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