W201 ABS light

[Andras]

Dear Community,

we have a MB 190 (W201) in the family for 30 years now. It is in very good shape, except for one thing; the ABS light keeps turning on.
The symptoms are: the ABS light turns on when we leave the driveway (so not while stationary). The ABS does not function at that time. This usually happens when in the winter (yes, the issue persists for years, but not even MB dealership knew how to fix it). It turns on occasionally during summer as well. When the ABS light is off, the system works.
What we tried to do:
- re-solder the overload protection relay
- replace the overload protection relay with new (aftermarket) part
- clean the wheel and rear sensors, and the "sprockets" in the wheel

Any tips how to go about fixing the issue?

 

[KennyN]

What does a diagnostic test show regarding the fault ?

Seems a bit strange that you headed straight for an overload protection relay when the issue maybe with a wheel sensor , even if it is clean.

K

 

[Andras]

I do not have that old tool to read the codes. The relay was recommended to others with similar issues as a common problem, which is why it was addressed.

 

[mattkh]

Check the brake lght switch.

 

[Andras]

Check the brake lght switch.

the brake lights work fine

 

[Uncle Benz]

There is also a relay on the ABS unit itself that sometimes plays up. You’ll need to remove the single screw on the black cover and lift it off. The relay is underneath the cover. Used to change a few back in the day, but these are becoming rare cars now.
Thinking about it, there are two relays under that cover. Only one used to give trouble. One is silver, one is black. Don’t quote me, but I think it’s the silver one that used to be troublesome

 

[Andras]

thank you, I will check it. Any way to test it or just go right ahead and get a replacement?

 

[ajlsl600]

Dear Community,

we have a MB 190 (W201) in the family for 30 years now. It is in very good shape, except for one thing; the ABS light keeps turning on.
The symptoms are: the ABS light turns on when we leave the driveway (so not while stationary). The ABS does not function at that time. This usually happens when in the winter (yes, the issue persists for years, but not even MB dealership knew how to fix it). It turns on occasionally during summer as well. When the ABS light is off, the system works.
What we tried to do:
- re-solder the overload protection relay
- replace the overload protection relay with new (aftermarket) part
- clean the wheel and rear sensors, and the "sprockets" in the wheel

Any tips how to go about fixing the issue?

My best hunch. Wheel speed sensor, reluctor ring and or rodent tryin to f up ur day?

 

[Andras]

My best hunch. Wheel speed sensor, reluctor ring and or rodent tryin to f up ur day?

Rodents are not the issue, luckilty. The reluctor ring seems undamaged. The sensors may be the issue, but why would they only fail when it is cold outside?

 

[mattkh]

...., but why would they only fail when it is cold outside?

Temperature affects the resistance of a copper coil.

 

[ajlsl600]

As above prob more if already failing I had to change one recently cud see nuthin wrong with it cheapest bidder produced and basically designed to fail never issue in 20 Yr w208 I suspect QC has changed a lot since 2001!!!

 

[brandwooddixon]

the brake lights work fine

The brake light switch was possibly mentioned as on some cars the switch also has a CAN bus speed signal passing through a second set of contacts. I know that this is the case on the W210 and was used to disable the cruise control. As the CAN bus signal is particularly sensitive to signal interruption caused by poor contact, the cruise control would drop out and yet the brake lights would still work (the cruise drop out being triggered by a break contact whereas the brake lights are triggered by a make contact).

 

[MBW201]

This happens when you have bad cables to the sensor, most common is in the bend where its on the clip strut. Try change distributor cap, some of the cheapest one from china make this error due to terrible isolation.