Code 13 - O2 Sensor (Open Circuit): Notes

The ECM supplies .45 volt between terminals D6 and D7. When oxygen sensor reaches operating temperature, it varies this voltage from approximately one volt (rich exhaust) to approximately .10 volt (lean exhaust). Oxygen sensor produces no voltage when temperature is less than 600°F (360°C) and engine operates in open loop.

1. Code 13 will set if engine is at normal operating temperature and engine has been running at least 2 minutes. The oxygen signal voltage must be steady between .35 and .55 volt, and throttle position sensor signal is greater than 5 percent (about .3 volt more than closed throttle). All conditions must be met for approximately 60 seconds. If conditions for a Code 13 exist, system will not go into closed loop. An open sensor circuit or cold sensor causes open loop operation.
2. This determines if sensor, wiring or ECM is the cause of Code 13.
3. Use only a high impedance (10-megohm) digital volt-ohmmeter. This checks continuity of circuits No. D6 and D7. If circuit No. D6 is open, ECM voltage on circuit No. D7 will be greater than .6 volt.