P0135 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

The HO2S-11 heater circuit is monitored by the Powertrain Control Module (PCM). The test fails when improper current amperage is drawn through the front HO2S heater from the PCM.

Possible Causes:
- The front HO2S heater circuit is open
- The front HO2S heater circuit is shorted to VPWR
- The front HO2S heater circuit is shorted to GND
- The front HO2S heater

Diagnostic Aids:
The front HO2S heater resistance should be 2.3-4.3 ohms at 25°C (77°F).