Code P0171 means the mixture is too lean on bank 1: there is too much air or too little fuel compared with what the control unit can compensate. The most common cause is an air leak.
What code P0171 means
Mixture too lean (bank 1).
Typical symptoms
- Unstable or hunting idle
- Loss of power and jerking
- Higher fuel consumption
- Hard starting
- Check engine light on
Most likely causes
| Cause | How common | What to do |
|---|---|---|
| Air leaks in the intake or hoses | Very common | Leak test and repair |
| Dirty or faulty MAF sensor | Common | Clean or replace |
| Low fuel pressure (pump, filter) | Common | Measure and replace |
| Clogged injectors | Common | Clean or replace |
| Lambda sensor | Less common | Check and replace |
| Leaking crankcase breather or brake servo | Less common | Check and repair |
How it is diagnosed
- Read short- and long-term fuel trims.
- Smoke test of the intake.
- Check the MAF and fuel pressure.
- Check injectors and lambda sensor.
Can you drive with code P0171?
Yes for short trips, but a lean mixture raises cylinder temperatures and can damage the engine: it has to be fixed soon.
How much does it cost to fix?
| Work | Indicative cost |
|---|---|
| Intake leak repair | €50-250 |
| MAF sensor | €80-300 |
| Fuel pump | €200-600 |
| Injector cleaning | €80-250 |
Figures are indicative market ranges, useful for orientation: the real cost depends on model, engine, parts chosen and labour hours. For an exact quote we need the vehicle registration number.
How MasterTuning helps
We read the real values of the control unit, not just the code: that is the difference between finding the faulty component and replacing parts by trial and error. After the repair we clear the error and check that it does not come back. Find the nearest centre or contact us.
Got code P0171 on your car? Book a diagnosis at the nearest MasterTuning centre.
Frequently asked questions
What does P0171 mean?
Mixture too lean on bank 1: too much air compared with the fuel.
What is the most common cause?
An air leak in the intake, followed by a dirty MAF sensor and low fuel pressure.
Is P0171 dangerous?
A prolonged lean mixture increases temperatures and can damage the engine.
How much does it cost to fix P0171?
From €50-250 for a leak to €200-600 for the fuel pump.
