P0136
DTC P0136CIRCUIT 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 powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM 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. A high HO2S voltage output indicates a rich fuel mixture. A 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.
This diagnostic runs once per ignition cycle. This diagnostic has two phases for running the DTC, a passive test and an intrusive test. If the HO2S 2 voltage transitions below 286 mV and above 703 mV during the passive test, the DTC will pass for this ignition cycle. If the DTC does not pass during the passive test and too much time has elapsed since startup, the intrusive test will begin. The control module will adjust the air-to-fuel ratio during the intrusive test. As the air-to-fuel ratio is adjusted to rich and lean, the control module waits for a predicted response from the HO2S 2. If the HO2S 2 voltage transitions below 286 mV and above 703 mV, the diagnostic will pass for this ignition cycle. If the control module does not receive the expected response from the HO2S 2, DTC P0136 will set.
Each HO2S 1 has the following circuits:
- An HO2S 2 high signal circuit
- An HO2S 2 low signal circuit
- An HO2S 2 heater ignition voltage circuit
- An HO2S 2 heater low control circuit
- An HO2S low reference circuit
CONDITIONS FOR RUNNING THE DTC
DTCs P0036, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1134 are not set.
Passive Test
- The engine is running.
- The engine run time is less than 6.5 minutes.
Intrusive Test
- The Engine Run Time parameter is more than 6.5 minutes.
- The evaporative emission (EVAP) purge diagnostic is not active.
- The Engine Speed parameter is between 1,000-3,000RPM.
- The MAF Sensor parameter is between 13-55 g/s.
- The Vehicle Speed Sensor parameter is between 32-128 km/h (20-80 mph).
- The ignition voltage is between 9-18 volts.
- The above conditions have been met for 2.5 seconds.
CONDITIONS FOR SETTING THE DTC
The HO2S 2 is between 286-703 mV during the passive test.
One of the following tests fail:
Lean Intrusive Test
- The PCM detects that the HO2S 2 voltage is more than 286 mV for 14 seconds.
- The PCM detects that the HO2S 1 voltage is less than 100mV.
Rich Intrusive Test
- The PCM detects that the HO2S 2 voltage is less than 703 mV for 14 seconds.
- The PCM detects that the HO2S 1 voltage is more than 777 mV.
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
