OBD-II · Engine and powertrain (P)
P2198
Oxygen sensor signal stuck rich bank 2 sensor 1
What it means
The upstream (before the catalytic converter) lambda sensor on bank 2 keeps reporting a rich mixture when the ECU expects it to change. It can be a real rich mixture or a sensor or wiring fault. Confirm bank 2's location in the engine's service information.
Symptoms
- engine warning light
- higher fuel consumption
- possible hesitation or uneven running
- may fail the emissions part of the roadworthiness test
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | EVAP purge valve stuck open |
| 02 | leaking injector |
| 03 | high fuel pressure |
| 04 | fuel-diluted engine oil |
| 05 | faulty lambda sensor |
| 06 | signal wire short to voltage |
What to check, step by step
- 01Read short- and long-term fuel trims to confirm the ECU is pulling fuel
- 02Temporarily isolate purge flow using the OEM procedure and observe fuel trims; if disconnecting the line, seal the intake connection so the test does not introduce a vacuum leak.
- 03Check the engine oil for fuel dilution (fuel smell, rising level), common after many short trips
- 04Leak-test the injectors and check fuel pressure
- 05Check the sensor wiring, then substitute a known-good sensor if the mixture is correct