P0161: O2 Sensor Heater Circuit (Bank 2 Sensor 2)
The heater in the downstream oxygen sensor on bank 2 is not working properly.
What P0161 means
P0161 is the bank 2 downstream heater code, the partner to P0141 on bank 1. The engine computer powers a small heater inside the sensor after the bank 2 catalytic converter and checks its current draw or how quickly the sensor starts working. When the heater circuit is open, shorted or outside its expected current, P0161 sets. A heater that has burned out inside the sensor is the most likely cause. A blown fuse or broken wire can also do it, and downstream connectors live in a rough spot under the car where water and road salt cause corrosion. Because this sensor mostly grades the converter, you will usually not notice any change in how the car drives. The catalyst monitor will not finish, though, so the car may fail an emissions or readiness check. Shops verify fuse, power, ground and heater resistance, then replace the sensor or repair the wiring.
Common symptoms
- Check engine light on
- Usually no driveability problems
- Converter monitor not ready for emissions testing
- Possible higher emissions
- May appear with other heater codes
Most common causes
- Failed heater inside the bank 2 downstream sensor
- Blown heater fuse
- Broken heater power or ground wire
- Corroded connector under the car
- Engine computer heater driver fault (rare)
What to check yourself first
Check the heater fuse and look at the downstream connector for corrosion or a broken latch. Measure heater resistance at the sensor; an open circuit means the sensor needs to be replaced.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace oxygen sensor | $440-$523 | The usual fix, since the heater is not serviceable on its own. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For fuse, wiring or connector problems. |
| Check engine light diagnosis at a shop | $125-$183 | Confirms whether the sensor or circuit is at fault. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
- P0155 O2 Sensor Heater Circuit (Bank 2 Sensor 1)
- P0157 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
- P0135 O2 Sensor Heater Circuit (Bank 1 Sensor 1)
- P0430 Catalyst System Efficiency Below Threshold (Bank 2)