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.
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HOMESERVICE MANUALSFORD2009FUSION SEL, 3.0 1, FWDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - POWERTRAIN DTC CHARTS & DESCRIPTIONS (EXCEPT DIESEL & HYBRID)DTC DIAGNOSISDTC P0139: - O2 CIRCUIT SLOW RESPONSE (BANK 1, SENSOR 2)
2009 Ford Fusion SEL, 3.0 1, FWD
DTC P0139: - O2 Circuit Slow Response (Bank 1, Sensor 2)
2009 Ford Fusion SEL, 3.0 1, FWDSECTION DTC P0139: - O2 Circuit Slow Response (Bank 1, Sensor 2)
DTC P0139: - O2 CIRCUIT SLOW RESPONSE (BANK 1, SENSOR 2)
| Description: | The heated oxygen sensor (HO2S) monitor tracks the rate of voltage change during the rise and fall of the HO2S signal. When the rate of voltage change is less than a calibrated value, the powertrain control module (PCM) begins to modify the fuel trim attempting to increase the HO2S voltage switch rate. The DTC sets when the PCM is at the allowable limit or has exceeded an allowable length of time for fuel trim modification, without detecting an acceptable rate of voltage change. | ||
| Possible Causes: |
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| Diagnostic Aids: | Access the HO2S test results from the generic OBD menu to verify the DTC. | ||
| Application | Key On Engine Off | Key On Engine Running | Continuous Memory |
| All | - | - | GO to Pinpoint Test DW . |
RENDER: 1.0x
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.