ECM supplies approximately .45 volt between ECM terminals D6 and D7. If voltage is measured with a 10-megohm DVOM, reading may be as low as .32 volt. Heater circuit of heated Oxygen (O2) sensor is turned on when engine is running. Heated O2 sensor produces a varying voltage to ECM as engine reaches normal operating temperature. Voltage varies between .1 (lean) and 1.0 (rich) volt depending on conditions of exhaust gases in exhaust manifold.

Heated O2 sensor will not produce voltage until sensor reaches 600°F (316°C). When sensor is less than specified, open loop condition exists.

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

Code 13 will set if the following conditions are present for at least 40 seconds:
- Engine operating temperature is greater than 157°F (69.5°C).
- Engine has been running for at least 120 seconds after start.
- Heated O2 signal voltage is steady between .347 and .547 volt.
- Throttle angle is greater than 5 percent.
- Vehicle speed is greater than 3 MPH.
If conditions for Code 13 exist, system will not go into closed loop.
Determines if Heated O2 sensor, ECM and/or wiring is faulty.
Use only high impedance DVOM when performing this test. Checks continuity of terminals D6 and D7. If terminal D6 is open, ECM voltage on terminal D7 will be greater than .6 volt (600 mV).

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, Heated O2 Sensor Circuit, Open Circuit (VIN 8): Notes

Use the Manual With the Right Hardware

When to See a Mechanic

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