Worcester Bosch Greenstar CDi Classic System ErP fault codes

9 codes from the Worcester Bosch manual for the Greenstar CDi Classic System ErP gas boiler. Pick one for what it means, the likely causes and where to start.

Code	What it means
A7	Hot water NTC sensor defective
B1	Code plug not detected
C6	Fan speed too low
E2	CH flow NTC sensor defective
E9	Safety temp. limiter in CH flow has tripped
EA	Flame not detected/ignition lockout
F0	Internal error
F7	Flame detected even though appliance switched off
FA	Flame detected after gas shut off