P0134: O2 Sensor Circuit No Activity Detected — Bank 1 Sensor 1
What to do
Expect poorer economy and emissions. If a heater circuit code is also stored, the heater is likely the root cause and the sensor may be fine electrically but simply too cold to work.
What this code means
The upstream bank 1 sensor signal is not moving at all — it sits at a fixed value instead of switching. A dead heater is a frequent cause, because a sensor that never reaches operating temperature never starts switching; check for an accompanying heater code before assuming the sensing element itself has died. An open circuit in the signal wire produces the same flat trace.
Likely causes
Start here
- Faulty oxygen sensor · easy
- Failed oxygen sensor heater element · easy
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
Less common
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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