Circuit Description
The heated oxygen sensor (HO2S) is a sensor used to detect oxygen content in the exhaust. The powertrain control module (PCM) supplies the sensor with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The sensor varies the voltage based on the oxygen content in the exhaust. When the exhaust stream is lean, indicating more oxygen, the sensor produces a low voltage signal. When the exhaust stream is rich, indicating less oxygen, the sensor produces a high voltage signal.
The PCM monitors the HO2S activity to make sure that enough lean to rich and rich to lean switches occur. A lean to rich switch occurs when the HO2S signal voltage changes from less than 300 mV to more than 600 mV. A rich to lean switch occurs when the HO2S signal voltage switches from more than 600 mV to less than 300 mV. The PCM counts the number of lean to rich and rich to lean switches for 100 seconds. This diagnostic trouble code (DTC) indicates that the HO2S did not switch enough times.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0130, P0131, P0135, P0150, P0151, P0171, P0175, P0202-P0208, P0401, P0403, P0404, P0405, P0410, P0418, P0419, P0560-P0563, P1106, P1107, P1111, P1112, P1404, P1415, or P1416 are not set. |
| • | The engine speed is between 1,200-2,800 RPM. |
| • | The mass air flow (MAF) is between 15-35 g/s. |
| • | The throttle position (TP) angle is more than 3 percent. |
| • | The system voltage is between 9-18 volts. |
| • | The coolant temperature is higher than 75°C (167°F). |
| • | The exhaust gas recirculation (EGR) flow diagnostic test is not active. |
| • | The Closed Loop fuel control is enabled. |
| • | The catalyst diagnostic test is not active. |
| • | The engine run time is more than 202 seconds. |
| • | The transmission is not in Park, Reverse, or Neutral. |
| • | The secondary air injection (AIR) diagnostic tests are not active. |
| • | The above conditions exist for 3 seconds. |
Conditions for Setting the DTC
| • | The PCM monitors fewer than 5 lean-to-rich switches, and fewer than 5 rich-to-lean switches. |
| • | The condition is present for a 90 second monitoring period. |
| • | The O2 voltage is between 325-625 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. |
Diagnostic Aids
Notice: Do not solder heated oxygen sensor wires. Soldering the wires will result in the loss of the air reference to the sensor. Refer to Engine Electrical for proper wire and connection repair techniques.
If the condition is intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests whether other possible causes of this DTC have already been diagnosed.
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Diagnose other DTCs first, because other DTCs may be the cause of this DTC setting.
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With the engine running warm and at fast idle, and with the coolant at least 85°C (185°F) , the oxygen sensor voltage should rapidly swing above 600 mV and below 300 mV.
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This step tests if the oxygen sensor voltage is swinging between rich and lean very slowly, or not at all.
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This step tests for causes of oxygen sensor failure. If the sensor is replaced without finding the cause of contamination, premature failure of the new sensor may result.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||
Were you sent here from another DTC? | -- | Go to Step 4 | Go to Step 3 | |||||||||
Are any other DTCs set? | -- | Go to Step 4 | ||||||||||
Does the HO2S voltage rapidly swing above and below the range specified? | 325-625 mV | Go to Step 5 | Go to Step 6 | |||||||||
5 | With engine running at 2,000 RPM, observe the scan tool display Loop Status. Does the display indicate Closed? | -- | Go to Intermittent Conditions | Go to Step 9 | ||||||||
Does the HO2S voltage remain between the specified values longer than it swings outside this range? | 325-625 mV | Go to Step 9 | Go to Step 7 | |||||||||
7 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 | ||||||||
8 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||||
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Important: Before replacing the oxygen sensor, the cause of contamination must be found and corrected. Test for the following items:
Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 , or refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 10 | -- | |||||||||
10 |
Does the DTC run and pass? | -- | Go to Step 11 | Go to Step 2 | ||||||||
11 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||
