The amount of ETR a car has depends on year, model, and possibly version in non US models. I am pretty sure that whatever diagnostics that are available are through the AB socket.

For US 124 models there are no specific codes for emergency tentioning retractor. There is a note in the DM (diagnostic manual) that states to do the ETR electrical test if either code 3 or code 4 won't reset.

The electrical test involves using a BOB ( break out box) to test the ETR squibs for resistance; 2-5ohms, isolation resistance; greater than 20kohms and wiring check.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician