I am inclined to believe it was changed in '97 or '98 based on the thousands of posts I've read.
Also, all engine wiring harnesses are bad on all M104 engine W124's, W202's, and W140's from 93-95.
They seem to go out based on age not mileage, because it is the exposure to heat that brakes down the insulation.
If the car was mine and the engine wiring harness was original, I'd spend the $800 dollars or so and change it.
Go ahead. I dare you to do a search under "wiring harness" or "engine wiring harness" and you'll read the very sad posts of those who hadn't changed theirs out and some very expensive parts were damaged due to the bad harness.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".