Share a caseSign in
FuelSeverity Medium: diagnose soon

P0174System Too Lean (Bank 2)

What it means

The ECU is adding much more fuel than normal on bank 2 and has reached its limit: the engine is getting too much air or too little fuel.

Symptoms

  • Rough or hunting idle
  • Hesitation when accelerating
  • Sometimes misfires

Common causes

  • Vacuum or unmetered air leak after the MAF (gaskets, hoses, PCV valve)
  • MAF sensor under-reading (dirty)
  • Low fuel pressure: weak pump, clogged filter
  • Restricted injectors
  • Exhaust leak before the upstream oxygen sensor

What to check first

  1. Compare long-term fuel trims at idle and at 2,500 rpm: high at idle only points to a vacuum leak, high everywhere to MAF or fuel supply
  2. Smoke-test the intake
  3. Check fuel pressure under load
Can I drive with P0174? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0174

Mass air flow sensor (MAF)Wiring, typical values, multimeter and scope tests

Cases with P0174 (0)

Share yours

No published cases with this code yet.

Colleagues asking about P0174

Ask for help

Stuck on P0174? Describe what you measured and ask the community.

P0174: questions and answers

What does P0174 mean?

P0174: System Too Lean (Bank 2). The ECU is adding much more fuel than normal on bank 2 and has reached its limit: the engine is getting too much air or too little fuel.

What are the symptoms of P0174?

Rough or hunting idle. Hesitation when accelerating. Sometimes misfires.

What causes P0174?

Vacuum or unmetered air leak after the MAF (gaskets, hoses, PCV valve). MAF sensor under-reading (dirty). Low fuel pressure: weak pump, clogged filter. Restricted injectors. Exhaust leak before the upstream oxygen sensor.

How do you diagnose P0174?

1. Compare long-term fuel trims at idle and at 2,500 rpm: high at idle only points to a vacuum leak, high everywhere to MAF or fuel supply 2. Smoke-test the intake 3. Check fuel pressure under load

Can I drive with P0174?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.