Emission Controls Trouble Codes: List & Fixes

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 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 P0457 Powertrain The EVAP leak test found the system wide open — almost always a loose, missing or worn gas cap. Minor

P2002 Powertrain The ECU thinks the diesel particulate filter isn't trapping soot properly — or it can't measure… Moderate P204F Powertrain The DEF/SCR system isn't cutting NOx the way it should; ignored, it leads to a severe speed… Moderate P207F Powertrain The ECM thinks the DEF in the tank is too weak or contaminated, often right after a refill. Moderate P20E8 Powertrain The DEF pump can't build or hold enough pressure; suspect a leak, frozen line, clogged filter… Moderate P20EE Powertrain The SCR catalyst isn't removing enough NOx; DEF quality, dosing, a NOx sensor or the catalyst… Moderate P2200 Powertrain The engine computer lost a usable signal from the NOx sensor ahead of the SCR catalyst on bank… Moderate P2201 Powertrain The upstream NOx sensor still communicates, but its readings don't match what the ECM expects. Moderate P2202 Powertrain The upstream NOx sensor reports a signal or internal circuit below its lower limit. Moderate P2203 Powertrain The upstream NOx sensor reports a value or circuit stuck above its upper limit. Moderate P2204 Powertrain The upstream NOx sensor signal keeps dropping out or jumping around for short moments. Low P2209 Powertrain The heater in the upstream NOx sensor can't reach or hold its working temperature properly. Low P229F Powertrain The NOx sensor after the SCR catalyst is sending believable-looking but wrong or sluggish… Moderate P2400 Powertrain The engine computer can't drive the EVAP leak detection pump – usually a broken wire, bad plug… Low P2401 Powertrain The leak detection pump's control wire reads too low – most often a wire rubbing through… Low P2401 Toyota · Powertrain In Toyota's key-off EVAP test, the canister module's leak detection pump didn't pull… Low P2402 Powertrain The leak pump's control line reads too high – usually a short to a 12-volt wire… Low P2404 Powertrain The switch that reports the leak pump's position isn't changing state the way it should during… Low P2419 Powertrain Too little voltage on the EVAP switching (vent) valve control wire – wiring or canister pump… Low P2420 Powertrain The switching valve in the EVAP canister pump module can't be switched – its control line stays… Low P2422 Powertrain The EVAP vent path is blocked, so the tank can't breathe – slow refueling and a whoosh when… Low P242F Powertrain The DPF is filling up with ash that regeneration can't burn off; it needs cleaning… Moderate P2440 Powertrain The valve that should seal the air pump off from the bank 1 exhaust stays open, letting hot… Moderate P2441 Powertrain The air pump runs after a cold start, but the bank 1 valve won't open – no fresh air reaches… Low P2442 Powertrain The bank 2 secondary air valve on a V engine doesn't seal, so exhaust pulses reach the air pump… Moderate P244A Powertrain The pressure drop across the DPF is lower than physically expected: a hose is off… Moderate P244B Powertrain The DPF is resisting exhaust flow far more than it should – usually a filter packed with soot… Moderate P2452 Powertrain The ECU has lost a usable signal from the DPF pressure sensor – usually a wiring, connector… Moderate P2453 Powertrain The DPF pressure reading doesn't make sense for the exhaust flow – most often a hose or tube… Moderate P2454 Powertrain The DPF pressure sensor's signal voltage has dropped below the lowest value a working sensor… Moderate P2455 Powertrain The DPF pressure signal is stuck above its valid range – a wiring fault, or a filter that's… Moderate