Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Code 13, Heated Oxygen Sensor Circuit, Open Circuit: Notes
Heated Oxygen (O2) sensor produces a voltage that varies within a range of about 0.1 volt (lean exhaust) to 1.0 volt (rich exhaust). O2 sensor has a built-in heater that keeps O2 sensor at operating temperature while engine is running. O2 sensor is like an open circuit and produces no voltage when sensor temperature is less than 600°F (316°C), causing an open loop condition.
Code 13 will set if the following conditions are met for at least 30 seconds:
- Engine operating temperature is greater than 158°F (70°C).
- Engine running for at least 2 minutes.
- Engine speed is greater than 260 RPM.
- MAP sensor pressure is greater than 350 mm Hg of vacuum.
- Heated O2 sensor temperature less than 600°F (360°C).NOTE: Test numbers refer to test numbers on diagnostic chart.
- Checks for short to voltage in Yellow/Blue wire or a faulty ECM.
- Checks for short to ground in Yellow/Blue wire, a faulty ECM or a faulty O2 sensor.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.