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 MANUALSFORD2005TAURUS SEL, 4D SEDANREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 670 (ENGINE CONTROLS - POWERTRAIN DTC CHARTS AND DESCRIPTIONS (EXCEPT DIESEL & HYBRID))DTC DIAGNOSISP0139 - O2 CIRCUIT SLOW RESPONSE (BANK 1, SENSOR 2)
2005 Ford Taurus SEL, 4D Sedan
P0139 - O2 Circuit Slow Response (Bank 1, Sensor 2)
2005 Ford Taurus SEL, 4D SedanSECTION P0139 - O2 Circuit Slow Response (Bank 1, Sensor 2)
WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2007 Mercury Mountaineer, 2007 Mercury Monterey, 2007 Mercury Montego, 2007 Mercury Milan, and 2007 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.
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 is set 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 | - | - | refer to PINPOINT TEST DW . | |
RENDER: 1.0x
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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.