P019C
O2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 3
Bank 2 sensor 3 O2 sensor reacts only after delay during rich-to-lean transitions. 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 B2s3
P019C 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.