Code 13, Oxygen Sensor Circuit Open Circuit
The ECM supplies approximately .45 volt between ECM terminals 3 and 20. If reading is taken with a 10-megohm DVOM, reading may be as low as .32 volt. The O2 sensor produces a varying voltage as engine reaches normal operating temperature. Voltage will vary from .10-1.0 volt. The O2 sensor does not produce a voltage until sensor reaches 600°F (316°C). When sensor is less than this temperature, an "Open Loop" condition exists. Code 13 will set with engine at normal operating temperature, at least 5 minutes of engine run time after engine start and part throttle, O2 sensor signal steady between .35-.55 volt, throttle is off idle and all conditions present for approximately 60 seconds. Computer system will not go into "Closed Loop" when these conditions exist.
- This determines if O2 sensor is at fault or if ECM and wiring are faulty.