ABS and ATC lights on dash

[Bill R]

Was a little confused about the ATC light until I looked at @Georgia Mike manual versus my manual.  We have different model coaches but the same year.

It turns out that for my model the ATC dash light will go out a few seconds after engine start and will flash quickly only during an "ATC event".  However, in Mike's manual it says the light will be steady on and will flash quickly during an "ATC event".   Snowflakes!!

A misnomer I had was that the ATC was only active if I had the switch on.  But that is not the case, the ATC is always active, and if you are in a situation like icy conditions and you have drive wheel slippage "ATC Event" and flashing ATC light, you can engage the switch to prevent further slippage.  Once you are out of these conditions you should turn the switch off.

@96 EVO What I read in my and Mike's manual is you are not able to turn the ATC off on our coaches.

[jacwjames]

SNOWFLAKES😝

[96 EVO]

Bill, I would be shocked if they operated the ATC lamp to work the opposite on these coaches than other vehicles!

The ATC lamp on the dash is to remind you that you have switched automatic traction control off!

Having it off is sometimes helpful if your stuck, with one tire spinning. 

[Bill R]

@96 EVO  Ben - perhaps I have misapplied the terminology but not the purpose and function.   Can you explain further so I can understand better?  Below is what the manual says.  Are you saying that if the switch is applied the ATC is completely off or just reduced?   I really am trying to understand better what I think I understand.  If that make sense.

"ATC Switch: Activating the ATC switch reduces ECU control over engine torque. Momentarily pressing the ATC switch allows the ECU to increase the amount of engine torque applied to the drive wheel in an ATC event. The amount of engine torque applied to the drive wheel varies with the amount of drive wheel slip versus road speed. In an ATC event, the ECU remains active regardless of road speed or switch position. The indicator light flashes slowly when the ATC switch is activated."

[96 EVO]

Bill, even Google doesn't know what an 'ATC event' is 😀!

I've always said I think Monaco's manual writers were stoned all day!

Believe with ATC on (normal driving mode, no dash light on), if a drive wheel started slipping, ABS would stop that wheel from spinning.

ATC off, it would allow it to spin.

Edited December 17, 2023 by 96 EVO

[Bill R]

LOL - I think ATC Event is a Monaco term.  Here is another section from the manual.  ATC Event = ECU senses a speed differential in drive wheels.

"If a speed differential occurs in the drive wheel, the ECU enters Automatic Traction Control mode. During an ATC event, the ECU will automatically react to optimize traction and safety if the motorhome encounters a slippery road surface. Engine torque is normally reduced to limit drive wheel slip."

I think I got it now, at least for the moment.  🙂

 

[96 EVO]

Guess the only thing to remember is.... Stuck, not moving, try turning ATC off (dash lamp on).

Will it help.... maybe!

[Georgia Mike]

So it sounds like according to my manual that the light stays on all the time until an “event” happens. I agree it doesn’t make sense that they would make the ATC system in the same year act differently between models. I don’t know what to think now. I am getting ready to go on a trip next Sunday and I am going to try and see what happens with the atc light when I press the switch on and off to see if it blinks or goes out or something. I’m also going to make sure my abs light comes on momentarily when I turn the key on like Ivan suggested.

[cbr046]

11 hours ago, 96 EVO said:

I've always said I think Monaco's manual writers were stoned all day!

Only the Oregon ones. 

If ATC were engaged normally (no switch, no lamp) the rear wheels would bind or slip around slippery corners.  Not good.  But Monaco applies auto traction by slightly applying rear brake to the slipping side to get both wheels engaged.  Also not good going around corners in normal driving.  

I've read the manual thoroughly in the past.  It's confusing with it's double-speak.  This is what I came up with:  If in a slippery situation turn the ATC switch on (ATC lamp lights continuous).  If wheels begin to slip press and hold ATC switch down (ATC lamp starts blinking) until out of slippery situation. 

My 4-Runner is also in double-speak.  I wish they would just say "to engage posi-traction (or maximum traction) do this . . . ". 

- bob

[Georgia Mike]

I went over today to double check some things because it’s getting down to 24 here in Georgia tonight and the ABS light does come on for a few seconds then goes out so I assume the ABS system is functioning correctly. As I said previously if the ATC system was malfunctioning I would think the ABS system would be affected as well since they are using the same speed sensors. I have seen people talk about an abs board but not sure if there is an atc board. I looked in the wiring diagrams and couldn’t find anything on either system. I’m just thinking I might be chasing something that doesn’t need fixed but I’m just not sure.

[Frank McElroy]

On 12/18/2023 at 4:36 PM, Georgia Mike said:

I went over today to double check some things because it’s getting down to 24 here in Georgia tonight and the ABS light does come on for a few seconds then goes out so I assume the ABS system is functioning correctly. As I said previously if the ATC system was malfunctioning I would think the ABS system would be affected as well since they are using the same speed sensors. I have seen people talk about an abs board but not sure if there is an atc board. I looked in the wiring diagrams and couldn’t find anything on either system. I’m just thinking I might be chasing something that doesn’t need fixed but I’m just not sure.

The ATC system also factors in engine output power that its supposed to generate based on throttle position, RPM, road speed and gear selected. If the engine output power is below what the engine and transmission expect, the ATC light will come on and the system won't function even though all wheel speed sensors are working properly.  In this scenario, with the ATC light on, often is an early sign of plugging fuel filters.

[Georgia Mike]

On 12/20/2023 at 8:39 PM, Frank McElroy said:

In this scenario, with the ATC light on, often is an early sign of plugging fuel filters.

Thanks Frank but I eliminated filters from being the problem. I change all fuel filters every year no matter what including the one above the starter I can’t stand and get soaked with diesel fuel every time I do it. This ATC light has been on since I bought it and only goes out when I turn the key off. Toggling the ATC switch doesn’t do anything either that’s why I’m confused as to what the problem if any is. 

[Frank McElroy]

1 hour ago, Georgia Mike said:

Thanks Frank but I eliminated filters from being the problem. I change all fuel filters every year no matter what including the one above the starter I can’t stand and get soaked with diesel fuel every time I do it. This ATC light has been on since I bought it and only goes out when I turn the key off. Toggling the ATC switch doesn’t do anything either that’s why I’m confused as to what the problem if any is. 

Thanks for the additional info about the ATC light history and filter changes.  Based on this, my best advice is to read the fault code history with a shop that has the Bendix software to read fault codes on your ABS/ATC controller.  This codes reader plugs into the same rear port used to read engine diagnostic codes (not your front diagnostic port).

Although you could try the self diagnostic feature for the coach ABS system, it might not provide all the detailed diagnostics on the ATC system like a Bendix scan tool would.

[Scotty Hutto]

@Georgia Mike, I have the software and equipment to read the Bendix brake system fault codes.  Maybe next time I head south I can throw it in the truck and we can check your brake controller.  I’m in Marietta, so about an hour (or so) away. Let me know if you want to try and set that up.

Scotty

[Georgia Mike]

7 hours ago, Scotty Hutto said:

Let me know if you want to try and set that up.

Thanks Scotty, that would be great. I will PM you.

[Bill R]

@Georgia Mike  Mike I thought you determined from reading your manual (I read the same thing too in your manual) that for your coach the ATC light stays on continuously with key on.  If you hit the ATC momentary switch the light should slowly flash.   Does it do that?   If so the light is doing exactly as your manual explains.  If you believe the light should be off then the manual is wrong.  

[Georgia Mike]

18 hours ago, Bill R said:

Mike I thought you determined from reading your manual (I read the same thing too in your manual) that for your coach the ATC light stays on continuously with key on.

Bill, I know that’s what it says but I’m not 100% sure it’s correct. Every other year says the the light is off when driving plus when I switch on the ATC switch the light just remains steady. I’m not sure I left it on very long (maybe 10-15 seconds) so I might have to redo that test and leave it on longer. As I stated before my abs light seems to be working correctly although I have had it come on a few times while driving but when I get to the destination the next time I start it’s back to normal. The abs light always comes on for a few seconds at startup like I said previously so that is the normal abs test.