Community Forums

PatColau · 10-27-2010, 12:33 PM

I have had intermittent ABS warning lights for the last year, and have looked at the forum to try to figure out what is wrong. So far, no luck in finding either the ABS ECU or the blink code switch. By the passenger firewall I have located the ABS,Engine & transmission diagnostics ports, and have tried switching the toggle switch on the right to "ON", but all that does is sound a warning alarm from the dash panel.
I have downloaded the Meritor maintenance manual from the ACA website and was hopeful that I could use the blink codes to diagnose the problem, but I can't find the blink code switch that I am supposed to press for one second. Does anyone with a 2001 model know the location of the switch and the ECU?

Dave & Colleen · 10-27-2010, 09:10 PM

You may not have blink code switch depending of the ABS unit revision. My 1999 has a version “C” ECU meaning, that it doesn’t have a light. You will need to get the Meritor Wabco maintenance manual no 28 revised 4-98. In order to get a blink code you jumper 2 pins on the testing plug which in turn will utilize the dash indicator light as the blinker. Its best to have a 2nd set of eyes to compare what you thought you saw/wrote down then follow the blink code tables. I will locate the pin #’s later this wkend. Or, call Meritor help line with your serial # of your unit. Because the ABS black box is very very expensive the 1 st worry is that jumper’g will burn it up. It won’t and didn’t on mine. Plus, the system version C’s have a fail safe mode that will reset the error once its fixed so re calibrating the whole unit via PC program is Not necessary. I fact the PC program unit will not work with “C”.

PatColau · 10-28-2010, 04:32 AM

Dave, thanks for your insight, this is very helpful. In addition to updating me on which pins to jump, could you tell me where your ABS black box is located? I can't find mine, and obviously need to to find the serial number. I took my unit into a local shop, who are usually pretty good, but they couldn't locate the box either.

Algoma · 10-28-2010, 11:15 AM

I thought the "C" model was only on the '98 and '99 models. Anyway mine is located on the firewall to the left of the steering wheel close to the floor. It is hidden in the corner and may be difficult to get at. I had to cut away some of the box that holds the gear selector. You will probably find the Allison ECU there too. A new ECU is about $1300 but there are places that will repair them. I gave up trying to fix mine and removed the ABS indicator bulb. Brakes work fine without it.
The "C" model is "in-cab" but later models could be mounted outside, in which case yours could be located near the master cylinder under the driver's floor.

PatColau · 10-28-2010, 03:52 PM

Thanks John, i will look in the places you indicate & let you know if I find it.

PatColau · 10-29-2010, 07:25 AM

I have had no luck finding the ABS black box, it doesn't seem to be on the firewall near the drivers side, nor underneath the drivers floor. I found the transmission ECU on the passenger side next to the room slide assembly door.
I looked inside the generator slide openings, no luck!

TedG · 10-29-2010, 08:59 AM

I have a 2001 40FDS. The ABS black box is located under the dash, just above the steering column. Difficult to get at, but accessible easier if you remove the drivers seat. My blink switch is located behind the access panel in front of the passenger seat.

PatColau · 10-30-2010, 05:02 AM

Thanks Ted, I will look there. By the way, is your blink switch a toggle switch located on a panel where the Engine ,Transmission & ABS diagnostic ports are located? The panel I'm talking about is in the same location you mention in front of the passenger seat. If so, do you switch the toggle switch on for one second, then turn it off to read the codes?

PatColau · 10-30-2010, 10:10 AM

I have found the ECU for the aBS, and it is indeed a D version on the 2001 36MDDS. It is located (on my coach at least) on the front firewall to the left almost against the sidewall of the coach on the drivers side behind the steering wheel assembly. It could not be more remote.
I will have to call Wabco & ask them what it means when the blink code doesn't blink.

TedG · 10-31-2010, 10:57 AM

Yes, my switch is located in the same place. One more thing, my switch was also defective the first time I tried it. Mechanically it was broken internally which I confirmed with an ohmeter. I also repaired several loose connections in that area....very sloppy work using wrong size terminal lugs, improper crimping, etc. You should get blink codes as soon as you turn the ignition switch to on.

I took my motorhome into a truck repair shop that was recommended by Wabco. THey could not find anything using the diagnostics and thought it is a wiring problem. They were really not interested in any further troubleshooting, or working on a motorhome.