Diagnostic Trouble Code (DTC) P0135 Front Heated Oxygen Sensor Heater Circuit Not Functioning

Diagnostic Trouble Code (DTC) P0135

Front Heated Oxygen Sensor Heater Circuit Not Functioning




Features of the Circuit


  • This circuit utilizes heated oxygen sensors (HO2S) for controlling fuel and post catalyst supervising.
  • All the HO2S present here match the oxygen percentage of the atmospheric air with the oxygen content present in the exhaust stream.
  • In order to supply flawless voltage signal, the HO2S should gain the requisite operating temperature.
  • The time needed for the sensor to reach the operating temperature is reduced by a heating element inside the HO2S.
  • The ignition 1 voltage circuit provides voltage to the heater through a fuse.
  • Ground is provided to the heater by the HO2S heater low control circuit if the engine is ON, through a low side driver within the ECM.
  • The ECM regulates the flow of current through the heater for the convenience of diagnosis.
  • If there is any discrepancy regarding the mentioned parameters in the HO2S heater current identified by the ECM then DTC P0135 is boosted immediately.



Time for setting the DTC

Task boosted after DTC sets

When will DTC clear?

1) Engine running time is > 30 seconds.

1) The Malfunction Indicator Lamp (MIL) will be seen glowing after three failed repetitive trips.


1) The MIL will go off after three repetitive ignition cycles in which the diagnostic runs perfectly

2) Filtered O2 heater current is < 0.1 amps

2) The ECM will begin to record operating conditions at the time when the diagnostic fails which will be stored in the Freeze Frame.


2) A history DTC will clear by itself after 40 successive warm-up cycles flawlessly

3) When DTCs P0106, P0117, P0118, P1017 are not set

3) Failure Records will


3) The scan tool can be used to remove all existing DTCs.



4) A history Diagnostic Trouble Code (DTC) will be stored.






Diagnostic Tool Available:


  • An intermittent can be created by a) rubbed through wire insulation or b)a wire contacting the exhaust.
  • You are required to check for a)  poor connection or b) damaged harness –
  • Examine all  harness connectors for the following conditions:
  1. Broken locks
  2. Improperly formed or
  3. Tampered  Terminals
  4. Poor terminal-to-wire connection
  5. Damaged harness
  6. Inaccurate mating

Guide to carry out the test check:

Number(s) below mean the step number(s) on the Diagnostic Table.

  1. The EOBD System Check helps the technician to execute some basic checks and store the freeze frame and failure records data on the scan tool if necessary. This creates an automatic electronic copy of the data recorded when the malfunction occurred. This reading is then stored on the scan tool for future reference.
  1. This step ensures that DTC P0135 is the resultant of a hard failure or an intermittent condition. If the ignition is ON with the engine OFF then the HO2S1 voltage highlighted on the scan tool should change rapidly within several minutes ranging between  0 or 1 volt, assuring that the heater is functioning desirably.
  1. Examining the terminal 2 of the HO2S1 connector testifies whether any voltage is available to the HO2S1 heater.
  1. If voltage supply is affirmed at the connector, then it becomes an ideal voltage source to check for a ground at terminal 3.
  1. This determines that voltage is not available at the HO2S1 because of an open in the HO2S1 fuse or open ignition feed circuit. If the fuse remains open, inspect whether it was because of a short in the ignition feed circuit before substituting  the fuse.