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16804 P0420 Catalyst System,Bank1 Efficiency Below Threshold

Posted: Sat Nov 22, 2014 6:42 pm
by calumvw
I've been tormented with this code long enough! I used Cataclean and it's popped up again today. I haven't had codes for the 02 sensors, I reset the CEL after the Cataclean treatment now that the CEL is back on I checked the readiness codes the only one that hadn't passed was the SAIP which said failed or incomplete, I know that it will pass in time as it always has before.
Any suggestions, I have a relay and 40 amp fuse to fit in the ECU box for the SAIP to eliminate that.

B5.5 1.8t engine code AWT.