Code P0134, Heated Oxygen Sensor Open Circuit: Notes

WARNING: This page is about a different car, the 1994 Oldsmobile Ninety-Eight and 1994 Buick Park Avenue. However, it is still accessible from the selected car via links, so may be relevant.

The PCM supplies and monitors voltage of approximately .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 approximately 1 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than approximately 600°F (360°C). Open loop operation is caused by open oxygen sensor circuit or a cold sensor. Code P0134 will set when the following conditions are present.

Engine coolant temperature is greater than 110°F (43°C).
Engine run time is more than 40 seconds.
HO2S signal voltage is steady between .35-.56 volt.
Throttle angle is greater than 3 percent.
All conditions are met for approximately 30 or more seconds.

Code P0134 will cause system to operate in open loop. PCM will illuminate Malfunction Indicator Light (MIL).

NOTE: Test numbers refer to numbers on diagnostic chart.

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