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ABS Warning light
Heading back from the Rockies to Kansas for Harvest my “ABS” warning light went off on the dash, as well as the DDEC code. I called Prevost & they said “Drive On, It’s probably a sensor, but there are drivers out there with that light on for 10 years and don’t get it fixed.” Well, I wouldn’t wait 10 years, but at least I could get back to KS.
I then turned the coach off, then turned it back on. But the light and DDEC code was still there, but went off within a minute. I checked the DDEC error codes and no faults were registered.
Do do you think it would still register if Prevost put their computer on it? Any other thoughts?
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12 Replies
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When the ABS light comes on it means the ABS system wll not interfere wiht an impending brake lock up that the ABS is designed to prevent. Your entire braking system will function however but without the ABS function.
Typically your description of the operation of the light is associated with one of the sensors being slightly out of position and needing to be tapped back into place, or in the worst case a failing sensor. If you are going to be anywhere near a Prevost service center is they can connect to your coach and the ABS system will display the fault. The bad news is a failed sensoir, the worst news is you have a vintage coach that has the bad sensor in the axle housing which means serious money to replace it.
If you lead a clean life and are very lucky the computer will reveal it is a steer or tag, or an external drive axle sensoir, in which case a light tap with a punch might be all it takes to make the problem go away.
A sensor out of position usually acts up when their is dampness so that is a good sign if that is when it happens. A bad sensor is easily verified by the technician because he will measure the resistance and if it out of the acceptable range he will replace it.
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Well, I’m hoping for the dampness view & that somehow it cleared up.
But I’ll be at Jeff’s in November & could stop by Prevost Nashville if Jeff doesn’t have the right equipment.
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Talk to Al, he had that very problem with his reared sensor. Don’t panic Tim, chances are it’s another wheel position and you may never see the light again.
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Prevost can plug in their lap top to determine which sensor is causing the light to go on. In our case the drive axle on driver side 90 +/- times. On passenger 3 hits.
The bad news about this sensor was installed inside the pumpkin housing. Some brain child believed it should always be in an oil bath or was an after thought making existing rear ends (aka 3ad members), usable. Great spot but very time consuming to replace defective sensors.
Oh, Prevost has a better idea…. Putting together a kit leaving the original sensors in place, replacing brake rotors, pads, seals. A new harness kit is installed which must be programed into your bus.
The original sensors are abandoned in place and capping the connection points. Two Prevost techs did the upgrade in about 4 hours one on each side. Cost was about $3000
Today they still have sensors in steer and drive axles installed on the outside and if a failure occurs changed in half hour.
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Thanks Al,
Light only came on that one time & it’s not returned …. Yet!
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On my coach there is a switch that controls an ABS diagnostic light on the upper left side of the steering compartment. If you flip the switch it will strobe the diagnostic code which will identify the sensor that is causing the issue.
One of my drive axle sensors in the pumpkin is complaining. It does not seem to disable the entire ABS system. The ABS function still works at least for the steering axle. I could hear it engage on a couple of occasions when I had to brake hard on a road with some gravel. It sounds like a machine gun with the pneumatic brakes engaging and releasing quickly. First time I heard it I thought “this sounds expensive” but it was just the ABS engaging.
Here is the problem ABS sensor in the housing of the differential.
It does seem accessible but I have not talked to Prevost about replacing it since my ABS system seems to work at least on the steering axle.
I did not catch the ABS light during the purchase inspection four years ago because someone had removed the indicator bulb on the dash (probably got tired of looking at it) and I did not know about the status indicator readout in the steering compartment. It has been a good coach but it is another thing to look at when buying – caveat emptor.
Gerald
Jeff and Lindsay
91 Marathon XL -
Gerald,
When Intalked to Prevost, they said a number of commercial bus drivers simply put a piece of tap of the red light and continue to roll for years…
I have the “lock / unlock” door/baggage light that stays on and sometimes flickers. I figure it a loose wire somewhere in the system, but I haven’t figured out where it is yet. I’m ready to put that piece of black tape over it 🙂
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Gerald – See Al’s post above, he had it done at Prevost.
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Tim, Gerald, there was a previous discussion of this on the Chassis thread pgs 30 and 33. Geo.
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1999 Prevost Liberty XL
This is what I found on my short trip to upper Wisconsin. On my way back the ABS light came on. During a detour through Milwaukee (boy that sucked), I had to make a sharp turn causing my left drive tire to catch a curb. This caused the ABS sensor to think that the tire was a different size causing the light to come on about 20 minutes after I hit the curb. By reading the anti-lock braking system bus maintenance manual (Manual #30) it showed me how to reset the code for the ABS. After reset and a short drive, light went out.
This is worth checking out if your light comes on and could save lots of money.
This is a FYI and something to try if your ABS light comes on.
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I have and use a reader to pinpoint ABS light codes. So far every cause for the ABS light to come on, even when it is intermittent, has been a sensor and every time a slight tap on the end of the sensor has corrected the fault.
The reader is part of the Nexus software and the convenience of having it tell me which specific sensor is the cause of the problem has made the purchase of the reader worth every penny.
I bought all my readers from ebay with DDEC specific software, and this last one had the bonus of having ABS software.
1999 XLV X-6872, liberty #440 -
Actually, my pro-driver dash readout indicates which wheel sensor is the culprit. Remember though, I have the 2000-2001 dash in my 1999 chassis.
I had my light on for a while and repositioned the left drive by hand (just pushed the wire in, I don’t have the diff mounted sensors) and the light went off. I do, however, get the light whenever I am doing tight manuevering causing extreme wheel speed differences. It goes off after a few miles of normal driving.
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