P013B
O2 Sensor Slow Response - Lean to Rich Bank 1 Sensor 2
Post-cat O2 sensor on bank 1 responds too slowly when mixture transitions from lean to rich. A drifted or sluggish lambda sensor lets the mixture run lean or rich without correction — fuel economy and emissions suffer immediately.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Common causes
Ordered by how often each turns out to be the cause.
- Sensor agedCommon
Parts involved
- Oxygen Sensor B1s2
P013B is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.