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
P2002
Powertrain
The ECU thinks the diesel particulate filter isn't trapping soot properly — or it can't measure…
Moderate
P0457
Powertrain
The EVAP leak test found the system wide open — almost always a loose, missing or worn gas cap.
Minor
P0455
Powertrain
The fuel vapor system can't hold vacuum at all — check the gas cap first, then hoses and valves.
Low
P0430
Powertrain
The bank 2 converter on a V6, V8 or split-exhaust engine isn't cleaning the exhaust well enough.
Low
P0496
Powertrain
Vapor is being drawn into the engine while purge is commanded off: almost always a purge valve…
Low
P0443
Powertrain
The ECU detected an electrical fault in the purge solenoid circuit: open, shorted or a bad…
Low