Emission Controls Trouble Codes: List & Fixes
P04xx codes cover auxiliary emission controls: exhaust gas recirculation (EGR), secondary air injection, catalytic converter efficiency and the evaporative emission (EVAP) system. They seldom affect how the car drives, but they will usually fail a smog check or emissions test. For small EVAP leak codes, start with the simplest check – a loose, damaged or wrong gas cap – before a smoke test of the system.
97Codes
2.2Average severity
2%High or critical
20%DIY-friendly
Severity distribution
Most viewed
P0420
Powertrain
The bank 1 catalytic converter no longer stores enough oxygen to clean the exhaust properly.
Low
P0430
Powertrain
The bank 2 converter on a V6, V8 or split-exhaust engine isn't cleaning the exhaust well enough.
Low
P2002
Powertrain
The ECU thinks the diesel particulate filter isn't trapping soot properly — or it can't measure…
Moderate
P0442
Powertrain
The EVAP system leaks through an opening of about 0.040 inch — a cracked hose, loose joint…
Minor
P0446
Powertrain
The canister vent valve isn't doing what the ECU commands — electrically or because the vent…
Minor
P0456
Powertrain
The EVAP system has a tiny leak, about 0.020 inch — the hardest EVAP leak to find, and often…
Minor