Code
P0134
Emissions
Oxygen sensor no activity detected — Bank 1 Sensor 1
The upstream oxygen sensor never changes voltage — no signal activity.
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Most likely causes
- Faulty O2 sensor
- Wiring fault
- No heater operation
Symptoms you may notice
- Check engine light
- Runs rich longer
- Worse fuel economy
Checks to run
- Watch O2 voltage at 2,500 rpm for switching
- Test the sensor
- Check wiring
Tools you may need
OBD-II scanner
Multimeter
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.
Related codes in Emissions
P0420