There are so many possible causes when you have ABS problems that it makes tracking it down a little difficult. When mine acted up I didn't want to give a dealer or my regular shop a blank check to fix it. I was afraid they might end up throwing in a bunch of expensive parts like the pump and control unit as they attempted to get it working.

There should be a way to jumper the pump to see if it does run but I don't know the procedure to do that. Let us know what the final fix is.

Yesterday I tried replacing the removable 4-pin relay on the K40. That did not help.

Today, I unplugged and re-seated the connectors on the K40. I also removed the bottom cover and inspected the circuit board - no visible problems. There are some components on the other side of the board. It seems there is more to the K-40 than just the relay, fuses and sockets.

I replaced the 4-pin relay at the back of the driver side fuse box.

Have not given car a real test yet. Over the past month, the symptoms have been very repeatable.

- No problem with first start of the day.
- No problem if car is let sit for say 4 hours or more.
- If car is restarted soon after, for example, a 1/2 hr trip and 1/2hr stop, the ASR/ABS/BAS warning lights all come on. Usually this happens as car is started or just after. Never during trip. Except once when I simulated an emergency stop with ABS in action.

We will see what happens today!

OK - No improvement. Running out of things to try (:

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Wanted to post a resolution that worked when my '01 E430 Sport died suddenly without warning.
I have access to STAR C4 diagnostics, which gave me two F (currently failed) faults.
They were ESP with part # 0295456332 and ICM (Instrument Cluster) / # 2105401811

The ESP part is a control module location under cover passenger side by firewall, along with 4 other modules.

My first attempt at repair was replacing the brake light switch because I had over two dozen F codes first DX.
and had this problem before on a '02 E320
I used a NAPA part by ECHLIN, as the Stealership was not open and it was Friday PM just before holiday weekend.
Normally would not advise anyone to use aftermarket Brake Light Switch as many have and regretted it.

In any case after putting in the new BLS and rescanning I was able to erase all fault codes excepting the ESP and ICM. Found the ESP module on eBay cheap so ordered it ($20).

Meanwhile I was researching the issue online and found many models of Mercedes having problems with the K40 fuse box and some fixing it by resoldering circuit board. I assumed if my box was faulty STAR would tell me so!!!!!!
but alas that was not to be the case. Do to the experiences of many other Mercedes owners, I also bought a K40 board from eBay with connectors cheap.

One prominent list contributor suggested unplugging the ABS module at the pump and this allowed me to get the car started once I replaced a 10A fuse in the K40 box, that would blow if the ABS module was connected!

Received both modules today and Problem Solved! It was the K40 fuse box not the module STAR faulted! Firsted installed the relay from this box, no dice. Then I unplugged the ~ 10 connectors and installed the new K40 box, plugged everything back in and Viola, no ABS, ESP, BAS lights! I had removed it a few days back to inspect the circuit board for any sign of de-soldering or brown shorts. Could not see anything but clearly that is what happened.

There are a few Youtube showing DIY re-soldering the K40 board and having it work. Interesting that the STAR diagnostics pointed me to the control unit and not the K40 box!! Hint may have been the blown 10A fuse I found in the K40 box. I hope this information helps others when the Brake light switch is either not at fault or its replacement does not solve the problem! Turned out to be a cheap fix.

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