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 distribution

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P0302 Powertrain Cylinder 2 keeps misfiring. On inline engines it's a middle cylinder, so rule out coolant… Moderate P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate P0301 Powertrain Cylinder 1 is repeatedly failing to fire. The cause is almost always its coil, plug, injector… Moderate P0014 Powertrain The bank 1 exhaust cam won't follow its target and stays too far advanced; think oil, valve… Moderate P0101 Powertrain The MAF sensor's airflow reading doesn't match what the engine computer expects… Low P0093 Powertrain Rail pressure is dropping faster than injection explains: fuel may be escaping. Stop and check… Critical

All codes (47)

All Severity 3+ Severity 4+

P1778 Nissan · Powertrain The Jatco CVT's step motor is being commanded, but the pulley ratio isn't following it as it… High P17F0 Nissan · Powertrain The TCM detected judder it blames on the CVT itself, usually belt or pulley slip inside… High P2100 Powertrain The computer can't push current through the throttle motor – the circuit to the throttle body… High P2104 Powertrain A fail-safe has locked the engine at idle and the gas pedal no longer works – another code… High P2107 Powertrain The processor supervising the electronic throttle failed its self-check – a computer fault, not… High P2112 Powertrain The PCM asked the throttle to open, but it stayed shut – the engine can't get air, so it bogs… High P2146 Powertrain The shared power feed for one group of injectors is open, so every injector in that group has… High P2149 Powertrain The shared supply to the second injector group dropped out, often an intermittent wiring fault… High 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 P3000 Toyota · Powertrain Toyota's hybrid computer flags a fault in the high-voltage battery system and limits hybrid… High 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 558 Rough idle 184 Limp mode 165 Poor fuel economy 146 Engine stalling 133 Car won't start 123 Harsh or slipping shifts 80 ABS / traction light on 65 Fuel smell 34 Check engine light flashing 22