Last weekend I thought I fixed my problem by replacing the K40 relay. Originally on my 2001 E55 the ABS, BAS and ESP lights all came on when I started the car and it said "Visit Workshop". The ABS pump was running constantly and continued to run after turning the car off. We had to unhook the connection to the solenoid pack that connects to the ABS pump to stop the unit from running.

After the K40 relay replacement the car performed perfectly for about three days. Yesterday, the lights returned and the ABS pump continued to run as in the past. I unhooked the connection to the solenoid pack again.

Is it possible that I got a defective K40 relay or could there be some other problem that causes the K40 relay to go bad? The relay was a genuine Mercedes part. Since the ABS pump continues to run even with the key off and removed, the K40 relay seems to be the cause.

Here is the first thread:

ABS, BAS, ESP lights on

I would check the K40 you installed. I replaced mine in April and the one I got was defective. Since I replaced it myself, I had to have the dealer see in person that it wasnt working. We just swapped it out in the service lane. The replacement one had bad contact, if you pressed on the top while key was on you could hear the relays clicking.

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Dennis
2006 E320 CDI Black/Black Leather. Nav, HTD Seats HK stereo 32000 miles.
2000 VW Passat 1.8t 300,000 miles as of Dec 09, 2009 original owner
1997 E300d Silver 300,000 miles As of Jan 05, 2010
3rd owner SOLD

e300D97:

Was your relay defective immediately or did it work for a few days?

I suspect that my relay is defective but since it fixed the problem for three or four days, I'd like to be certain there isn't something else causing the relay to go bad. Does anyone know if there is anything in the ABS system that could be defective and would ruin the relay after a few days?