OBD · Fuel delivery
P0171 System too lean (bank 1)
What this code means
P0171 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.
Most common causes
- Intake air leak#1
A hiss at idle with an unstable idle often means a split hose or intake gasket.
- Dirty mass air flow sensor#2
- Fuel pump#3
- Dirty or faulty injector#4
Cost of related repairs
| Independent garage | Main dealer | |
|---|---|---|
| Mass air flow sensor | £90 – £255 | £115 – £365 |
| Fuel pump | £190 – £530 | £250 – £820 |
| Diesel injector | £245 – £650 | £310 – £975 |
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
Frequently asked questions
What does code P0171 mean?
P0171: System too lean (bank 1). P0171 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 P0171?
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 P0171?
Mass air flow sensor: £90 – £255, Fuel pump: £190 – £530, Diesel injector: £245 – £650.
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.