Check Engine Code
P0140
O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
What P0140 means
P0140 means the downstream O2 sensor on Bank 1 isn't producing any signal — either the sensor heater is dead, the connector is unplugged, or the sensor itself is dead.
Symptoms
- CEL
- Slow readiness monitor completion
- Emissions test fail
Likely causes (most common first)
- Failed downstream O2 sensor
- Heater circuit failure (also sets P0141)
- Disconnected sensor
- Wiring issue
Can I keep driving?
Low — mostly emissions/economy
Typical repair cost
DIY fixes can start near $40 (parts only). Shop repairs for P0140 typically run up to $300 depending on the underlying cause and vehicle. Start with the most common cause — Failed downstream O2 sensor — before throwing parts at it.
Recommended parts & tools for P0140
Most common fix for P0140:
Oxygen (O2) sensorOur buyer’s guides cover the tools and parts that pair with AXLY:
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