ABS and ETS lights on/ I found the problem/LONG - Page 5 - PeachParts Mercedes-Benz Forum

Yemi Olukomo · #61 10-18-2016, 06:54 PM

Hello,

Finally my ML320 works fine without any yellow lights for over a week now. Thanks to the ideas from Jim and other guys on this forum. Your submissions lead me to the problem area but my actual solution is a little different from all yours. It may help someone someday. Here is what I did:-[*]Step by step troubleshooting:
- I hardwirer the two wires to the ABS pump. Pump works fine.
- K25 relay was switch with the fan blower relay. K25 works fine.
- F22 and F27 fuses are ok. I cleaned the legs with a wire brush and replaced them.
- During panic stop on the road, K25 contacts will close and send 12v to the red wire to the ABS pump. So, if K25 is okay, I assume that the ABS electronics control module is bad. Some of you guys complained about weak soldering joints on the electronic board. Removing the 15pins connector is a little hard with bear hands. After pulling up the latch/cover on the connector, I had to use the rod of the spanner to lift it up. Then, the cable got released. 4 long screws hold the ABS electronics board to the ABS module.
- I scraped off the gel-like coating on the back of the ABS electronics board. After wire brushing the contacts clean, I re-soldered all the joints....taking care that no two joints touch each other.
- After clean soldering, I applied White Silicone gel to cover the electronics side and cover.
-Up till that time, I assumed that my problem should be solved like others who had weak soldering joints and re-soldering solved theirs.
Lo and behold, excitedly I returned the board to the car, screwed it back and attempted to connect the two wire connector from the ABS pump. That is my real problem. The installation of the wires (especially the red) were just peeling off. The conductor has been seriously oxidized and had changed colour. In fact, both wires just came out of the connector. I took some pictures. Hope there is a way to upload them. I bought the vehicle from USA with the ABS & ETS lights on. After driving for about two months, the intermittent brake light issue started and I had to restart the vehicle several times a day!!! Very annoying and already cost me a new battery. I live in a very muddy area and water must have been finding way into the ABS Assembly thus oxidizing the ABS pump cable and making it loose firm contacts with the ABS electronic board. Hence, the reason for the electrical fault that intermittently switch on the emergency brake light and which will disappear after restarting the vehicle. This type of problem is always more difficult to solve.
-Now, I had to remove the ABS pump completely. After sliding out the plastic cover, one long screw holds down the ABS pump. Pump came out nicely and I took back to my work bench to work on the cables.
- I reinforced both cables by soldering them all the way from the bottom to top. Then, I re-insulated each with black insulation tape. To prevent water from entering the joints, I pushed some white silicone gel into the base of the wire where they enter the pump assembly. The whole surgery looks successful. Slided back the plastic cover and reconnected the all the cables.
- To have enough room to work, I had to remove the mud cover on top of the tire and also the driver side headlamp.
-Returned all connectors and also added more white silicon gel to seal off water ingress into the ABS wire connector.
- Moment of truth came when I started the vehicle and all yellow lights disappeared immediately. No need to erase any fault with a scanning tool. The whole system just reset itself. Hurray........I jump up for joy because none of all the mechanics I have visited could even solve the problem. Most were doing try and error methods. Be careful for some mechanics, they will only disbale the lights on board but the problems will remain.
- For almost 2weeks, I have been driving with a clean dashboard.
Regards to all,
Yemi from Nigeria.

Quote:

Originally Posted by 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