Extruder starts but never stops (commissioning huxley)

Hi all, i'm new here, I have just built a reprap pro huxley with the meltzi PCB, all other functions are good, but the extruder when set to advance / reverse 5mm using the printer interface (following an M302 command to allow cold extrusion) never stops running.

Is this normal!?
Is there a list of all the G or M codes somewhere so I can see what they are/do!
What is the command to cancel or stop the extruder (other than to (software)disconnect/reconnect?)

The voltage is set to 0.55 on all steppers, thought the extruder is bigger should I set it higher, though it rotates fine at the moment (no filament in it yet) just it never stops - after several minutes!

Had an enjoyable time building it so far, I hope someone has an idea what might be the problem?
Tom

These are the default settings on the board:

Connecting...
start
Printer is now online.
echo:Marlin 1.0.1 RRP
echo: Last Updated: 2013-05-16-JMG | Author: eMAKER
echo: Free Memory: 11525 PlannerBufferBytes: 1232
echo:Using Default settings:
echoteps per unit:
echo: M92 X92.635 Y92.635 Z4000.000 E660.000
echo:Maximum feedrates (mm/s):
echo: M203 X500.000 Y500.000 Z5.000 E45.000
echo:Maximum Acceleration (mm/s2):
echo: M201 X1000 Y1000 Z50 E250
echo:Acceleration: S=acceleration, T=retract acceleration
echo: M204 S1000.000 T1000.000
echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum xY jerk (mm/s), Z=maximum Z jerk (mm/s), K=advance_k
echo: M205 S0.000 T0.000 B20000 X15.000 Z0.400 E15.000
echo: M206 X0.000 Y0.000 Z0.000
echo: M208 X155.000 Y150.000 Z90.000
echoID settings:
echo: M301 P12.000 I2.200 D80.000 W125
echo:Thermistor settings: M304 Hh Bb Rr Tt, H0=Bed, H1..n=nozzle, b=thermistor beta value, r=series resistor, t=thermistor resistance as 25C
echo: M304 H0
B4100 R4700 T100000 M304 H1
B3960 R4700 T100000
FPU Enabled no
transform correction not enabled
echoD init fail

Just seen a few others with the same issue 4 posts down. I'll have a look through tomorrow, some of the questions might have been answered there....

Hi,
I am having the same problem: how did you solve it?

Thank you.

Actually I found the solution in the other threads as well: M502 M500 and restart Huxley.

test...