Dtc P0420
Thread Starter
Teching In
Joined: May 2004
Posts: 2
Likes: 0
From: Austin, Texas
Dtc P0420 I am getting DTC P0420 (TWC system low efficiency bank 1-A). I recently installed hi-flow cats. Can anyone tell me which side of the car is bank 1-A? Is it the cats or is it possibly the O2 sensors on that side?
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
damn...sounds like you car's been partaking in a few illegal activities.... hehe (420 get it ... 
)
What year car?
how many miles?
P0420: Catalyst System Efficiency Below Threshold (Bank 1)
It's probably the O2 since you just put a new cat in, however an easy test is to swap the rear O2 Sensors from bank 1 to bank 2 to see if the problem follows ... if it follows the O2 sensor then it's a bad O2 ... if it doesn't follow then the cat is bad
Regardless of what's wrong you have a few ways to fix... 1 legal 1 not so legal ... depends on your emissions in your area
If you still have to do the sniffer test then you'll wanna make sure your cat is working properly ... the cat should be warranteed from the company you bought it from so you can work with them to get it replaced.
if you only have to do the OBDII test then you should be able to get away w/either an O2 Simm or getting the rear O2 codes edited out.
)What year car?
how many miles?
P0420: Catalyst System Efficiency Below Threshold (Bank 1)
It's probably the O2 since you just put a new cat in, however an easy test is to swap the rear O2 Sensors from bank 1 to bank 2 to see if the problem follows ... if it follows the O2 sensor then it's a bad O2 ... if it doesn't follow then the cat is bad
Regardless of what's wrong you have a few ways to fix... 1 legal 1 not so legal ... depends on your emissions in your area
If you still have to do the sniffer test then you'll wanna make sure your cat is working properly ... the cat should be warranteed from the company you bought it from so you can work with them to get it replaced.
if you only have to do the OBDII test then you should be able to get away w/either an O2 Simm or getting the rear O2 codes edited out.
Thread Starter
Teching In
Joined: May 2004
Posts: 2
Likes: 0
From: Austin, Texas
Horist........Thanks. Great idea, I'll reset the codes and swap the sensors tonight and see if it follows it. 2003 50th AE Corvette with (of course) over 50,000 miles. Current mods include Vortex Rammer Air Intake, Granitelli MAF, WCC power duct, BBK ported throttle body, LSX fast intake, Corsa Indy pace car exhaust, Magnaflow X-pipe, Random high flow cats, and HPP III programmer.
