Check engine light on: Codes, Causes & Fixes

P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate P0420 Powertrain The bank 1 catalytic converter no longer stores enough oxygen to clean the exhaust properly. Low P0101 Powertrain The MAF sensor's airflow reading doesn't match what the engine computer expects… Low P0113 Powertrain The intake air temperature signal is stuck at maximum voltage, which usually means an open… Low P0135 Powertrain The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty. Low P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate

P2238 Powertrain The pump-current wire of the upstream air-fuel sensor is being pulled low, usually by a short… Low P2243 Powertrain The ECM lost the reference-cell signal of the upstream wideband sensor, as if the wire were… Low P2262 Powertrain The engine computer commanded boost but saw almost none, pointing to a mechanical turbo… Moderate P2263 Powertrain Boost isn't tracking its target closely enough: too low, too high or too slow to respond. Moderate P2270 Powertrain The oxygen sensor after the catalytic converter won't show rich, even when the PCM deliberately… Low P2271 Powertrain The sensor after the converter stays rich even while coasting with the fuel cut off, when it… Low P2279 Powertrain Air is getting into the engine after the mass airflow sensor, so the computer isn't measuring… Low P2293 Powertrain The second fuel pressure control stage can't hold its target; on VW/Audi 2.0T often… Moderate 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 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