P015B
O2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1
Fuel & air metering (O2 sensor)
Generic OBD-II
Medium
What it means
P015B means the upstream oxygen/air-fuel sensor on Bank 1 (Sensor 1) takes too long to begin its lean-to-rich transition — a measured delay before it starts responding. Like other slow-response codes, it degrades fuel trims and emissions rather than stopping the car, so it's worth fixing to protect fuel economy and the catalytic converter.
Medium
Can I keep driving? Drivable, but fuel trims and emissions suffer — worth fixing soon to protect economy and the catalytic converter.
Common symptoms
What you'll notice
- Check-engine light on
- Slightly rough idle or occasional surging
- Higher fuel consumption
- Failed emissions/readiness test
Common causes
Most likely first
- Aged or contaminated upstream oxygen/air-fuel sensor (Bank 1, Sensor 1)Likely
- Corroded or damaged sensor wiring/connectorCommon
- Exhaust leak near the sensor skewing the readingCommon
- Fuel pressure or injector issue delaying the mixture changeLess often
- Unmetered air/vacuum leak on the intakeLess often
How to diagnose & fix
Work through it in order
- View the Bank 1 Sensor 1 signal live and watch the delay before it swings lean-to-rich.
- Inspect the sensor connector and wiring for corrosion or damage.
- Check for exhaust leaks near the sensor and intake vacuum leaks.
- Confirm fuel pressure and injector operation are within spec.
- Replace the upstream O2/AFR sensor if it responds late with everything else good, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P015B?+
Yes short-term. The engine runs, but a delayed sensor response worsens fuel trims and emissions, so repair it before it costs you economy or converter life.
Can I just clear P015B?+
It returns once the ECM re-checks the sensor's response timing. The slow sensor or contributing leak must be fixed.
Related codes
Often seen with P015B
Read & clear P015B yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX