P0134: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

What does P0134 mean?

The bank 1 upstream oxygen sensor's signal is not moving. It sits near a fixed voltage even though the engine is warm. Sensor 1 is the upstream sensor, mounted before the catalytic converter; the engine computer uses its signal to adjust fuel mixture. With no feedback, the computer falls back to a preset fuel mixture.

Generic OBD-II definition: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1). Confirm applicability in your vehicle service information.

Common causes

• Sensor dead or not heating up (check for a heater code too)
• Open signal wire or unplugged connector
• Ground problem at the sensor
• Large exhaust leak

Symptoms

• Check engine light
• Possible rich running or black smoke
• Poor fuel economy

Can I keep driving with P0134?

Severity: Medium Drive gently and get it diagnosed soon.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Check whether P0135 is also stored; a dead heater can keep the sensor too cold to respond
• Check that the connector is fully seated and the pins aren't corroded
• Measure the signal at the connector with a multimeter
• Replace the sensor if the circuit tests good