O2 Sensor Slow Response - Rich to Lean (Bank 1 Sensor 1)
This code means the PCM/ECM has detected a slow response from the sensor or actuator affecting o2 sensor. The problem is usually tied to fuel pressure control, injector operation, or the electrical circuit that commands the component. Depending on the failure, the engine may start hard, idle rough, hesitate, or lose power.
What You Might Notice
- Check Engine Light illuminated
- Reduced fuel economy
- Rough idle or hesitation
- Failed emissions test
- Possible rich or lean running condition
Most Common Causes
- 1
Faulty injector, regulator, pump, or fuel pressure sensor
- 2
Open, shorted, or corroded wiring/connectors
- 3
Restricted fuel filter or weak fuel supply
- 4
Vacuum leak or unmetered air entering the engine
- 5
PCM command/driver fault
How to Diagnose It
- 1
Check Faulty injector, regulator, pump, or fuel pressure sensor — Inspect for signs of failure and test before replacing.
- 2
Check Open, shorted, or corroded wiring/connectors — Inspect for signs of failure and test before replacing.
- 3
Check Restricted fuel filter or weak fuel supply — Inspect for signs of failure and test before replacing.
- 4
Check Vacuum leak or unmetered air entering the engine — Inspect for signs of failure and test before replacing.
- 5
Check PCM command/driver fault — Inspect for signs of failure and test before replacing.
How to Fix It
- 1
Check live data and fuel pressure against specifications
- 2
Inspect and repair wiring/connectors in the affected circuit
- 3
Test and replace the faulty injector, regulator, pump, or sensor
- 4
Repair vacuum leaks or fuel supply restrictions
- 5
Clear the code and confirm the repair with a road test
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