ABS and ATC Lights On?

[Robin_M]

Both the ABS and ATC warning lights came on in our 2007 Monaco Diplomat, and won't go out. Cannot turn on ATC at the switches. Brakes seem to work normally. Not 100% sure, but I seem to remember, from a few years back, that these lights can come on and it doesn't necessarily mean that the systems are bad. But I cannot remember the details. Can someone please refresh my memory about why this might happen, and what I might do about it (other than take the rig to a mechanic)?

Thanks.

[RustyTools]

It's the same circuitry that indicates when the holding tanks are full or the ashtrays need cleaning. And those mean you need to buy a new rig. (sorry, just waiting for dinner to finish getting cooked).

I had the same problem driving in the rain, and one of the mechanics at the old Monaco Wildwood FL Service Center (now Alliance RV) told me it was because there's a connector common to all Monaco brake-wiring harnesses for the tag-axle. Since we don't have the tag, he said the connector just sits there and gets dirty and often shorts out. He crawled under the coach and said he was going to tape over the connector. Not exactly sure what he did, or where the connector was (I suppose at/behind the rear axle) but my '06 Endeavor hasn't done it since.

I'm kinda foggy on the exact details too (several years ago as well) but I hope this helps.

[jacwjames]

Your braking system will work but the Antilock Braking System isn't working. You can drive your rig without a problem.

I have an older rig, 2002 Windsor, and periodically have had problems with the ABS light coming on. My ABS control module is located in the front drivers side electrical bay under the driver side window. It is located in the lower left corner mounted on the side. Unfortunately it is prone to moisture and dirt.

There should be a section in your owners manual on the ABS system and how to recover codes. Here is an Eaton Manual that has the codes and explains the system
http://www.heavydutypowertrain.com/md200codes.pdf

Yours may be different due age.

In my case I turn on the key, wait for ~5 seconds, press the brake pedal, and then go outside and press the small button on the control module. There is a LED light that give blink codes, normally it is a 2 number blink. The last time I had a problem it showed it was a bad wheel sensor, front driver side. In the front you can actually pull the sensor out, I cleaned it and put it back in. Seemed to cured the problem.

In the past I've also had an issue with dirt getting in the small button on the module. I've taken the whole module out but unplugging 2 wiring harnesses and loosening the 4 screws. I then used compressed air to blow the whole thing out and rapidly pressed the button to dislodge dirt etc.

I've also read that a bad ground will cause the module to go haywire, the last time I had it out I ran a new ground wire from the chassis and an made sure the module was grounded.

My last trip was ~3600 miles and the ABS light stayed off essentially the entire trip. It will still come on momentarily if I hit a hard bump.

[Robin_M]

Thanks, Rusty. That may well be our problem too. At least it's a very good thing to check.

[stuhly]

Another cure is to take the bulb out of the warning lite. Doesn't fix anything other than the lite irritating you.

[Robin_M]

Thanks, Jim J. That's ANOTHER good thing to check for.

[nodine]

Originally Posted by Robin_M

Thanks, Jim J. That's ANOTHER good thing to check for.

Robin,

Don't forget to check the probes at each wheel. There is a tone ring on each wheel that is adjustable. I don't remember the procedure but others may chime in. If the gap between the tone ring and the sensor is to wide the ABS light will come on. There have been cases where these sensors have worked loose.

Here is some light reading for your pleasure:


Bob

[Robin_M]

Originally Posted by nodine

Robin,

Don't forget to check the probes at each wheel...
Here is some light reading for your pleasure:

Bob

Light reading? -not so much, but certainly informative, interesting, and apropos. Thanks much, Bob for your helpful input.

[jacwjames]

One thing to consider is trying to clear all the codes out of the memory, there is a specific sequence that you have to use to do this. In my case, since my ABS module is in my front drivers side run bay I had to have my wife help as you have to hold the brake pedal down while you hold the test button down at the same time.

Also, you have to be careful when trying to read codes. If you hold the button down too long it will put the ABS system in a mode that the light stays on all the time. I now only hold the button down for a count of "one one thousand".

[YC1]

My 08 had the warning coming on and it seemed to always be the same bump in the road. Following the wires from each sensor I found some connectors that were a bit corroded. Cleaned and reattached the error still came on. The rear sensors are not accessible on mine without removing the wheels so I just checked the front. The front ones are just slid in under friction. They have a bit of a set of ears. Hard to describe but a pair of pliars and some careful turning and pulling had them out easily. I found a large gob of grease on the left front one. How it got there is a mystery but after cleaning the front sensors I have not had any issues in many years.

[Robin_M]

First, thanks to all who have responded.

What we've seen here is that there are several reasons these warning lights can come on mostly having to do with dirty wheel sensors or fowled contacts in the wire harness. Obviously, that is going to cause the ATC system not to work properly, or more likely, not to work at all until the problem is resolved.

But here is an interesting question… When this happens is the ABS functionality of the brakes also disabled, or does that system, without the ATC sub-system, continue to function normally?

[YC1]

I forgot about a write up made many years ago. I have not edited it so you will need to read the full report.

I have an 08 Endeavor and it has acted up on occasion too. This is a common issue but on a recent trip mine came on and stayed on. Shutting the engine off and on did not help as in the past. Lots of folks mention cleaning the sensors but there is no way to clean the ones on my mh. The following information is copied from previous threads and I keep a copy to quote from.

"In the front run bay, there is a relay with a reset button specifically for the purposes of resetting it--somehow--check owner's manual or call Monaco tech support...I bet with all the disconnecting you did, you might have thrown the relay for a loop.
__________________

Also try turning off batteries. You might need to drive over 5 mph to get them to reset."

My front run bay does not have a reset button. I actually looked for one yesterday and did not find one. Turning off the batteries might clear it for awhile.

Here is how I think I resolved mine. I am an ET with 40 yrs in the vehicle electronics installation business. Not abs or such but radios etc. Cop car build ups and fire trucks so some excellent experience.

Mine too was intermittent and weather sometimes seemed to be the cause but a particular bump I go over seemed to trigger it on more than one occasion. Once the light is on the cruise control does not lock on my unit.

As I was trying to figure out how to remove the sensors I discovered they have a long pigtail going to a plug. Research showed me that they should have about 1700 ohms resistance. Following the wire to the plug the first one over the rear axel showed signs of water corrosion on the pins. I cleaned all four sensors and checked their resistance. Using some WD 40 on each connector before reconnecting them should help keep the water out. I only found one that was really suspect and a second that showed only slight signs of water. Since doing this I have not had an issue. We just took a 300 mile trip and it worked perfectly. I am confident this solved my problem.

Except they came on again on a shorter trip after hitting that special bump on hwy 20.

--------------------------------------------------------------------------------------------------------------------------------

For a long time I was afraid to pull the front sensors out because they seemed very very tight. I finally gave one a twist and it moved. It came out without much effort after that. It was very greasy and had a large clump of grease and grime on the end of the left front one. The lump was about 1/8 inch thick. This definitely could be the issue. After cleaning them I test drove a short distance and no issues. The sensors do not go in as far as you might think. There is quite a bit still sticking out once inserted. There is a copper/brass looking insert the sensor sits in. Mine seemed to be in pretty good shape but that clump of grease on the one was significant.


The rear ones seem to be accessible only by pulling the wheels so they were never removed for cleaning.

It has been over 6 years and no more problems.