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.
DTC Description
The ECM monitors the rich-lean switching time of the rear heated oxygen sensor (HO2S) after fuel cut-off, in order to validate dynamic behavior of rear heated oxygen sensor (HO2S). After detection of a fuel cut-off engine operating state, the ECM measures the rich-lean switching time of the rear heated oxygen sensor (HO2S) signal, and compares it to the predetermined limit value. DTC P0139 is set when the switching time exceeds the limit value.
NO RELATED
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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.