The ECM supplies .45 volt between terminals No. B2 and B3. When oxygen sensor reaches operating temperature, it varies this voltage from approximately one volt (rich exhaust) to approximately .10 volt (lean exhaust). Oxygen sensor has a heater incorporated as part of sensor. Heater is used to heat up sensor, causing sensor to produce voltage signal sooner. Heater portion of sensor will not effect Code 13. Oxygen sensor produces no voltage when temperature is less than 572°F (300°C). An open sensor circuit or cold sensor causes open loop operation.

NOTE: Test numbers refer to numbers on diagnostic chart.

Code 13 will set if engine is at normal operating temperature and engine has been running at least 3 minutes. The oxygen signal voltage must be steady between .35 and .55 volts, throttle position sensor signal is greater than 10 percent, and no Code 21 or 31 is set. All conditions must be met for approximately 40 seconds. If conditions for a Code 13 exist, system will not go into closed loop.
This determines if sensor, wiring or ECM is the cause of Code 13.
Use only a high impedance (10-megohm) digital volt/ohmmeter. This checks continuity of circuits No. B2 and B3. If circuit No. B2 is open, ECM voltage on circuit No. B3 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 - O2 Sensor (Open Circuit): Notes

Use the Manual With the Right Hardware

When to See a Mechanic

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