P015BO2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- The upstream oxygen sensor (sensor 1, before the catalytic converter) is the main control sensor for the air-fuel mixture. 'Delayed response' means the sensor starts reacting too late, or does not reach the target level at all, after the mixture has changed. This code covers the lean-to-rich direction, tested when fuel returns or the control module briefly enriches the mixture. GM measures the upstream switching sensor's delay while the mixture is enriched for the downstream tests and fails a filtered delay above about 0.58 s (fallback 1.9 s) after one trip; the test needs the rich-to-lean counterpart P015A completed first. CARB requires separate detection of slow and delayed faults in each direction (phased in from 2009 for downstream and 2011 for upstream sensors).
- What you may notice
- Check engine light on
- Slightly higher consumption or rough idle possible
- Higher emissions, possible emissions test failure
- Often no noticeable symptoms
- Likely causes
- LikelyUpstream oxygen sensor aged or poisoned (silicone, oil, coolant, soot)
- PossibleExhaust leak ahead of the sensor (manifold, flange)
- RareMixture fault: intake air leak, injectors, fuel pressure, air flow sensor
- RareSensor heater weak, sensor too cold
- RareConnector, wiring or control module software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €80 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.