what year is the bike?
i googled: "yzf-r125 ecu fault codes" which let me to this very forum:
Not sure if this bread has been done but here they are. To get the code, your orange engine management light will flash. There are to different flashes a long slow flash and a short fast flash. So 3 long flashes followed by 9 long would be code 39. 12 Crankshaft position sensor No normal...
www.r125forum.com
Also the service manual has it covered in detail on page 8-31 (again, use google to find a service manual - there's one for R125, will be close enough for this):
so according to this page the slow flashes are for the "10" value, and the short for the "1" value .. so 3 slow, 4 fast would be code 34, which doesn't appear to exist, hence asking what year bike.. in case it's a later one which has different codes (idk f that's a thing, idk much about WRs). Otherwise double check the sequence. It should be slow flashes first, then the fastt flashes, then a 3 sec gap before it repeats.
Hope that helps
tagging for future searches: R125 error codes R125 fault codes, R125 ECU codes, WR error codes, WR fault codes, WR ECU codes, error flashing, fault code
