P015B

O2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1

Q: 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.

Q: 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.

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.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P015B yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX