fault code p0420 (c3)

stevemc · Unread post by **stevemc** » 13 Nov 2010, 15:49

my 2002 1.4 c3 has the management light on ,the code is p0420
cat system below efficiency ,would this be the cat gone or a faulty lamda sensor

wheeler · Unread post by **wheeler** » 14 Nov 2010, 10:39

Has the car ever had a misfire/coil fault previously that was ignored for a while ? if so then the chances are it's the cat. Can be checked quite easily though by reading the live data from both the oxygen sensors with diagnostic gear.

woodywoodpecker · Unread post by **woodywoodpecker** » 14 Nov 2010, 12:07

Stevemc

Wheeler is right on the money with this one, just checked autodata and P0420 is catalytic converter , wiring to H02S2 first check oxygen sensors and wiring befor condeming the cat.

stevemc · Unread post by **stevemc** » 15 Nov 2010, 08:34

just checked the wiring to the 2 sensors ,both ok ,so where is the cheapist place to get a new cat ?

stevemc · Unread post by **stevemc** » 18 Nov 2010, 09:36

i have just put new plugs in and air filter,reset the ecu ,driven for 20 miles ,and the light has not come on ,last owner just told me he had not serviced it for 20000 miles ,hope it stays off