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Loss of power: Codes, Causes & Fixes

Noticeable loss of power usually has one of a few causes: the engine computer has entered limp mode, a turbocharged engine is underboosting (P0299), airflow is restricted by a dirty MAF sensor or clogged air filter, fuel pressure is low, or the exhaust is blocked by a failing catalytic converter or full diesel particulate filter. Read all stored codes and freeze-frame data first – they usually show which of these paths to follow.

214Codes
3.1Average severity
22%High or critical
9%DIY-friendly
Severity distributionSeverity distribution

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P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High 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 P0101 Powertrain The MAF sensor's airflow reading doesn't match what the engine computer expects… Low P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate

All codes (177)

All Severity 3+ Severity 4+
P219B Powertrain One cylinder on bank 2 runs off the mixture of the other cylinders on that side of the engine. 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 P2228 Powertrain The baro sensor signal is below its valid range, as if the car were far higher than any road… Moderate 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 P2293 Powertrain The second fuel pressure control stage can't hold its target; on VW/Audi 2.0T often… Moderate 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 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 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 P3000 Toyota · Powertrain Toyota's hybrid computer flags a fault in the high-voltage battery system and limits hybrid… High P3190 Toyota · Powertrain The hybrid computer asked the gas engine for power and got less than expected. Moderate U0101 Network The engine computer and other modules stopped hearing from the transmission control module. High U0105 Network The PCM lost contact with the separate module that fires the injectors, common on diesel… High U0107 Network The engine computer can't reach the module that drives the electronic throttle, so power is cut… High U0109 Network The PCM lost contact with the module that controls fuel pump speed; stalling or no-start can… High U0110 Network The hybrid/EV system lost contact with the module that runs electric drive motor A. Critical U0115 Network Modules lost contact with the second engine computer on vehicles that use two of them. High

Symptoms

Check engine light on 558Rough idle 184Limp mode 165Poor fuel economy 146Engine stalling 133Car won't start 123Harsh or slipping shifts 80ABS / traction light on 65Fuel smell 34Check engine light flashing 22