Circuit Description
Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature and provide an accurate voltage signal. A low side driver within the engine control module (ECM) is pulse width controlled to provide current to the heater elements. The ECM will not allow continuous HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The ECM continuously monitors the HO2S operating state by briefly turning OFF the heater low side driver at regular intervals. A small reference voltage of approximately 4.5 volts is present at the heater low control circuit. When the low side driver is commanded ON the reference voltage is low, and when the low side driver is commanded ON the reference voltage is high, close to battery voltage. If the ECM detects that the HO2S heater low control circuit voltage is between 2.6-4.6 volts when the heater is commanded ON, the following DTCs will set:
| • | DTC P0030 for HO2S bank 1 sensor 1 |
| • | DTC P0036 for HO2S bank 1 sensor 2 |
| • | DTC P0050 for HO2S bank 2 sensor 1 |
| • | DTC P0056 for HO2S bank 2 sensor 2 |
Conditions for Running the DTC
| • | The engine is running |
| • | The Ignition 1 Signal parameter is more than 10 volts. |
Conditions for Setting the DTC
The ECM detects that the HO2S heater low control circuit voltage is between 2.6-4.6 volts when the heater is commanded ON, indicating an open HO2S heater circuit.
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 | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module 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 |
Does the DTC 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 | Inspect the appropriate heated oxygen sensor (HO2S) ignition 1 voltage fuse for an open. Is the fuse open? | Go to Step 7 | Go to Step 5 |
5 |
Important: Use a known good ground. DO NOT use the HO2S heater low control circuit, the HO2S low reference circuit, or the HO2S low signal circuit. Does the test lamp illuminate? | Go to Step 6 | Go to Step 12 |
6 |
Important: The test lamp may flash OFF and ON as the ECM cycles the heater control circuit.
Does the test lamp illuminate? | Go to Step 10 | Go to Step 9 |
7 | Test the affected HO2S ignition 1 voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 8 |
8 |
Important: Perform the following test on all HO2S' which are supplied voltage by the suspect circuit. Test the ignition 1 voltage circuit on the sensor side of the HO2S connector for a short to ground. Refer to Circuit Testing in Wiring Systems. Is any sensor shorted to ground? | Go to Step 13 | Go to Intermittent Conditions |
9 | Test the affected HO2S heater low control 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 15 | Go to Step 11 |
10 | Test for an intermittent and poor connections at the HO2S. 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 15 | Go to Step 13 |
11 | Test for an intermittent 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 15 | Go to Step 14 |
12 | Repair the open or high resistance in the affected HO2S heater ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | -- |
13 | Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 , Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 , Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 , or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 . Did you complete the replacement? | Go to Step 15 | -- |
14 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | Go to Step 15 | -- |
15 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 16 |
16 | 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 |
