Code 13, Open Oxygen Sensor Circuit: Notes

WARNING: This page is about a different car, the 1990 Chevrolet Corsica, 1990 Chevrolet Cavalier, and 1990 Chevrolet Beretta. However, it is still accessible from the selected car via links, so may be relevant.

The O2 sensor is like an open circuit and produces no voltage when its temperature is less than about 600°F (316°C). An open sensor circuit or cold sensor causes "open loop" operation.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Code 13 will set at normal operating temperature if at least 2 minutes have passed since engine start, O2 signal voltage is steady between .35-.55 volt and throttle position sensor signal is greater than 7 percent (1200 RPM). All conditions must be met for a precalibrated period of time.
This test determines if the O2 sensor, ECM or wiring is at fault.
Use only a high-impedance DVOM for this test. This checks for continuity in signal and ground circuits. If ground circuit is open, voltage on signal circuit will be greater than .6 volt.