ABS Brake Dash Light

[Denny]

Bruce,
My ABS dash light was on all the time and never went out. I had it checked out and it was a driver's side rear sensor. As Kevin mentioned, the ring and pinion had to be pulled to access the sensor. Had it replaced at Prevost in New Jersey. There are front sensors also, and as I understand it, are not as complicated to replace as the rears.

When replacing one rear, have both replaced. The labor is just a little more to do two as to do one. As I recall, it was around $1500.

The newer coaches have a different system and is not as difficult to change but our vintage coach, 1998 chassis on mine, the rears are a PITA to work with and costly.

Denny

[0533]

Hello Denny,

That is expensive. The sensors are just that, they do not affect the function of the ABS system?? If this is so then I think I will get rid of the light.

Its interesting though that Prevost does not consider this light malfunction a possible defect and or recall item. I guess it is because it does not affect the ABS system but does cause us to ignore the possible problem. I do not think that GM could get away with this.

This idiot light will be going dark unless it is important not to.

[truk4u]

Bruce,

In your Prevost manuals there should be an axle manual such as Eaton that is labeled ABS. You can check the blink codes (toggle switch and light probably in the steering bay) and identify which part is causing the problem. I had to do this once and it identified one of the sensors. I reset the system per the manual and never saw the light again. It's easy to do, just count the light blinks in order and refer to the manual.

[0533]

I have looked at this switch for months now and wondered what it was for. That is really interesting. I will look for the Eaton manual and give it a try.

Very interesting. thanks Tom.

[Jon Wehrenberg]

Bruce,

If the ABS light is on, for whatever reason, the antilock braking feature is disabled.

If the system is disabled you have to control lockup. If you sense a wheel or axle is locking you have to release brake pedal pressure because a locked wheel has substantially less braking force than a wheel still rolling but just below the point of lockup.

Is this critical on our coaches? If you are driving in slippery conditions it could prove vitally important in an emergency stop. It may be less critical in the desert Southwest. Early XLs did not have ABS.

[0533]

Jon,

So what you are saying is that even if the problem is a sensor and the light is on the ABS system is not operating, it is disabled when an idiot light comes on.

So what happens if I am able to reset the light using the Eaton manual and the blinker in the steering bay?

[Jon Wehrenberg]

If the ABS light is out, such as by resetting, the system has been restored.

It is not like you do not have brakes when the light is on. You have the same brakes you always had, but control of the wheel lockup is now your responsibility, and not the ABS so the braking technique you must use is different.

When ABS is functioning, and you need to make a maximum performance stop, just slam on the brakes with all you have and allow the ABS system to control the braking force at each wheel. I have never locked up my brakes or needed that kind of stop in my bus, but on a car with ABS you slam on the brakes and hold your foot down as hard as possible. You will hear or feel the brakes pulsing as the ABS works to keep the brakes from locking up, but at their maximum effectiveness.

Without ABS you, the driver have to modulate the braking force to prevent wheel lockup.

Loss of ABS does not mean less or defective braking, just a change in your braking technique depending on whether your ABS is functioning or not.

[0533]

At least I know this needs to be fixed. It really is a safety item and should be a recall item. I am still surprised that Prevost can get away with this if it is happening to most if not all shells of our vintage.

[aggies09]

I am in Dallas at Prevost today having my sensor(s) replaced. Same issue as you described, light came on sporadically at first then just started staying on all of the time. Troy Moody at Liberty told me exactly what Jon just described as to what works and doesn't work when the idiot light shows up.

[Jon Wehrenberg]

Bruce....whoa.

The loss of ABS is not a safety issue. Not in the least. It only means you as a driver have a responsibility of controlling your braking, and that you have not turned that responsibility over to a computer.

A while back one of the car magazines did extensive testing on ABS using professional race car drivers. They determined that a skilled driver could do a better emergency stop without ABS compared to an ABS controlled stop.

Cars that have stability control turned off can perform better in the hands of a professional driver than with it turned on.

I know we are not professionals. But these systems are installed primarily to protect passengers against inept drivers. If your light is on I doubt if you could tell the difference between a stop you make without ABS (as long as you are sensitive to wheel lockup) to one in which ABS is employed. You just have to recognize the two different braking techniques required.

I'll let the professional truckers here, all of which I'll bet have driven with and without ABS, chime in.