Fuel & Air Metering Trouble Codes: List & Fixes

P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate 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 P0172 Powertrain The engine computer is pulling as much fuel as it's allowed on bank 1 and the mixture is still… Moderate

P0125 Powertrain The engine stayed too cold for too long to switch to closed-loop fueling based on the oxygen… Low P0126 Powertrain The engine didn't reach, or couldn't hold, the coolant temperature the ECU needs for stable… Low P0128 Powertrain The engine takes too long to warm up, which almost always points to a thermostat stuck open. Low P0130 Powertrain The upstream oxygen sensor on bank 1 sent a signal the engine computer could not make sense of. Low P0131 Powertrain The upstream oxygen sensor on bank 1 keeps reporting a voltage so low that it reads as a lean… Low P0132 Powertrain The upstream oxygen sensor on bank 1 reads too high: the engine is running rich or the signal… Moderate P0133 Powertrain The upstream oxygen sensor on bank 1 still works, but it reacts to mixture changes too slowly. Low P0134 Powertrain The upstream oxygen sensor on bank 1 isn't switching at all: its signal stays flat after… Low P0135 Powertrain The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty. Low P0136 Powertrain The oxygen sensor behind the catalytic converter on bank 1 is sending a signal that fails… Low P0137 Powertrain The oxygen sensor after the catalytic converter on bank 1 stays at a low, lean-looking voltage. Low P0138 Powertrain The oxygen sensor behind the converter on bank 1 reads too high, often from an internal short… Low P0139 Powertrain The oxygen sensor after the converter on bank 1 takes too long to react when fuel is cut… Minor P0140 Powertrain The oxygen sensor after the converter on bank 1 shows a dead-flat signal that never reacts. Low P0141 Powertrain The heater in the oxygen sensor behind the converter on bank 1 has failed or its circuit… Low P0150 Powertrain The upstream O2 sensor circuit on bank 2 is sending readings the ECU can't use, usually wiring… Low P0151 Powertrain Bank 2's front O2 sensor is stuck at a lean reading – often a manifold leak on that side… Low P0152 Powertrain Bank 2's front O2 sensor is pinned high – usually voltage leaking in from its heater wire… Moderate P0153 Powertrain Bank 2's front O2 sensor still switches, but too slowly between rich and lean; usually aged… Low P0154 Powertrain Bank 2's front O2 sensor never started switching; the ECU sees only a flat voltage from it. Low P0155 Powertrain The heater in bank 2's front O2 sensor, or its fuse, power feed or ECU-controlled ground, has… Low P0156 Powertrain The O2 sensor behind the bank 2 catalytic converter is sending an erratic or implausible signal. Low P0157 Powertrain The O2 sensor after the bank 2 converter reads near zero volts – often a nearby exhaust leak… Low P0158 Powertrain The O2 sensor after the bank 2 converter reads too high – often a short to heater power… Low P0161 Powertrain The heater in the O2 sensor behind the bank 2 converter isn't working, or its under-car wiring… Minor P0170 Powertrain Bank 1 fuel correction is far outside its normal window, lean or rich, and the ECU won't say… Moderate P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate P0172 Powertrain The engine computer is pulling as much fuel as it's allowed on bank 1 and the mixture is still… Moderate P0173 Powertrain Fuel correction on bank 2, the side without cylinder 1, is out of range or unstable, lean… Moderate P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate