I have a '90 w124 300D. It comes with ABS but no other form of traction control. I had some small (I hope) problems with my ABS warning light & posted some questions. I learned that the system in my car has wheel rotation sensors for the left and right front wheels and a third sensor in the differential.

I think I know how ABS works, the rate of rotation of each wheel is compared and then brakes are selectively applied. Since my unit only uses three (3) sensors does that mean that brakes on both rear wheels are applied simultaneously or can that single differential sensor somehow determine that different braking should be applied to the separate rear tires?

Thanks.

I think that the ABS does not apply the brakes for you, but releases the brakes if you apply too much pressure, sensed by a difference in wheel rotation.

So, I think your ABS releases the both the left and right rear brakes simultaneously and to the same degree.

Yes, both rear wheels are on the same brake channel and same sensor.

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Thanks. So the rears operate as one unit.

I agree Jim the ABS does not apply but regulates.

Thanks again for increasing my understanding.