P2196
O2 Sensor Signal Stuck Rich (Bank 1, Sensor 1)
The upstream oxygen sensor on bank 1 returns a constant rich signal under deceleration fuel cut-off where lean is expected. Often a contaminated sensor (silicone, oil, coolant) or short to ground that pulls the signal high in some sensor types.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
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.
- Upstream sensor contaminatedCommon
- Upstream sensor failed stuck richPossible
Parts involved
- Oxygen Sensor Upstream
P2196 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.