P0154
O2 Sensor Circuit No Activity / Slow Response (Bank 2 Sensor 1)
The ECU detects no switching activity or too slow a response from the upstream O2 sensor on bank 2. Typically aged or poisoned sensor, weak heater, or upstream exhaust leak.
- 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 aged or poisonedCommon
- Heater circuit weakPossible
- Exhaust leak before sensorPossible
Parts involved
- Oxygen Sensor B2s1
- Oxygen Sensor Heater Circuit
- Exhaust Manifold Bank2
P0154 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.