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DTC P0136: HO2S Circuit Malfunction (HO2S-12)

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2005 Mercury Sable, 2005 Mercury Mountaineer, 2005 Mercury Monterey, 2005 Mercury Montego, and 2005 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.
P0136 - HO2S CIRCUIT MALFUNCTION (HO2S-12)

Description:  The downstream heated oxygen sensors (HO2S) are continuously checked for maximum and minimum voltages. The test fails when the voltages fail to meet the calibrated limits.
Possible Causes: 
  • Pinched, shorted, and corroded wiring and pins
  • Crossed sensor wires
  • Exhaust leaks
  • Contaminated or damaged sensor
Diagnostic Aids:   
Application  Key On Engine Off  Key On Engine Running  Continuous Memory 
All - - GO to H: Fuel Control STEP H49.