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 (All Engines)
Code 13 will set with engine at operating temperature at least 2 minutes after engine start. The ECM must see: O2 signal voltage steady, between .35-.55 volt for more than 1 minute, or see TPS signal at more than 6% (.8-1.2 volt). Possible causes of a Code 13 are a faulty O2 sensor, faulty wiring or terminals, or a faulty ECM.
- This test allows the ECM to confirm either open or closed loop operation using the "SERVICE ENGINE SOON" light.
- This step verifies that no additional codes are stored and that Code 13 is intermittent.
- This test simulates a lean exhaust. If the ECM and wiring are okay, the ECM will turn the "SERVICE ENGINE SOON" light off. Light will flash open loop at least 30 seconds after engine start. It is normal for the light to remain off for a longer period of time after engine start.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra 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.