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, Open Oxygen Sensor Circuit: Notes
Code 13 will set 2 minutes after engine start if the ECM receives a steady O2 signal voltage between .35-.55 volt for more than one minute, with TPS signal at more than 6.5 percent. Engine must also be at normal operating temperature. Possible causes of a Code 13 are a faulty O2 sensor, faulty wiring or terminals, or a faulty ECM.
- Code 13 will set if engine is at operating temperature, O2 signal voltage is steady between .35 and .55 volt, throttle angle is greater than 6.5 percent and all conditions have been met for about 60 seconds. If the conditions for Code 13 exist, the system will not go into "closed loop".
- This test will determine if the sensor is at fault, or if the wiring to the ECM is the cause of Code 13.
- Use only a high impedence (10-megohm) digital volt/ohmmeter when doing this test. 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 (600 mv).
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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.
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