P0134O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The oxygen sensor before the catalytic converter on bank 1 (sensor 1) is the main control sensor for the mixture. It is either a switching sensor (about 0.1 V lean to 0.9 V rich) or a wide-band sensor that works with a pump current evaluated by an interface chip. P0134 means the sensor delivers no moving signal, typically because the circuit is open or the cell is cold or dead. The control module feeds a bias voltage, and that is all it sees: GM fails a signal stuck at 350–550 mV (or above 1700 mV with a 1.9 V bias) after warm-up, within about 15 s, or a cell resistance above 20 kΩ in hot exhaust; two trips. Subaru's wide-band sensor fails above 500 Ω cell impedance with immediate MIL. Ford's Bosch wide-band systems have used P2237 for this since 2011. A stored code usually switches mixture control to open loop and suspends adaptation and converter monitoring.
- What you may notice
- Check engine light on
- No mixture control (open loop), higher consumption
- Higher emissions, possible emissions test failure
- Likely causes
- LikelyOpen or high-resistance signal or ground wire, connector loose or corroded
- LikelySensor faulty (cell high-resistance, worn out)
- PossibleSensor heater faulty – sensor does not get hot enough
- RareExhaust leak ahead of the sensor or cracked sensor
- RareControl module bias or measuring circuit faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €50 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.