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Fault code P0171 means mixture too lean (bank 1). The ECU is compensating by adding fuel because it detects too much air relative to the fuel.

Typical symptoms

• Rough idle
• Hesitation under acceleration
• Changed consumption
• Engine light on

Most common causes

• Intake leaks after the MAF sensor
• MAF sensor underestimating the flow
• Insufficient fuel pressure
• Partially blocked injectors
• Lazy lambda sensor
• Exhaust leaks before the sensor

How it is checked in diagnosis

• Reading short- and long-term fuel corrections
• Intake leak test (smoke)
• Checking fuel pressure
• Checking the lambda sensor signal

Can you drive with code P0171?

Yes, but the hesitation can get worse: to be fixed soon.

How MasterTuning helps

We read the real values from the ECU, not just the code: that is the difference between identifying the component responsible and replacing parts by trial and error. After the repair we clear the fault and check that it does not come back. Centres throughout Italy.

Read more: vehicle database · find an installer · what is ECU remapping

Do you have code P0171 on your car? Book a diagnosis at your nearest MasterTuning centre.

Frequently asked questions

What does fault code P0171 mean?

Code P0171 means mixture too lean (bank 1). The ECU is compensating by adding fuel because it detects too much air relative to the fuel.

Can you drive with fault P0171?

Yes, but the hesitation can get worse: to be fixed soon.

Is clearing code P0171 enough to fix it?

No: if the cause is still present the code comes back after a few kilometres. Clearing should only be done after the repair, with the diagnostic tool.

How much does it cost to fix code P0171?

It depends on the component responsible: the diagnosis is precisely what identifies it with real measurements, avoiding unnecessary replacements that cost far more than the correct repair.