Circuit Description
The 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 in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the control circuit by a low side driver within the control module. The control module tests the resistance of the heater to determine if a degrade in the heater element is present.
If the ECM detects that the resistance of the H02S heater is out of range, a DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTCs:
| • | DTC P0030 HO2S Heater Control Circuit Bank 1 Sensor 1 |
| • | DTC P0036 HO2S Heater Control Circuit Bank 1 Sensor 2 |
| • | DTC P0050 HO2S Heater Control Circuit Bank 2 Sensor 1 |
| • | DTC P0056 HO2S Heater Control Circuit Bank 2 Sensor 2 |
Conditions for Running the DTC
| • | The engine is running. |
| • | The filtered engine load is between 10-80 kg/h. |
| • | The commanded state of the H02S heater is between 2-98 percent. |
| • | The ignition 1 voltage is between 11-16 volts. |
| • | The modeled catalyst temperature is between 350-900°C (662-1,652°F). |
| • | The DTCs run continuously once the above conditions are met. |
Conditions for Setting the DTC
The ECM detects one of the following conditions:
| • | For H02S Bank 1 Sensor 1 or HO2S Bank 2 Sensor 1, the resistance is less than 4 ohms or more than 17.4-42.5 ohms depending on engine speed for more than 16 seconds. |
| • | For H02S Bank 1 Sensor 2 or HO2S Bank 2 Sensor 2, the resistance is less than 6 ohms or more than 20-45 ohms depending on engine speed for more than 16 seconds. |
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 Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |
2 |
Important: It may take up to 8 minutes for this DTC to set. Did DTC P0030, P0036, P0050, or P0056 fail this ignition? | -- | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 |
Is the resistance less than the specified value? | 3 ohms | Go to Step 5 | Go to Step 9 |
Important: Use the J 35616-200 Test Lamp Kit for this test. If the J 35616-200 is not available, use a test lamp that measures between 25-30 ohms. Is the voltage less than the specified value? | 0.3 V | Go to Step 7 | Go to Step 6 | |
6 | Test the control circuit of the HO2S heater for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 |
7 | Test for shorted terminals and poor connections at the HO2S. 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 12 | Go to Step 10 |
8 | Test for shorted terminals and poor connections at the engine control module (ECM). 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 12 | Go to Step 11 | |
9 | Repair the high resistance in the ignition 1 voltage circuit of the HO2S heater. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 12 | -- |
10 | Replace the appropriate HO2S. Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
