OBD-II · Engine and powertrain (P)
P0134
Oxygen sensor no activity bank 1 sensor 1
What it means
The ECU detects no expected activity from the upstream lambda sensor on bank 1. Interpret its response according to sensor type: a wideband sensor need not show narrowband voltage switching.
Symptoms
- engine warning light
- higher fuel consumption
- possible hesitation or uneven running
- may fail the emissions part of the roadworthiness test
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | unplugged sensor |
| 02 | failed lambda sensor |
| 03 | open signal wire |
| 04 | heater fault |
| 05 | ECU input fault |
What to check, step by step
- 01Check the sensor is plugged in and the connector is dry and undamaged
- 02Check the heater fuse and supply: a cold sensor stays inactive
- 03Watch the signal with the engine fully warm and held above idle
- 04Check the signal wire for an open circuit back to the ECU
- 05Replace the sensor if the wiring and heater supply are fine