Code P0134, Heated Oxygen Sensor Open Circuit: Notes

The PCM supplies and monitors voltage of about .45 volt between PCM HO2S low reference circuit (Tan wire) and HO2S signal circuit (Purple wire). If read with a 10 megohm DVOM, voltage may read as low as .32 volt. HO2S varies voltage within a range of about 1 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than about 600°F (360°C). Open loop operation is caused by open oxygen sensor circuit or a cold sensor. Code P0134 will cause system to operate in open loop. PCM will illuminate Malfunction Indicator Light (MIL).

1. If conditions necessary to set Code P0132 exist, system will not go into closed loop.
2. This will determine if sensor or wiring is cause of Code P0134.
3. This test checks continuity in reference circuit.