BAS ESP and ABS MIL Issue

[msmith66]

Hello all. 1998 SL500 having a problem with the BAS/ESP and ABS lamps coming on at the same time. Funny thing is that they only come on after the car has been operated at highway speeds for about 20 minutes. The lamps reset after turning off the engine and won't come back on during around town driving - only on the interstate after 20 minutes.

Some information on benzworld has indicated a low voltage fault but my system seems to run pretty stable at 13.5v.

Any ideas? A faulty wheel sensor? Vacuum problem?

[G-Benz]

You need to pull codes to verify, but typically, it's a faulty brake switch.

The same issue cropped up on my 01 CLK and a 99 ML320 I formerly owned...the switch replacement corrected the problem.

[msmith66]

Thanks G-Benz. I thought I did a pretty thorough search and didn't turn up anything but have since found more than a few discussions of this topic and they all point to the same thing.

[msmith66]

Just an update - I have been in the UK since January and returned recently. I replaced and adjusted the stop lamp switch per the shop manual but still have the same problem.

I still don't have the codes. I am looking into getting a car soft system to read them. I believe a general fault in the ABS system is causing all three systems to go offline.

[mbdoc]

Yes, any of the MANY sensors on that system can cause all 3 lights to come on at the same time. In your case most likely a speed sensor input.

Having the codes read will help with diagnosis.