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

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2009 Mercury Mountaineer, 2009 Mercury Milan, 2009 Mercury Mariner, 2009 Mercury Grand Marquis, and 2009 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 Short to VPWR in the harness or HO2S Water in the harness connector Open VPWR circuit Open UO2SHTR circuit Open GND circuit Low battery voltage Corrosion or poor mating terminals and wiring 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
E-Series 4.6L, E-Series 5.4L, Expedition, F-150, Flex, MKS, Navigator, Sable PZEV, Taurus PZEV, Taurus X PZEV	GO to Pinpoint Test DZ .
All others	GO to Pinpoint Test DW .