The ECM supplies a voltage of about .45 volt between terminals D7 and D6. If measured with 10-megohm voltmeter, meter indication may be as low as .32 volt.

Oxygen sensor varies voltage within range of approximately .1 volt (lean exhaust) to 1.0 volt (rich exhaust). The sensor produces no voltage when sensor temperature is less than 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 if the following conditions occur:
- Code 21 or 22 is not detected.
- Engine is at normal operating temperature.
- There is at least one minute of engine run time.
- Oxygen signal is steady between .35-.55 volt.
- Throttle angle is more than 7 percent.
- All conditions are met for one minute.
If conditions for Code 13 exist, system will not go to closed loop operation.
This test determines whether the oxygen sensor is the problem, or the ECM and wiring are at fault.
When performing this test, use only a high impedance digital volt-ohmmeter. This test checks the continuity of O2 ground circuit and O2 signal circuit. If O2 ground wire is open, ECM voltage on the O2 signal wire 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 Sensor Circuit: Notes

Use the Manual With the Right Hardware

When to See a Mechanic