Hi

It will be a Reflex AC

Battery been checked for loose / corroded cell straps etc?

C16 = Accelerator pedal activated / error at start up
C22 = Tilt joystick activated at start up

Also check the wires on the back of the keyswitch are not loose OR more likely the actual terminals on the key switch can come loose, if you can twist / turn the terminals on the back of the keyswitch it needs replacing.

What happens with this fault is as you drive the truck the faulty keyswitch briefly breaks the electrical supply to the main A5 card so the truck will stop & then goes through the start up sequence, as the accelerator pedal or a joystick is likely to being used at the time it will throw the error code.

Sometimes you will see the dash display briefly go off then come on again but you have to be quick to spot it.

I've replaced lots of faulty key barrels on older Reflex's.