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DTC P0135: O2 Heater Circuit (Bank 1, Sensor 1)

WARNING: This page does not describe the selected car, but rather 33 other vehicles, including the 2010 Mercury Mountaineer, 2010 Mercury Milan, 2010 Mercury Mariner, 2010 Mercury Grand Marquis, and 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0135: O2 HEATER CIRCUIT (BANK 1, SENSOR 1)

Description:  During testing the heated oxygen sensor (HO2S) heaters are checked for open and short circuits and excessive current draw. The test fails when the current draw exceeds a calibrated limit or an open or short circuit is detected.
Possible Causes: 
  • Vacuum hose disconnected on exhaust gas recirculation (EGR) system module (ESM) applications
  • UO2SHTR circuit short to voltage
  • Water in the harness connector
  • Open VPWR circuit
  • Open UO2SHTR circuit
  • Open GND circuit
  • Low battery voltage
  • Corrosion
  • Poor connections
  • Damaged HO2S heater
Diagnostic Aids:  Inspect the connectors for signs of damage, water ingress, or corrosion.
Application  Key On Engine Off  Key On Engine Running  Continuous Memory 
Escape/Mariner 3.0L,
E-Series 4.6L,
E-Series 5.4L,
Expedition,
F-150,
Flex,
Fusion 3.0L,
Milan 3.0L,
MKS,
MKT,
Navigator,
Taurus		 GO to PINPOINT TEST DZ .
All others GO to PINPOINT TEST DW .
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