What year?

I've researched adding ASR to my 97 C280

All will have the triangle due to having the same dash cluster.

With ASR, above the radio ( the hazard light switch area ) they should be a switch with a snow tire or ASR off. ( If ESP it will just say ESP off )

Have a look at the under hood ABS unit, a non ASR / ESP car will have 5 lines ( 2 from the master cyl , 2 for each front wheel and _1_ for the rear )

An ASR / ESP car will have 6 ( each rear has it's own line )

The ASR / ESP computer is part of the ABS computer, on the 97 it is bolted to the engine computer.

ASR / ESP cars will have a speed sensor at each rear wheel that reads off the outer CV , non ARS cars will have a speed sensor on the differential between the pinion bearings.

I've looked into adding ASR, it requires:

Changing the rear outer CV / adding a tone ring.

Rear speed sensors / wiring to the ASR computer.

Repinning the ASR computer plug not just adding wires,

replace ABS unit with ASR capable unit,

replace ABS computer with ASR unit

adding / splitting rear brake line.

I "think" that should get things going and I'm hoping the ECU / trans control / Dash does not need reflashed.

ESP might also need a steering angle sensor and other things I'm not aware of.