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W210, W211, W163
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Discussion Starter #1
I have been searching this forum for many hours and tried several tips on my 2000 ML320 101k miles. I keep getting the ABS/ETS/BAS lights come on randomly. Well, I could drive for a while and they may not come on or come on a few seconds after a start. It seems that they are more related to the outside temperature, because it is a sure thing they come on when it is very hot outside (and humid, its MD).
Now I have tried a few things but still get these lights coming on.
The things I have tried so far are:
1. New brake switch from the MB dealer.
2. exchange the battery with my E320 which is much newer.
3. exchanged the K25 relay several times with other ones in the fuse box.

So far, I still get the lights coming on. I have a Carsoft and scanned the codes and I get code:
C1401 High Pressure Return Pump Circuit Open/Shorted; Will Not Shut Off

Oh, I also jumped relay K25 contacts and made the ABS pump motor manually turn on, and it worked.

Any ideas what could be the problem? I am running out of ideas. Well, I am thinking to open up the ABS module and check the connections there make sure they are ok, as that also seems a common problem. Could it be that?

Any suggestions are greatly appreciated.
 

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Discussion Starter #2
Any suggestions?

Any one has any suggestions? I know there are some very knowledgeable members in this forum. Can someone please give some advice?


Btw, I noticed that actually when the car warms up completely, engine quite hot, 100 C, is when I get the lights to come on right away. When the car is cold it doesn't do it until it warms up.
I am wondering if the heat in the engine compartment is causing the ABS module/pump to malfunction.
 

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Super Moderator
99 ML430, 00 ML320, 05 E500 4matic Wagon
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22,475 Posts
Wow, even in 100 degree heat ours never ran hooter than 90º C even in Chicago stop
and go highway traffic with the AC on and 5 people on board. With that high a running
temp I am wondering some sort of vapor lock problem is going on.

What is the history of fuel delivery maintenance? Fuel pump and especially the diabolical W163 fuel filter?
 

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'08 ML320 CDI
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884 Posts
I think that's the same light that randomly used to come on on ours as well. It's the light on the left, right? Mine usually came on doing slow maneuvers doing a u-turn or driving in a parking lot. After we replaced the brakes, it magically disappeared. No idea why but I'm guessing it was related to some sort of sensor in the wheel/brake area?
 

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Discussion Starter #5
On mine are all three lights to the left. BAS/ESP/ABS I wonder if it is the terminal contact inside the ABS module that are bad? But it seems that it is more related to the high temperature on my engine bay than anything else.
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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7,035 Posts
Do you reset the steering angle sensor (procedure in the owner's manaul) when you pulled the battery/disconnect and brake switch job ?

I am just trying to be helpful here, no jab intended, it's a common oversight with others...
 

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Discussion Starter #8
I did do the reset of the steering angle sensor when replaced the battery. Now I have the ABS module/pump pulled apart but everything seems fine.

Other people in the past that have had this problem seem to have solved it by replacing the ABS pump, bad battery, or a bad wheel sensor.
I will keep working on this.
 

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Discussion Starter #9
Back to report everyone.

First, I would like to thank everyone for their replies.

Second, I have found the problem.

As I described before the lights will come one randomly and seemed to be more related with temperature. Well in a way it was.

So I waited for the lights to come up, car warm, and then tried to manually get the ABS motor to run again by jumping the wires on relay K25. Now when the car is cold, I could hear the motor run, but this time, the car had run for 20 min, and the lights had come ON. Well, when I tried the ABS did not run this time. Once the car cooled down it started to run again. I checked the resitence at the ABS pump connector and everything was fine there.

My conclusion was that the ABS motor was acting up after it runs a few times. So I decided to pull apart the ABS motor and sure enough the brushes are almost gone.

It seems that since they were making very little contact, they would work fine when cold, but once the motor is turned a few times then they quit.

Now, I have a bad ABS pump. Since I don't want to spend $250 to rebuild it, I did some search online and found the perfect brush for the motor.

The brush that fits the motor should be 5mm by 5 mm and around 13 mm long. I found the right brush on a website called Carbonbrush out of California. The part number L5-5H and it should be material "Copper M" on their website. For only $15 and some patience I will have my ABS motor rebuilt.

And here are a few pictures to show the actual problem.





I don't know if there is a DIY on the ABS motor, but I think since this motor is so problematic on the ML there should be one.

Thanks again, and hope this helps someone.
 

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Merc ML270 CDI '01 & Merc Vito 108D '99
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113 Posts
I think i have this problem, but lights 99% are on as soon as i drive away, seems to stay off for longer in very wet weather, im wondering should i look into the pump or a wheel sensor, altho i also have a "high pressure in circuit" fault in it????
 

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Discussion Starter #12
When the brushes shown in the picture are completely gone, then you will get the three ETS ABS and ESP lights come on all the time.

Previously I had another ML320 and the three lights where coming as soon as I would start to drive off (within 5 seconds after I started to drive). That was easier to diagnose and had the same problem. The ABS motor was gone, brushes 100% gone.

This one was harder to find the problem since the brushes were "almost" gone, they were making minimal contact and thus will work ok sometimes usually when car was cold.

If I was you, and if I have this problem ever again, the first thing I would check is the ABS motor located right under the windshield washer fluid tank.

Take the washer fluid tank out. The ABS motor has only two screws that hold it in place. Take those off and pull it out. Test it by suppling 12V to it. Or even better pull the shaft out to check the brushes. As shown in the picture in my previous post. Mine would spin fine when the motor is cold, but after it warms up then it stops working thus my lights coming on.

I am waiting for the brushes to come so I can put everything back together. I will try to take a few pictures when I do that.

Good luck.
 

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Merc ML270 CDI '01 & Merc Vito 108D '99
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And when you say " The ABS motor was gone, brushes 100% gone", was this just a matter of replacing the bushings??

I'd like to check out my bushings as i have some spare time today, you say removing the pump is easy, do i have to bleed the system after or can i just remove the pump on its own??
 

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Discussion Starter #14
Most likely you wont have to bleed anything.

If you look at the pump that I am holding on my hand on the pictures, you will see the end of the shaft and a bearing on it. On the end of that shaft, there is a small cap, which is not shown in the picture because it stays inside the ABS unit. But if that cup comes out when you pull the pump out, then you will need to bleed the system after you put the cup back on.

Now the cup doesn't usually come out that easily but it is possible. When I usually pull the pump out, as soon as i remove the screws I pull the pump out very little. Just enough gap to be able to insert a flat screwdriver toward the shaft you see on the picture to ensure the cup doesn't come out. This may sound complicated but if you pull the pump out once you will see it is very easy.

I would just remove the screws and pull the pump out, if the screwdriver tip doesn't make sense. Just keep in mind there is a 5% chance that cup will come out and then you will have to do bleeding.
 

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Merc ML270 CDI '01 & Merc Vito 108D '99
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ok, got it out, do these bushings appear to be worn??

 

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Merc ML270 CDI '01 & Merc Vito 108D '99
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a more detailed photo

 

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Discussion Starter #17
No. Yours seem to have some life left. Just to double check put 12V to the motor contacts, or with a Multimeter check for continuity (resistance). But it seems that your problem is not the motor itself.

It wasn't that bad to pull out was it?


This is the next thing I would check. Once you double check the motor, then put it back. Pull out the cable that goes to the ABS unit. Get a multimeter, test the resistance on the two bottom pins on the ABS unit. The two bottom ones are the ones that take power to the motor. And it seems that several member on the forum have had contacts that were loose. In case there is no current going through the two bottom contacts then your problem would be that part right there (the opposite side of the ABS motor you removed). You will have to pull out that part, open it up and solder the contacts on the back. I didn't have that problem but it is common as well. There is some instructions on this forum about that as well.

Good luck.
 

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Discussion Starter #19
I am glad it was helpful. I have put about 2000 miles and the lights have not come back. I think we are good for another 100k miles.
 

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Merc ML270 CDI '01 & Merc Vito 108D '99
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did your bushings look like mine?
 
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