P0136

DTC P0136

CIRCUIT DESCRIPTION
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the engine control module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The ECM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. High HO2S voltage output indicates a rich fuel mixture; low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. If the ECM detects an active HO2S voltage signal below a calibrated minimum amplitude, DTCs P0130, P0136, P0150, or P0156 will set.

Each HO2S has the following circuits:
- The HO2S high signal circuit
- The HO2S low signal circuit
- The HO2S heater ignition 1 voltage circuit
- The HO2S heater low control circuit

CONDITIONS FOR RUNNING THE DTC
- DTCs P0443, P0444, or P0445 are not set.
- The engine is running.
- The Calc Convertor Temp parameter is less than 800�C (1,472�F).
- The MAF parameter is between 10-35 g/s.
- The TP Angle parameter is between 5-35 percent.
- The Battery Voltage parameter is more than 10.5 volts.

CONDITIONS FOR SETTING THE DTC
- The ECM detects that the affected HO2S 1 voltage is between 60-400 mV, when the same bank HO2S 2 voltage is above 499 mV for at least 10 seconds.

OR

- The ECM detects that the affected HO2S 1 voltage is 600-1080 mV, when the same bank HO2S 2 voltage is below 104 mV for at least 10 seconds.

OR

- The ECM detects that the affected HO2S 1 voltage has risen 16 times out of 24 samples when the heater is cycled OFF.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

TEST

Steps 1-3:

Steps 4-5:

Step 6:

Steps 7-12: