I tried the trw2scan software and all I could get is "ECU Response Timeout" at each stage, no ISO Code identified etc.
I used a KKL/VAGCOM adaptor I bought off ebay which can switch which pin(s) the K-line is connected to, labelled 7 (engine), 3 (airbag), 1/9 (abs) or 12/13. Initially I thought the cable should be switched to airbag/pin 3 mode but when it didn't work I suspected this may not be the case. Now I can see that it's probably supposed to be 7(engine) because that's the only pin which is connected in my OBD2 to 3-pin adaptor! I have tested the cable on my engine ECU with multiecuscan and it worked fine.
Anyway, I tried all the switch positions, with a two wire harness only connecting K-line and ground, directly to the diagnostic harness, with the airbags and ECU connected and the ignition on. All I could only get "ECU Response Timeout"
I also double checked my airbag light _does_ remain lit when the ECU is completely removed.
Here is the KKL adaptor I used... Should it work or are the pins wrong?
So do we think the ECU is toasted? Surely it would be a coincidence for both that and wiring problem in the dash causing the airbag bulb to light? My thoughts are that I guess a grounding problem there could have fried the ECU? Or the same grounding problem could cause the communication interface problem?
I'm fed up with this problem now! I already wasted £40 on a failed MOT and I couldn't get this fixed in time for a retest. My mechanic has checked all the grounds and connections that usually fail, buy his snap-on diag unit couldn't communicate with this ECU. Then I wasted another £40 sending it to a crash data reset service, thinking that perhaps crash data was on it from the previous owner. There wasn't. Now I can't drive the car until it's fixed! I've driven the car with this light on for 5 years since I've owned it without any problem!
All help greatly appreciated!