A little advice needed please

[Michael robinson]

hi yesterday my engine light came on and I tested it with the obd2 fault code reader it's coming up with P0420 Catalyst System Efficiency Below Threshold (Bank 1)

I was just wondering if there's any way I can test weather it's my cat or the sensor ?

Av just bought new hfc's from Tarmac so I can change my cat's , but if i could test the sensors to find out if the sensors are nackered before putting the hfc's in it would save me an labour changing them all together .

Cheers

[Zugara]

Swap them over, see if you get a fault code for bank 2.