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All codes/P0174

P0174

System Too Lean (Bank 2)

Moderate severity

Your engine's computer has detected that the air-fuel mixture in the second bank of cylinders (if your engine has two) is too lean, meaning there's too much air or not enough fuel for proper combustion.

The powertrain control module (PCM) has detected that the engine is running too lean on Bank 2, meaning there is too much air or not enough fuel in the air/fuel mixture.

Common causes

  • Vacuum Leaks

    Leaks in vacuum lines, intake manifold gaskets, or PCV system can allow unmetered air into the engine, causing a lean condition, especially if localized to Bank 2.

    high

    Typical part cost: $50-300

  • Faulty Mass Air Flow (MAF) Sensor

    A dirty or failing MAF sensor can incorrectly report less air entering the engine than there actually is, leading the PCM to inject too little fuel for both banks.

    medium

    Typical part cost: $100-300

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First things to check

  1. 1Check for vacuum leaks using a smoke machine or by spraying carb cleaner around vacuum lines and intake manifold, focusing on Bank 2 side.
  2. 2Inspect the MAF sensor for dirt or damage; clean if necessary.

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Tools you may need

Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.

Illustration of a Bluetooth OBD2 adapter, not a product photo

Basic checks

Veepeak OBDCheck BLE

A Bluetooth LE adapter for reading standard engine codes and supported live data.

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Illustration of a Bluetooth OBD2 adapter, not a product photo

Regular diagnostics

vgate iCar Pro BLE 4.0

A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.

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Illustration of a Bluetooth OBD2 adapter, not a product photo

Another option

OBDLink CX

A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.

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Illustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.

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Related codes

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Frequently asked questions

What does 'Bank 2' mean?

Bank 2 refers to the side of the engine that does NOT contain cylinder #1. This code only applies to V-type or Boxer engines that have two separate exhaust banks.

If I have both P0171 and P0174, what's the likely cause?

If both codes appear, it strongly suggests a problem affecting both banks equally, such as a large vacuum leak common to both sides (e.g., intake manifold gasket), a faulty Mass Air Flow (MAF) sensor, or a general fuel delivery issue like a weak fuel pump or clogged fuel filter.

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