Diagnostic manual index

obd2.help
AboutEspañol
OBD2.help›Powertrain›P0174

P0174

System Too Lean (Bank 2)

The engine is getting too much air or not enough fuel on bank 2. This can happen from a vacuum leak, a bad MAF sensor reading, or a fuel delivery problem.

SEV
3/5
DRIVE
CAUTION
DIY
$10–$250
SHOP
$120–$900

Quick answer

AI-CITATION READY

What it means

P0174 means the PCM has detected that bank 2 is running lean, meaning the measured air-fuel mixture contains too much air and not enough fuel. The code is set when fuel trims on bank 2 stay excessively positive as the PCM tries to add fuel to correct the condition.

Can you drive with it?

With caution. You can usually drive short distances, but the problem should be fixed soon. A lean condition can cause rough running, misfires, poor performance, and possible engine damage if ignored.

Most common causes

  • Vacuum leaks such as intake manifold gasket leaks, vacuum hose leaks, or cracked PCV hoses
  • Faulty or contaminated mass air flow (MAF) sensor reporting incorrect airflow
  • Plugged fuel filter or weak fuel pump causing low fuel delivery

Typical repair cost

DIY usually runs $10–$250. Typical shop repair lands around $120–$900, depending on the root cause.

01 / Definition

P0174 means the PCM has detected that bank 2 is running lean, meaning the measured air-fuel mixture contains too much air and not enough fuel. The code is set when fuel trims on bank 2 stay excessively positive as the PCM tries to add fuel to correct the condition.

02 / Drive status

With caution. You can usually drive short distances, but the problem should be fixed soon. A lean condition can cause rough running, misfires, poor performance, and possible engine damage if ignored.

03 / Symptoms

  • Check engine light on
  • Rough idle
  • Engine hesitation on acceleration
  • Reduced power
  • Misfires
  • Hard starting
  • Poor fuel economy
  • Stalling in some cases

04 / Causes

1Vacuum leaks such as intake manifold gasket leaks, vacuum hose leaks, or cracked PCV hoseshigh
2Faulty or contaminated mass air flow (MAF) sensor reporting incorrect airflowhigh
3Plugged fuel filter or weak fuel pump causing low fuel deliverymedium
4Plugged or dirty fuel injectors on bank 2 or across the enginemedium
5PCM software needs to be updatedlow

05 / Diagnostic sequence

  1. 01Check for other stored codes, especially P0171, misfire codes, and MAF-related codes.
  2. 02Review short-term and long-term fuel trim data for bank 2 and compare with bank 1.
  3. 03Inspect all vacuum hoses, PCV hoses, intake ducting, and intake manifold areas for cracks, loose connections, or leaks.
  4. 04Check for air leaks after the MAF sensor, including split intake boots and loose clamps.
  5. 05Inspect and clean the MAF sensor with proper MAF cleaner, then verify airflow readings are reasonable.
  6. 06Perform a smoke test on the intake system to find hidden vacuum leaks.
  7. 07Check fuel pressure and fuel volume against specifications.
  8. 08Test injector operation and consider injector cleaning if flow restriction is suspected.
  9. 09Verify oxygen sensor and fuel trim response after repairs.
  10. 10Check for applicable PCM software updates or service bulletins.

06 / Repairs

1Repair or replace leaking vacuum hoses, PCV hoses, or intake manifold gaskets$10–$400
2Clean the mass air flow sensor and inspect the intake tube and clamps for unmetered air leaks$10–$30
3Replace the mass air flow sensor if testing shows inaccurate airflow readings$80–$350
4Replace a clogged fuel filter or weak fuel pump if fuel pressure is below specification$40–$800
5Clean or replace restricted fuel injectors$20–$600
6Update PCM software if a manufacturer bulletin applies$80–$200

MFG / Manufacturer notes

These supplements add make-specific diagnostic framing. Pages without full matrix backing or lane approval stay guarded and canonicalize back here until they are explicitly approved for indexing.

  • Audi P0174

    Approved indexable child page

    Open

07 / Related codes

  • P0171
  • P0172
  • P0175
  • P0101
  • P0102
  • P0300

08 / FAQ

What does bank 2 mean?

Bank 2 is the side of the engine that does not contain cylinder 1 on V-type engines. On many inline engines, this code may not apply because there is only one bank.

Can a vacuum leak cause P0174?

Yes. A vacuum leak is one of the most common causes because extra unmetered air makes the engine run lean.

Can a dirty MAF sensor cause P0174?

Yes. If the MAF sensor underreports incoming air, the PCM may command too little fuel and set a lean code.

Will bad fuel injectors cause P0174?

Yes. Dirty or restricted injectors can reduce fuel delivery and create a lean condition.

Can low fuel pressure cause P0174?

Yes. A weak fuel pump or clogged fuel filter can reduce fuel supply enough to trigger this code.

09 / Source and method

DATA BASIS
OBD-II REFERENCE + OBD2.HELP
METHOD
STATIC VALIDATION
SAFETY
INFORMATIONAL

This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.

Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.

Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.