Code 13 - Open O2 Circuit (A/J/N/P Body): Notes

The ECM supplies voltage of about .45 volts between terminals "B2" and "B23". (If measured with a 10-megohm digital voltmeter, this may read as low as .32 volts). The O2 sensor varies the voltage within a range of about one volt (rich exhaust) to .1 volt (lean exhaust). The O2 sensor is like an open circuit and produces no voltage when it is below about 600°F (316°C). An open sensor circuit or cold sensor causes open loop operation.

Code 13 will set if at least 40 seconds have passed since engine start, O2 signal voltage is steady between .35 and .55 volt for more than one minute and throttle potion sensor signal is above 7 percent (1200 RPM). All conditions must be met for at least 3 seconds.

1. Connecting the "Scan" tester with engine running allows the ECM to confirm either open or closed loop operation.
2. Determines if the O2 sensor, ECM or wiring is at fault.
3. Use only a high impedance digital volt ohm meter for this test. This test checks for continuity in circuits No. 412 and 413.