I have a 1995 S350D which had a new head gasket installed several months ago. The mechanic did not disconnect the battery and the wiring harness insulation crumbled upon movement and shorted out. This caused several fuses to open. The wiring harness and fuses have been replaced as has the ECM. However the engine shutdown does not function, the AC does not work, and the tachometer does not indicate. The OEM code reader indicates the ECM is at fault but a new unit did not resolve the problem. All wires have been traced relays traded out, all yielding no results. I'm stumped, the wiring diagrams have been traced meticulously. Any help would be appreciated, any technicians out there that want a real challenge?

Optional Information:
1995 Mercedes-Benz S350D 3500 Diesel

Already Tried:
ECM, wiring harness, fuses, relays.