My 1990 w124 2.5 has "electronic locking differential " in its spec sheet, but it doesn't seem to work as the triangle light never turns on slippery surfaces. I also can't find the hydraulic reservoir, any ideas? Is it possible I have ASR and they worded it wrong?

Likely integrated into the power steering pump check if you have 4 hoses going to the pump.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

The reservoir should be between the ABS pump and LHD driver side fender.

Sixto
MB-less

Ya, you can't miss it. It's the same one used on cars with self levelling suspension (and the ASD system uses the same fluid).

Does the triangle light come on for a moment when you start the car?

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

ASD = four hoses to/from the power steering pump (two circuits, one for steering and the other circuit for the hydraulic locking differential.

ASR = four wheel speed sensors, one at each wheel. If wheel slip is detected at either rear wheel, the ABS system applies the brake to that wheel to reduce wheel spin and force power to the other rear wheel. Non-ASR cars have a single speed sensor for the rear axle on the differential.

"Electronic Locking Differential" implies ASR, no?

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC