HO2S Bank 1 Sensor 1 Air/Fuel Ratio Too Lean
2014-2021 Mazda Mazda6 2.5L I4
Description
The upstream heated oxygen sensor on Bank 1 indicates a persistent lean air-fuel ratio. The PCM has been unable to correct the lean condition through fuel trim adjustments.
Symptoms
- Check Engine Light
- Rough idle
- Hesitation
- Poor acceleration
- Possible misfires
Common Causes
- Vacuum leak in intake system
- Low fuel pressure
- Dirty or faulty MAF sensor
- Faulty O2 sensor reading lean incorrectly
- Exhaust leak before sensor
Diagnostic Steps
- Check for vacuum leaks with smoke test
- Monitor fuel trim values on scan tool
- Check fuel pressure at idle and under load
- Clean MAF sensor
- Inspect for exhaust leaks near O2 sensor
Repair Notes
Repair vacuum leaks; check fuel pressure and MAF sensor; replace the O2 sensor if faulty.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0011Intake Camshaft Position Timing Over-Advanced Bank 1
- P0012Intake Camshaft Position Timing Over-Retarded Bank 1
- P0013Exhaust Camshaft Position Actuator Circuit/Open Bank 1
- P0014Exhaust Camshaft Position Timing Over-Advanced Bank 1
- P0015Exhaust Camshaft Position Timing Over-Retarded Bank 1
P1131 on Other Vehicles
Common Questions
What does code P1131 mean on a 2014-2021 Mazda Mazda6?
P1131 stands for "HO2S Bank 1 Sensor 1 Air/Fuel Ratio Too Lean". The upstream heated oxygen sensor on Bank 1 indicates a persistent lean air-fuel ratio. The PCM has been unable to correct the lean condition through fuel trim adjustments.
What are the symptoms of P1131 on a Mazda Mazda6?
Common symptoms of P1131 include: Check Engine Light, Rough idle, Hesitation, Poor acceleration, Possible misfires.
What causes P1131 on a 2014-2021 Mazda Mazda6?
Common causes of P1131 include: Vacuum leak in intake system, Low fuel pressure, Dirty or faulty MAF sensor, Faulty O2 sensor reading lean incorrectly, Exhaust leak before sensor.