KlaroP0171
MODERATESystem Too Lean (Bank 1)
What this code means
The engine is getting too much air relative to fuel. The ECU has already enriched the mixture as far as it can. Likely causes: intake air leak, dirty mass air flow sensor or a weak fuel pump.
These codes concern the sensors that tell the control unit about the mixture: mass airflow, oxygen sensors, fuel trim corrections. They often point to an air leak or an ageing sensor rather than an outright failure.
How to read this code
- PPowertrain
- 0standardised code
- 1Fuel and air metering
- 71P0171
The letter P names the system: Powertrain. The digit 0 that follows marks a standardised code, shared by all manufacturers code. The next digit, 1, locates the fault: fuel and air metering.
What to do
Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.
Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back.
Nearby codes
- P0170Fuel Trim Malfunction (Bank 1)
- P0172System Too Rich (Bank 1)
- P0173Fuel Trim Malfunction (Bank 2)
- P0174System Too Lean (Bank 2)
- P0175System Too Rich (Bank 2)
- P0176Fuel Composition Sensor Circuit Malfunction
- P0177Fuel Composition Sensor Circuit Range/Performance
- P0178Fuel Composition Sensor Circuit Low Input