Code 2337 knock limit exceeded. Done a few of these, last one only a couple of weeks ago, and I can get the right cylinder when I think about it carefully. Now done all four and ACR reports programming sucessful every time. Code numbers are correct, wouldn't matter if they were not for this problem. Each time glow/MIL continues to flash before attempting start. No other fault codes.

Will try Sykes help line tomorrow. Be handy to know if anyone else had the problem. Better still the answer.
Also have access to Modis and Launch so will try one of those.