window wipers not returning when turned off

hi i have a 2002 club 8v estate.
the problems are
1] window wipers not returning when turned off, they can stop in any
position and i have to turn them on and off several times before they return
to the down position..

2] i have a warning light on the dashbord for the sensor in the cat
convertor. is there a way of finding out what is causing this without
spending loads at a vauxhal dealer just so they can tell me what it will
cost me to sort it out...

 

parking sensor, check the wipermotor assy has all it's connectors properly
seated.
else the pin has popped out or broken on the arm coming from the wiper cetre
shaft.

as advised

paperclip trick will tell you.
the fault code

mike