Hi folks,

I've taken my first drive on the ice and my anti-lock does not appear to be working. I locked up the brakes a few times in a safe place and there is no pedal pulsing and the ABS light does not come on. The wheels lock up and this big old truck slides real well though.

Needless to say, I'd like to have the ABS working. The ABS light comes on at start up, so I presume that I have ABS, although I'm pretty sure it's just rear wheel ABS. The original window sticker does not indicate 4 wheel ABS so that means just rear wheel ABS right?

Could this be caused by the speed sensor on the rear axle I keep reading about on other threads? If so, why aren't my ABS and Brake indicator lights on all the time?

Any help on where to start checking would be appreciated.

Thanks,

Dan

 

Well, i hope this helps....

I have a 97 and when my rear speed sensor broke, I had a constant yellow ABS light on. But here's the catch.....I didn't know because my bulb was burnt out. I replaced the bulb and there was my symptom. I replaced the rear speed sensor and ....snap, I had antilock brakes. But, you say that you get the bulb check ABS light on start-up. So, unless 1998 is different than mine, your ABS symptom isn't communicating with the PCM. So your ABS system doesn't know you have a problem.

I would just unplug everything and plug back in. The ABS pump is on the driver's side next to the fuse box under the hood.

I don't have a 98, so maybe your PCM communicates differently than mine. Good luck.

Tom

 

There are two anti lock systems available. RWAL, which is rear only, and 4WAL which utilizes all four wheels. Sure you got 4WAL?

;DANTI-LOCK BRAKES: System designed to allow the driver to hit what they are aimed at.

 

I might have the same problem.... Not all of the time but sometimes when I first start it up and slowly roll it I barely touch the pedal the brakes lock up and the truck jerks. this will only happen for a little while until I start moving and it wont happen anymore. abs light comes on during start up ... but will not stay on ???

 

Dec, I'm relatively new to this site, and to Dodge CTD, but I teach auto body for a living. Anyway, most abs systems have a wheel speed sensor. On some pickups, the sensor will not be on each wheel, as the rear sensor will be located on the rear axle carrier (pumpkin). Inside the pumpkin will be located a "tone ring" or what looks like a gear with teeth, but no chain. The speed sensors monitor wheel movement, not vehicle speed. When you abruptly (panic stop) change the movement of the tires, the sensors should signal the ECM to start pulsing the brakes. If there are no codes present, and your ABS amber warning light goes off after startup, you can rule out any electrical problems. The only other possibility could be that you only have rear ABS, and that your rear wheels are not locking up completely......But, that is just my opinion, and opinions are like other orifaces on our body, we all have at least one ;D

 

I've found on my truck that the anti-lock brakes will NOT activate on ice. They'll work on snow/slush/mud, but if I'm on a sheet or patch of ice they just lock up. Maybe it has something to do with there not being enough friction for the sensor's to realize the wheels are locked?? ??? My 3/4 ton Chevy (RWAL) does the same thing. Am I close on this ya'll? :- That's about the only thing I can figure-
Justin

 

They should work anytime there is a lock up or panic type stop initiated by you, ice, snow, slush, whatever. I know mine do work on all those surfaces. I'll look into it a school tomorrow, see what I can find out.

 

I've always been able to lock the rear wheels on my truck even when the ABS was supposedly in good working order. Never trusted it.

 

Thanks for all the replies,

It sure felt like all 4 wheels of the truck were locked when I tested it and still no ABS. Maybe the back brakes aren't locking and it was locking it up through the drivetrain (I was in 4-wheel drive with a manual trans)? My E-brake is almost at the end of it's travel so maybe I need to do the manual adjust on the drums. I won't be getting to that until after the holidays but I'll post if that works.

Does anyone know how to tell whether you have 4 wheel ABS vs. RWAL easily?

Thanks,

Dan

 

Dec,

Talked to some of the service intructors at school this morning, They were under the impression that it IS possible to lock up the wheels with an ABS system and not engage the anti-lock feature. It goes like this:

The wheel sensors are monitoring vehicle movement. You initiate a panic stop, or you lock up your wheels. It is POSSIBLE, given the right situation, that you could lock up all four wheels at exactly the same time, in which case you would "FOOL" the ecm into thinking you had simply come to a stop. The ecm and abs system is designed to read wheel movement differences between the 4 wheels. In the event that one or more locks up at a different rate----the system should pulse the locked up wheel.

ABS systems are getting more and more sophisticated as time progresses. A faulty system should register on the ecm in the form of a code. The newer systems will not allow fooling of the ABS system, because they have yaw and inertia sensors as well as movement sensors.

PS Look off your master cylinder for a proportioning valve, or check the front wheels for sensors.

 

[quote author=dingo link=board=5;threadid=23680;start=0#msg225531 date=1071718385]
I might have the same problem.... Not all of the time but sometimes when I first start it up and slowly roll it I barely touch the pedal the brakes lock up and the truck jerks. this will only happen for a little while until I start moving and it wont happen anymore. abs light comes on during start up ... but will not stay on ???
[/quote]Dingo your problem is related to flash rusting of the drums when the truck is parked causing the shoes to stick. If you pay attention you'll probably notice it's worse in humid or rainy weather. About the only thing you can do is realize it happens and do a couple of gentle stops before getting out on the road.

 

Hey Magnum, Do you suppose the fact that the transfer case was lock in 4wd that the ABS could not function? If he was in 2wd, then I would say there is a POSSIBLE PROBLEM. With a mechanial connection between the front and rear axle the abs would be functionaly useless.
Tom

 

Does anybody know if our ABS is disengaged/turned off when in 4 wheel drive? I know some vehicles ABS is disabled when you shift into 4x, some just when you shift into 4lo.
Justin

 

With 4 wheel anti-lock just the front ABS is disabled in 4wd

 

MNTom--good point, I'll check downstairs with the service instructors. I personally don't know.

But I'll find out......Magnum