× Auto Repair Pros Member Benefits TechHelp Knowledge Base Forums Resources My iATN Marketplace Chat Pricing About Us Join Industry Sponsors Video Members Only Repair Shops Auto Pro Careers Auto Pro Reviews
Join Now
International Automotive Technicians Network

P0420 Diagnostic Trouble Code Discussion for May 2011

Catalyst Efficiency Below Normal (Bank 1)

Note: This is a professional automotive technician's resource.
Vehicle Owners: If you are seeking an automotive repair professional to service your vehicle, visit the iATN Repair Shop Finder.

Trouble Ticket Help Requests for DTC P0420
Help Request Posted
1999 Chevrolet Metro 1.0L No Start, Poor Idle Quality VIN: 2C1MR2267X
P0420: Catlayst efficiency low. This vehicle was towed into our shop as a no start. Customer stated he thought the timing belt jumped, it died at a stop light and he managed to get it started long enough to limp it off the road. He tried moving the distributor to get it to start with no luck...
May 06, 2011
2001 Pontiac Grand Prix GT 3.8L MIL Lamp on VIN: 1G2WP52K91
P0420: Catalyst System Bank 1 Low Efficiency. Car came in with cat code p0420.Check car and found rear o2 sensor damaged replaced and code came back.Fuel trims good.Graphed sensors and rear o2 stays flat but does move up and down when decelerating .Front o2 seems to be working okay.Freeze frame data show ...
May 17, 2011