After having the bike for 5 1/2 years the battery died. I replaced with one like for like. After changed the engine fault light came up after about 30secs of running. I cleared this by turning ignition on/off 4 times. Then running and giving it a few more revs. On the dash it shows volts at 13.8v when running. I double checked the terminals no loose connections there. I thought it would help after went out for 40 mile ride for an mot to give it a good charge. But the light came back on after I stopped for mot, until I did the ignition reset again and it road back ok. Qs is working as expected and bike is riding same as ever.
Assuming you followed the correct sequence for disconnection (negative first, negative last) and didn't generate any shorts, I'd do the following: Take the battery off and charge it. Removing it will do a hard reset of the ECU. When reconnected, check the charging voltage (preferably with a multimeter) at 3000-4000rpm (not from cold!). You should be getting a reading of between 14 to 14.5V. The dash reading won't be accurate although 13.8V sounds acceptable. This is just general principles and not specifically related to your bike but the basics have to be eliminated first.
Thanks will have to give that a go. Yes battery changed as recommended it had been on the shelf a while at halfords so could of been a bit flat.
Good stuff. Adding the acid pack will generally give around 80% charge but charging prior to first use is recommended for longevity. As regards the warning light, disconnecting the negative lead and leaving for around 30 minutes will remove all residual current from the ECU. Your 'soft reset' works but only for a while. Hopefully this will clear it. Otherwise I guess you're into reading fault codes.
