OBD · Fuel delivery

P0174 System too lean (bank 2)

Monitor

What this code means

P0174 is a generic OBD code shared by all manufacturers since 2001 for petrol and 2004 for diesel. It relates to: fuel delivery. The code tells you what the ECU measured as abnormal, not necessarily which part to replace.

Severity: Monitor. You can drive normally but get it checked in the coming weeks. It may fail an MOT or roadworthiness test.

Most common causes

  1. Intake air leak#1

    A hiss at idle with an unstable idle often means a split hose or intake gasket.

  2. Dirty mass air flow sensor#2
    Garage price: Mass air flow sensor £90 – £255
  3. Fuel pump#3
    Garage price: Fuel pump £190 – £530

Cost of related repairs

Independent garageMain dealer
Mass air flow sensor£90 – £255£115 – £365
Fuel pump£190 – £530£250 – £820

How to read this code

An OBD scanner plugged into the 16-pin socket under the steering wheel reads and clears codes. Bluetooth models cost £20 to £40. Clearing a code without fixing the fault is pointless: it comes back.

Related problems

Engine cranks but won't startCar judders when acceleratingLoss of power and limp modeBlack smoke when acceleratingRough or unstable idleCar keeps stalling

Frequently asked questions

What does code P0174 mean?

P0174: System too lean (bank 2). P0174 is a generic OBD code shared by all manufacturers since 2001 for petrol and 2004 for diesel. It relates to: fuel delivery. The code tells you what the ECU measured as abnormal, not necessarily which part to replace.

Can I drive with code P0174?

Monitor. You can drive normally but get it checked in the coming weeks. It may fail an MOT or roadworthiness test.

How much does it cost to fix P0174?

Mass air flow sensor: £90 – £255, Fuel pump: £190 – £530.

How to read this code

An OBD scanner plugged into the 16-pin socket under the steering wheel reads and clears codes. Bluetooth models cost £20 to £40. Clearing a code without fixing the fault is pointless: it comes back.