Code 13 - Oxygen Sensor (Open Circuit): Notes

The ECM supplies .45 volt between terminals B2 and B3. When oxygen sensor reaches operating temperature, it varies this voltage from about one volt (rich exhaust) to about .10 volt (lean exhaust). A heater, incorporated in oxygen sensor, is used to heat sensor, causing sensor to produce voltage signal sooner. Heater portion of sensor will not affect Code 13. Oxygen sensor produces no voltage when temperature is less than 572°F (300°C). An open sensor circuit or cold sensor causes open loop operation.

1. Code 13 will set under following conditions: engine is at normal operating temperature, engine has been running at least 3 minutes, oxygen signal voltage is steady between .35 and .55 volt, throttle position sensor signal is greater than 10 percent, and no Code 21 or 31 is set. All conditions must be met for about 40 seconds. If conditions for a Code 13 exist, system will not go into closed loop.
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. If circuit to terminal B2 is open, ECM voltage at B3 will be greater than .6 volt.