OBD-II code · Powertrain (generic)
P015B O2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1
Pre-cat O2 sensor on bank 1 reacts only after delay when mixture switches lean to rich. A drifted or sluggish lambda sensor lets the mixture run lean or rich without correction — fuel economy and emissions suffer immediately.
Is it safe to drive with P015B?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySensor aged
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Oxygen Sensor B1s1
Related codes
- P013FO2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 2
- P014BO2 Sensor Delayed Response - Lean to Rich Bank 2 Sensor 2
- P015DO2 Sensor Delayed Response - Lean to Rich Bank 2 Sensor 1
- P019BO2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 3
- P019DO2 Sensor Delayed Response - Lean to Rich Bank 2 Sensor 3
- P0158O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
- P0159O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
- P015AO2 Sensor Delayed Response - Rich to Lean Bank 1 Sensor 1
- P015CO2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 1
- P015EExcessive Time to Enter Closed Loop Fuel Timing Control
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.