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
P0440
Powertrain
Catch-all EVAP code: the system failed its self-check. Start with the gas cap, then check hoses…
Minor
P0443
Powertrain
The ECU detected an electrical fault in the purge solenoid circuit: open, shorted or a bad…
Low
All codes (97)
P2457
Powertrain
The EGR cooler isn't cooling the recirculated exhaust enough – it's clogged, bypassed or low…
Moderate
P2458
Powertrain
A DPF regen took too long or never finished, usually from short trips or exhaust that won't get…
Moderate
P2459
Powertrain
The DPF is regenerating far more often than it should for the miles driven.
Moderate
P2463
Powertrain
The DPF is loaded with more soot than the ECU allows; it needs a regen or cleaning before it…
High
P246C
Powertrain
The DPF is so restricted that the ECM has cut engine power to protect the turbo, EGR system…
High
P2BAC
Powertrain
EGR has been shut off because of a fault, so NOx is above the limit; fix the EGR code stored…
Moderate
P3081
Volkswagen · Powertrain
The engine didn't warm up as fast as the ECU expected – most often a thermostat stuck open.
Low