Was the car in an accident? If so you might need to replace the ETR's as well (the seat belt tensioners in the "B" pillar).
The sensor mounts to the tranny hump, about under the stereo, or at least it should be in a similar area on a 124. The grey cord runs along the passenger side of the hump and connects under the passenger side false floor in the foot well. It'
s the only red connector there. Be careful working that red 10 pin plug off, they will break if not careful - apparently not as tough as the black ones.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.