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, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0401, P0404, P0405, P0440, P0442, P0446, P0452, P0453, P1404, or P1441 are not set. |
| • | The engine run time is more than 409 seconds. |
| • | The ignition 1 signal is between 9-18 volts. |
| • | Intrusive tests are not in progress. |
| • | Scan tool output controls are not active. |
Conditions for Setting the DTC
The HO2S signal voltage is steady between 350-550 mV for 60 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 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. |
| • | The control module commands open loop. |
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 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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After the ignition is turned ON, the HO2S heater heats up causing the HO2S signal voltage to either increase or decrease. This indicates that the HO2S heater is OK.
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If the HO2S voltage is varying outside the specified range, the condition is not present.
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If the voltage is below the specified value, the high signal circuit, the low signal circuit, and the PCM are OK.
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If the voltage is above the specified value, the low signal circuit is OK.
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All oxygen sensors must be disconnected to isolate a short to ground in the HO2S heater ignition 1 voltage circuit.
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Resistance within the specified range indicates the HO2S heater is OK.
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: Allow the engine to cool for one-half hour before proceeding with this diagnostic. This allows the HO2S signal voltage to return to bias voltage, approximately 447 mV.
Does the HO2S voltage go from bias voltage to more than or less than the specified range? | 300-600 mV | Go to Step 3 | Go to Step 5 | |
Is the HO2S voltage varying outside the specified range? | 350-550 mV | Go to Step 4 | Go to Step 5 | |
4 |
Does the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions |
Is the HO2S voltage less than the specified value? | 200 mV | Go to Step 9 | Go to Step 6 | |
Is the voltage above the specified value? | 4.5 V | Go to Step 7 | Go to Step 8 | |
7 |
Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 16 |
8 |
Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 16 |
9 | Remove the jumpers from the previous step. Is the ENG 1 fuse open? | -- | Go to Step 12 | Go to Step 10 |
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 17 |
11 |
Does the test lamp illuminate? | -- | Go to Step 15 | Go to Step 18 |
Did you find and correct a short to ground in the ignition 1 voltage circuit? | -- | Go to Step 21 | Go to Step 13 | |
13 |
Important: Perform the following test on all oxygen sensors. A condition in any sensor will cause this DTC to set. Test the HO2S ignition 1 voltage circuit, sensor side, for a short to the HO2S body. Refer to Circuit Testing in Wiring Systems. Did you find the condition? | -- | Go to Step 19 | Go to Step 14 |
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Important: Perform the following test on all oxygen sensors. A condition in any sensor will cause this DTC to set. Measure the resistance between the HO2S ignition 1 voltage circuit, sensor side, and the HO2S heater ground circuit, sensor side. Refer to Circuit Testing in Wiring Systems. Does the resistance of any sensor measure above or below the specified range? | 2-50 ohms | Go to Step 19 | Go to Intermittent Conditions | |
15 | Inspect for poor connections at the harness connector of the affected 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 19 | |
16 | Inspect for poor connections at the harness connector of the 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 21 | Go to Step 20 |
17 | Repair the open in the ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
18 | Repair the open in the HO2S heater ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | -- | |
19 | 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 21 | -- |
20 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
21 |
Does the DTC run and pass? | -- | Go to Step 22 | Go to Step 2 |
22 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
