2005 C6, error code PO420
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6th Gear
Joined: Apr 2017
Posts: 6
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2005 C6, error code PO420
Drove the vet for about a hour, indicator light came on. Went to Advance auto. Shows PO420 error. Catalyst system efficiency below threshold. Anyone know about this. Fearing the worst.
Race Director
Joined: Sep 2009
Posts: 11,338
Likes: 2,437
From: Eastern
It's not usual for a catalitic converter to fail unless it has been introduced to leaded fuel, which will make it fail.
Generally speaking you can look at the temperature of the exhaust just before and just after the converter using an infrared temperature gun. The output should be about 100 degrees Fahrenheit hotter when the engine is fully warmed up to assure that the catalytic converter is working.
An Exhaust leak could cause a bad reading at the O2 sensor, giving you the P0420 code as well.
Check to see if the downstream side O2 sensor wires are Ok, not damaged.
Bank 1 is the left (Driver side) catalytic converter and O2 Sensors as per the pic
Burning Brakes
Joined: Dec 1999
Posts: 765
Likes: 11
Cruise-In I Veteran
You need to look at the O2 sensor values while the engine is warmed up and running.
The Bank 1 pre (S1) and post cat(S2) O2 sensor values should be moving around alot while city driving.
If the S2 (post cat) value is at 0, or stuck at a number, the sesnor or it's wiring is bad.
Now when driving at a steady 60-70 MPH on the interstate, watch ( or data log and watch later,) is the B1S2 (post cat) number relatively steady? Is it steady at 500 - 700 mV?
If the S2 number fluctuates similarly with the S1 number and doesn't stay consistent, the Cat Converter is bad.
Good luck and keep us posted,
The Bank 1 pre (S1) and post cat(S2) O2 sensor values should be moving around alot while city driving.
If the S2 (post cat) value is at 0, or stuck at a number, the sesnor or it's wiring is bad.
Now when driving at a steady 60-70 MPH on the interstate, watch ( or data log and watch later,) is the B1S2 (post cat) number relatively steady? Is it steady at 500 - 700 mV?
If the S2 number fluctuates similarly with the S1 number and doesn't stay consistent, the Cat Converter is bad.
Good luck and keep us posted,
