Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements within each HO2S heat the sensor. This allows the system to enter Closed Loop earlier and the control module to calculate air-to-fuel ratio quicker.
The HO2S 2 is used for catalyst monitoring. This diagnostic runs once per ignition cycle. This diagnostic has 2 phases for running the DTC, a passive test and an intrusive test. If the HO2S 2 voltage transitions below 299 mV and above 721 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/or lean, the control module waits for a predicted response from the HO2S 2. If the HO2S 2 voltage transitions below 299 mV and/or above 721 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0136 HO2S Circuit Bank 1 Sensor 2
Conditions for Running the DTC
DTCs P0030, P0050, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0150, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0201-P0208, P0442, P0443, P0446, P0449, P0455 are not set.
Passive Test
| • | The engine is running. |
| • | The engine run time is less than 19 minutes and 50 seconds. |
Intrusive Test
| • | The Engine Run Time parameter is more than 2 seconds. |
| • | The ignition voltage is between 10-18 volts. |
| • | The Engine Speed parameter is between 100-3,000 RPM. |
| • | The MAF Sensor parameter is between 8-30 g/s. |
| • | The Vehicle Speed parameter is between 24-145 km/h (15-91 mph). |
| • | The Loop Status parameter is Closed. |
| • | The Air Fuel Ratio parameter is between 13.2-16.2:1. |
| • | The evaporative emission (EVAP) purge is not active. |
| • | DTC P0136 runs once per key cycle once the above conditions are met. |
Conditions for Setting the DTC
| • | The powertrain control module (PCM) detects that the HO2S 2 did not transition below 299 mV or above 721 mV during the passive test for 20 minutes. |
| • | One of the following tests fail: |
Lean Intrusive Test
| - | The PCM detects that the HO2S 2 is more than 299 mV for 15 seconds. |
| - | The HO2S Bank 1 Sensor 1 and HO2S Bank 2 Sensor 1 is less than 300 mV. |
Rich Intrusive Test
| - | The PCM detects that the HO2S 2 is less than 721 mV for 15 seconds. |
| - | The HO2S Bank 1 Sensor 1 and HO2S Bank 2 Sensor 1 are more than 600 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. |
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views and Engine Controls Connector End Views | ||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||||
2 |
Did the voltage parameter vary above and below the specified range? | 299-721 mV | Go to Step 3 | Go to Step 4 | ||||||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||||||||
4 |
Is the voltage more than the specified value? | 800 mV | Go to Step 9 | Go to Step 5 | ||||||||||||
5 | Is the voltage less than the specified value? | 75 mV | Go to Step 10 | Go to Step 6 | ||||||||||||
6 | Measure the voltage from the HO2S 2 low signal circuit, on the engine harness side, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage less than the specified value? | 100 mV | Go to Step 7 | Go to Step 11 | ||||||||||||
7 |
Is the voltage less than the specified value? | 15 mV | Go to Step 8 | Go to Step 12 | ||||||||||||
8 |
Is the voltage less than the specified value? | 15 mV | Go to Step 15 | Go to Step 13 | ||||||||||||
9 | Test the HO2S 2 high signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||||
10 | Test the HO2S 2 high signal circuit for a short to ground or a short to the HO2S 2 low signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||||
11 | Test the HO2S 2 low signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||||
12 | Test the HO2S 2 high signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||||
13 | Test the HO2S 2 low signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||||
14 | Test for poor connections and shorted terminals at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17 | ||||||||||||
15 | The HO2S 2 may be detecting a rich or lean exhaust condition. Check for one or more of the following conditions: Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||||||||||
16 | Test for poor connections and shorted terminals at the HO2S 2. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 | ||||||||||||
17 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 19 | -- | ||||||||||||
18 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the HO2S 2. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||||||||||
19 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 20 | ||||||||||||
20 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||||||
