2004 Cadillac P0420 Code

2004 CADILLAC DEVILLE
V8
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PMASPKS
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  • 7 POSTS
"Catalyst System Efficiency Below Threshold (Bank 1)". Is this something I can repair myself? I have already changed out all sensors, replaced the catalytic converter, and had the torque converter replaced, now this pops up after about 250 miles.
Dec 12, 2010 at 1:12 AM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
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RASMATAZ
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Go to this link: https://www.2carpros.com/trouble_codes/obd2/P0400
Dec 12, 2010 at 1:20 AM
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WRENCHTECH
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It's pretty rare that this is caused by anything but a bad converter. The criteria for setting it is that the front and rear 0/2 sensors have to pretty much mirror each other among other things and that won't happen if the cats are working. I did see it happen once from a crack at the front of the converter letting 0/2 in.
Dec 12, 2010 at 1:31 AM