Code P0171 indicates that the engine is running with a lean mixture (too much air, not enough fuel). This fault is quite common in petrol engines and can lead to a loss of power, stuttering, or an illuminated check engine light.
What Does Code P0171 Mean?
The P0171 code means that the engine control unit has detected an incorrect air/fuel ratio on Bank 1 (cylinders on one side). The engine is receiving too much air or not enough fuel.
Common Symptoms
- Check engine light illuminated
- Unstable idle
- Loss of power
- Stuttering on acceleration
- Increased fuel consumption
Most Common Causes of Code P0171
1. Air Leak (Intake Leak)
A cracked hose or faulty gasket can allow too much air to enter.
2. Dirty Mass Air Flow (MAF) Sensor
A dirty MAF sensor sends incorrect information to the engine control unit.
3. Clogged Injectors
If the injection is insufficient, the mixture becomes lean.
4. Weak Fuel Pump
Insufficient fuel pressure leads to a lack of supply.
5. Faulty Lambda Sensor
A failing sensor can skew the mixture correction.
Can You Drive with Code P0171?
It is possible to drive temporarily, but a lean mixture can:
- Damage the valves
- Overheat the engine
- Cause deterioration of the catalytic converter
How to Diagnose Accurately?
- Check intake hoses
- Clean the MAF sensor
- Check fuel pressure
- Analyse fuel trim values via OBD
Estimated Repair Costs
| Cause | Estimated Cost |
|---|---|
| MAF Sensor Cleaning | £50 to £150 |
| MAF Sensor Replacement | £150 to £400 |
| Injectors | £200 to £800 |
| Fuel Pump | £300 to £900 |
| Lambda Sensor | £100 to £300 |
Key Takeaway
The P0171 code indicates an imbalance in the air/fuel mixture. A quick inspection can prevent more significant damage and costly repairs.
