I have a 2004 Astra GSi Turbo in which the Emmision light keeps coming on. Its happened 3 times now as when i clear the code it turns the light off then around a week or so later it comes back with the same fault code. The code is the following:
P0420 Catalyst System Efficiency Below Threshod (Bank 1)
The car has a full 2.5 exhaust system, with vortex sports cat and pre cat removed, so guessing this may be the problem? Any help would be great, Thanks!