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Home >> Ford >> 2000 >> Contour SE, 2.5 L, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 2090 (Engine Controls - Powertrain DTC Charts And Descriptions (Except Diesel & Hybrid)) >> DTC Diagnosis >> P0139 - O2 Circuit Slow Response (Bank 1, Sensor 2)

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 2008 Mercury Sable, 2008 Mercury Mountaineer, 2008 Mercury Milan, 2008 Mercury Mariner, and 2008 Mercury Grand Marquis. 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: 
  • Contaminated or damaged HO2S
  • Deteriorating HO2S
  • Exhaust leaks
  • Aftermarket accessories
  • Performance modifications
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 .
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