20xe fault codes?

[Voodoo]

Friday night the Nova was working fine. Rolled into the garage to fit the bucket seats, then rolled back outside, all was fine. Yesterday, rolled into the garage to finish fitting the seats, ecu light comes on, although car is still running fine! Read the codes with the trusty paper clip and get:

16 - Knock sensor,
31 - Engine rpm signal (wich I assume is because the engine was not running),
55 - ECU FAULT (this one is really scaring me),
93 - Hall effect switch.

Am going to disconnect the ecu to reset and see what happens, but anyone have any idea of what could be going on?
:?:

[Voodoo]

UP!

[Voodoo]

Update:
The battery was disconected all day. Reconected, started the engine the light went on again, flashed the codes with the engine running and not running:

16 - Knock sensor,
55 - ECU fault.

93 - Hall effect switch was gone all together, and 31 - engine rpm signal was gone with engine running.
Now, this makes even less sense. The engine appears to be running fine, and why would one of the codes disapear?

Could it be dampness on the ecu due to the car not being used? A faulty wire? Any help, PLEASE?

[stan*]

There must b an error somewhere cos if the crank position sensor (Hall effect unit) was gone, the engine wouldnt run.
It is possible for there 2 b a fault and the engine to run fine, or seem 2 run fine, cos the ECU goes into "limp mode" where it uses preset readings 4 for the faulty component.
Sounds like dodgy/dirty/corroded connection/earth somewhere.