The ECM supplies a voltage of about .45 volt between terminals "D6" and "D7". If measured with 10-megohm digital voltmeter, this may read as low as .32 volt. The oxygen sensor varies the voltage within a range of about one volt if the exhaust is rich, down through about .10 volts if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is less than 600°F (360°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 if the following conditions occur:
- Engine is at operating temperature.
- Up to 2 minutes engine running time after start.
- Oxygen signal steady between .35 and .55 volt.
- Throttle position sensor signal greater than idle.
- All conditions must be met for 60 seconds. If all conditions for a Code 13 exist, system will not go into "closed loop".
This test will determine if the sensor or the wiring is the cause of a Code 13.
When performing this test, use only a high impedance (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.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Code 13 - Open Oxygen (O2) Sensor Circuit: Notes

Use the Manual With the Right Hardware

When to See a Mechanic

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