4agze check light puzzle

[Mr Revhead]

right first up, im a complete electrical n00b....

my aw11 has been converted tp n/a 4age with afm s/c gear.

the engine check light comes on when the revs first get to 23-2500.
iv checked the codes and its all clear.....

so what can cause the check light to come on and not store any codes?

[Mr Revhead]

well thanks to master sparky matt dunn problem solved.
seems if the terminals are bridged while running after the light has come on is shows the codes.

and in my case, its the knock sensor... or lack of one