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Poor fuel economy: Codes, Causes & Fixes

When mpg drops without a change in driving habits, typical culprits are a thermostat stuck open (P0128), a slow oxygen sensor, a coolant temperature sensor reading too cold, dragging brakes or simply low tire pressure. Several of these set no code at first, so compare your recent fill-ups and check tire pressure against the placard on the driver's door jamb. A stored code, if present, narrows the search considerably.

146Codes
2.4Average severity
2%High or critical
17%DIY-friendly
Severity distributionSeverity distribution

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P0135 Powertrain The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty. Low 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 P0113 Powertrain The intake air temperature signal is stuck at maximum voltage, which usually means an open… Low

All codes (3)

All Severity 3+ Severity 4+
P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High P2463 Powertrain The DPF is loaded with more soot than the ECU allows; it needs a regen or cleaning before it… High P3000 Toyota · Powertrain Toyota's hybrid computer flags a fault in the high-voltage battery system and limits hybrid… High

Symptoms

Check engine light on 558Loss of power 214Rough idle 184Limp mode 165Engine stalling 133Car won't start 123Harsh or slipping shifts 80ABS / traction light on 65Fuel smell 34Check engine light flashing 22