Circuit Description
The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.
The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect the voltage went out of the bias range, a diagnostic trouble code (DTC) sets.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0300, P0351, P0401, P0404, P0405, P0440, P0442, P0446, P0452, P0453, P1258, P1404, P1441 are not set. |
| • | The engine run time is more than 409 seconds. |
| • | The ignition 1 signal is between 9 volts and 18 volts. |
Conditions for Setting the DTC
| • | The HO2S signal voltage is steady between 350 mV and 550 mV. |
| • | The conditions are present for 57 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. |
Diagnostic Aids
Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
| • | An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems. |
| • | An HO2S that is loose causes this DTC to set. |
For an intermittent condition, refer to Symptoms - Engine Controls .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The engine must be at the normal operating temperature before you perform this test.
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Using the Freeze Frame/Failure Records may help to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records can help determine how many miles since the DTC set. You can also use the Fail Counter and the Pass Counter in order to determine the number of ignition cycles in which the diagnostic reported a pass or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions that the PCM recorded. These conditions include:
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If the scan tool indicates the HO2S voltage goes below 200 mV, the HO2S circuits and the PCM are OK.
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This step tests whether the low signal circuit from the PCM is OK. A voltage indicates the PCM and the wiring are OK.
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This step tests whether the signal circuit from the PCM is OK.
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Disconnecting the PCM allows using the DMM in order to test the circuit continuity. This procedure helps to locate a circuit that is open or shorted.
| • | The RPM |
| • | The vehicle load |
| • | The vehicle speed |
| • | The temperature |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
|
Important: Inspect the HO2S for being secure before proceeding with this DTC. A loose sensor could cause this DTC to set.
Does the scan tool indicate the HO2S voltage varying outside the specified range? | 350-550 mV | Go to Step 3 | Go to Step 4 | |
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | |
Is the HO2S voltage below the specified value? | 200 mV | Go to Step 8 | Go to Step 5 | |
Does the DMM indicate that the voltage is near the specified value? | 5 V | Go to Step 6 | Go to Step 7 | |
Did you find and correct the HO2S high circuit condition? | -- | Go to Step 12 | Go to Step 10 | |
Did you find and correct the HO2S low signal circuit condition? | -- | Go to Step 12 | Go to Step 10 | |
8 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
9 | Replace the appropriate HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the action? | -- | -- | |
10 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 |
13 | With a scan tool observe the Stored information, Capture info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
