for only $99.