Code 13, Open Oxygen Sensor Circuit: Notes

Fig 1: Code 13, Schematic - Open Oxygen Sensor Ckt

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

Code 13 will set if the following conditions occur:
- Engine at normal operating temperature.
- At least one minute engine time after start.
- Oxygen signal voltage steady between .35-.55 volt.
- Throttle angle more than 7 percent.
- All conditions must be met for about 60 seconds.
If conditions for a Code 13 exist, the system will not go into "closed loop".
This test determines if the oxygen sensor is the problem, or if the ECM and wiring are at fault.
When doing this test, use only a high impedence (10-megohm) digital volt/ohmmeter. This test checks the continuity of circuits No. 412 and 413. If circuit No. 413 is open, the ECM voltage on circuit No. 412 will be greater than .6 volt (600 mV).