The P1135 code in your 2021 Lexus IS indicates a problem with the air/fuel ratio sensor circuit on bank 1. This Toyota/Lexus-specific code signals an issue with the wide-band oxygen sensor that monitors exhaust gases before the catalytic converter.
Understanding A/F Ratio Sensors
Unlike traditional O2 sensors that read rich/lean, air/fuel ratio sensors provide precise linear feedback allowing the ECU to fine-tune fuel delivery. P1135 indicates bank 1 sensor (cylinder 1 side) has a circuit issue.
Common Causes of P1135
- Faulty A/F ratio sensor
- Sensor heater circuit failure
- Wiring damage to sensor
- Connector corrosion
- ECU input circuit problem
- Exhaust leaks affecting readings
Symptoms of A/F Sensor Issues
- Check engine light on
- Poor fuel economy
- Rough running
- Hesitation on acceleration
- Failed emissions test
- Possible rich or lean condition
Lexus IS Performance
The IS is a performance-oriented vehicle requiring precise fuel control. A/F sensor issues affect both performance response and fuel efficiency.