Emission control
P0134 — O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
The ECU receives no switching signal from the upstream oxygen sensor on bank 1. Without it, the engine runs in open loop and fuel mixture is not optimised.
Common causes
- Failed oxygen sensor
- Open circuit or broken wiring
- Blown fuse or failed heater supply
- Corroded connector
- Severe exhaust leak
Symptoms
- Higher fuel use
- Rough idle or poor performance
- Check engine light
- Possible black smoke
How to check
- Check the sensor connector, wiring and fuses
- Check the sensor heater circuit and supply voltage
- Read the live sensor value: a fixed voltage (around 0.45 V) suggests no activity
- Replace the sensor if the circuit is good
Can you keep driving?
Drivable for a short while, but the engine runs in open loop; repair it soon to avoid fuel waste and catalyst damage.
Related codes
Frequently asked questions
- What does P0134 mean?
- The upstream oxygen sensor on bank 1 is not producing a switching signal.
- Can a blown fuse cause P0134?
- Yes. A heater or sensor fuse problem can leave the sensor without proper operation.
General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.