ABS and ETS lights on/ I found the problem/LONG

[jfreezn]

This was on my 98 ML320, other vehicles may be similar.

Since these lights would come on instantly, after starting the engine, I figured I had a hard failure somewhere in the ABS/ETS system. See my previous entry on this subject of a couple days ago.

After checking the 40 amp fuse that feeds this circuit, I pulled the relay, K25, that feeds the ABS high pressure pump. I can test a relay on my workbench and it tested fine. I also noted there are at least 3 identical relays so rotating them into the ABS socket was also an option.

I had a wiring diagram that I got from the Tempe library, which has a free Mitchell repair access. It shows a red wire going from the load side of the relay to the ABS high pressure pump motor and then to ground. Putting 12VDC directly to the load slot of the socket SHOULD have run the pump, but it didn't.

Testing further, I unplugged the two pin connector which feeds the ABS pump and put 12 VDC directly to the motor. By pulling the sheath back, I was able to see the wire colors. Since brown is always ground on Mercedes, I knew to put the plus 12 VDC to the other wire, to insure the rotation was correct.

The pump ran smoothly! I needed to verify that power was reaching the pump assy.

Unplugging the 15 pin connector from the ABS pump unit was a little tricky. The sheath over the plug pulls straight up and then the sheath becomes a ramping device that pushes the connector out of it's socket. My fingers could start the motion but it took a little pliers to get enough grip to release this connector. The bottom two pins were hot and ground and fed through the housing to the 2 pin connector. With my temporary 12 VDC still connected to the relay socket, I found that 12 VDC was indeed reaching the ABS pump assy, but NOT getting through to the 2 pin connector. The problem had to be in the ABS housing somewhere.

NOTE: At this point I found it conducive to remove the driver's side headlight unit for more working room. A 5 minute task to figure out how to release the plastic trim strip under the headlight where two nuts were hidden.

The front of the ABS pump unit appeared to have a wiring acces cover and I got really lucky here as the whole actuator control and wiring came off by removing 4 small 6 point screws. It just slid off the 12 pins that seal the fluid side of the magnet assemblies, No fluid is released and I had the printed circuit board in my hand.

Checking with my VOM connected to read resistance on pin 15 to the pin on the two pin connector that feeds the motor, I found high resistance with considerable fluctuation whenever the pins were flexed a little. BAD SOLDER JOINT! Where have we heard this before? The manufacturer is ATE, a well known vendor, but who knows how many ABS pumps hit the trash can because of a simple joint failure. At $1200 each, I am glad I took the time to find this problem.

The PC side of the board was covered with a 1/4" of clear jellied sealant, easily removed with an exacto type knife. I cleaned the old joints with brake cleaner, then I soldered both pins and in minutes the unit was reassembled and tested. Zero resistance is good! I used some clear silicone to close up over the newly resoldered joints.

Suffice to say that I rejoiced when the engine started and both lights were eztinguished. Knowing that I had ABS again was a big relief too.

I took a few pictures and will try to attach them. If this file is already too big I will send a separate file. Thanks to all who took the time to reply to my pevious note.

Jim in Phoenix

[ML320]

Great that you could fix it and thanks for the writeup, Jim. I poked around the ATE website and believe this is a picture of the MK20 used in your ML:

http://home.comcast.net/~anthoni6/MK20.jpg

[ML in OR]

I am sure you have had many responses to this thread. I too have a 98 ML320 that has had the ETS and ABS lights "stay on", and planned to look into your solution this weekend. Was wondering if you had input on how often this solution resolved the problem, or where there other solutions that worked as well? just curious. Aslo, I have not looked for the ABS pump on my car, Is it located near the drivers side headlamP?

[2M MACHINING]

Hi Jfreezn,
I to have suspected an electrical connection problem on my 2000 ML 320.
My question to you or anyone else with ABS unit is:
should the electric motor that is connected to ABS unit be running when engine is started.

Can someone with same vehicle check to see if motor is running by starting
engine and carefully placing your hand on electric motor to detect motor running or not.====PLEASE ONLY TRY THIS IF YOUR CONFIDENT AND WILL NOT CAUSE INJURY TO YOUR SELF.

Thank You

[DonB]

Wow, Jim, you really nailed this one; right down to the cold solder joint and intermittent behavior! I just finished fixing mine. It had the exact symptoms you talked about. Now it works great, thanks for the great instructions.

Don

[kwmccauley]

Seems I have the same issue with my 1998 ML320. I just replaced the $12 brake pedal switch tonight and that did not fix the problem. Will check out the bad solder joint possibility this weekend.
After you fixed the root cause did you have to do a reset procedure or did the start-up diagnostic automatic procedure detect no faults on its own?
Thanks for the heads up.
Ken

[DonB]

Sorry for the long delay. No, the lights went out immediately, without any help from me. As soon as I started the engine, the lights went out by themselves.

[acapulco36]

Found your info interesting. Yesterday my ETS light came on and has stayed on. I DO NOT have a ABS light on. Wondering if this could be related to a
similar soldering issue, or since I have only the ETS matter would you think
this may be a totally different matter ??

Thanks

[DocGeorge]

You got it right on, Jim. I think this is a common problem. I followed your directions and could not get two of the four 4mm bolts out of the assembly, no matter how hard I tried. I managed to get the cover off (but almost all of the clips broke off), and dig out the jelled sealant so I could check for continuity with the bottom plug of the two pronged plug. The continuity was okay, but I couldn't manage to test if flexing it made a difference, but the bottom pin in the unit (the one that connects to the brown wire) did seem loose to the touch, (this can easily be tested without removing everything first). Anyway, I started the car to see if the problem was still there, and the ABS and ETS lights didn't light up!

If anyone else tries to get the little 4mm bolts out, be careful, as you can't get good leverage, and it's very easy to strip the heads. Make sure you have maximum pressure against the bolt before trying to turn it!

At least it's working for now (at least til I hit a bump at some point), but now I know exactly where the fault is, and know what to tell the mechanic if necessary. (Perhaps putting a little silicone in the plug might stabilize it enough to maintain contact if it recurs?)

[kwmccauley]

I sent the ABS control module out to Module Master in Idaho. They did a quick turnaround on the rebuild and guaranteed the work. However, as this did not fix my root cause I did some further investigation after removing the ABS control module and hydraulic pump assembly. It turns out there was a chafed wire which was consistent with the fault code. Instead of a $1,600 part and $600 labor (dealer repair prices quoted), it cost me about $0.10 worth of solder and probably a buck for shrink tube w/ sealant to waterproof the repaired wire splice.
This was on a 1998 ML320 with about 190k miles.
Ken

[jfreezn]

Originally Posted by kwmccauley

I sent the ABS control module out to Module Master in Idaho. They did a quick turnaround on the rebuild and guaranteed the work. However, as this did not fix my root cause I did some further investigation after removing the ABS control module and hydraulic pump assembly. It turns out there was a chafed wire which was consistent with the fault code. Instead of a $1,600 part and $600 labor (dealer repair prices quoted), it cost me about $0.10 worth of solder and probably a buck for shrink tube w/ sealant to waterproof the repaired wire splice.
This was on a 1998 ML320 with about 190k miles.
Ken

Ken,

I was very surprised today, when I logged on to the forum, that my ABS/ETS thread was active again after 20 months. I should mention that I have had absolutely no ABS problems since the cold solder joints were repaired.

you mentioned a chafed wire and I am sure many of us would like to know if it was on the 2 pin connector or the 15 pin connector run. We could take steps to tie the cable more securely if you would care to reveal where it needs attention.

Thanks,

Jim in Phoenix

[kwmccauley]

Jim,
Good point and happy to oblige. The chafed wire was in the harness that runs behind the driver's side headlight and feeds the 15 pin connector that plugs into the back of the ABS control module/hydraulic pump assembly. It was the wire that feeds Pin #13 in the connector block but it could have been any of them. After doing the splice repair and weatherproofing, I also wrapped the harness in new friction tape to preclude further abrasion of the wire insulation. No problems since doing the fix in early January '08.
Ken

[jfreezn]

Thanks, I'll check mine out in the morning

Jim in Phoenix, 98 ML320, 155,000 miles

[GizmoSA]

Originally Posted by kwmccauley

Jim,
Good point and happy to oblige. The chafed wire was in the harness that runs behind the driver's side headlight and feeds the 15 pin connector that plugs into the back of the ABS control module/hydraulic pump assembly. It was the wire that feeds Pin #13 in the connector block but it could have been any of them. After doing the splice repair and weatherproofing, I also wrapped the harness in new friction tape to preclude further abrasion of the wire insulation. No problems since doing the fix in early January '08.
Ken

Can anyone tell me if this is left or right hand drive?

[kwmccauley]

As I am a resident of the United States, the work described in all of my posts was done on left hand drive vehicles. I was not a member of this forum when I had the pleasure of living in countries with right hand drive vehicles.
Ken