Circuit Description
The heated oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high. When the HO2S detects that the engine is operating lean, the signal voltage is low. This oscillation above and below the bias voltage, sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.
The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. The control module also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or "lean out" the mixture, when the HO2S detects a rich exhaust condition.
This DTC is designed to detect a HO2S that is lazy or slow when switching from lean to rich or from rich to lean. The DTC is set when the average transition time is too long.
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, or P1441 are not set. |
| • | The engine coolant temperature (ECT) sensor temperature is more than 57°C (135°F). |
| • | The engine run time is more than 160 seconds. |
| • | The mass air flow (MAF) sensor is between 15-55 g/s. |
| • | The engine speed is between 1,100-3,000 RPM. |
| • | The throttle position (TP) sensor is more than 5 percent. |
| • | The loop status is closed. |
| • | The ignition 1 signal is between 9-18 volts. |
| • | The fuel tank level remaining is more than 10 percent. |
| • | Intrusive tests are not in progress. |
| • | The scan tool output controls are not active. |
| • | The above conditions are met for 100 seconds. |
Conditions for Setting the DTC
The rich-to-lean and lean-to-rich average response time is more than a calibrated value.
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.
| • | This diagnostic only runs once per ignition cycle. |
| • | A malfunction in the HO2S heater circuits causes a DTC to set. Check the HO2S heater circuits for intermittent opens and for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and the connections for breaks or for contamination. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. |
| • | 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 to determine how many miles since the DTC set. The Fail Counter and the Pass Counter can also help determine how many ignition cycles 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, and refer to Symptoms - Engine Controls . |
| These conditions include: |
| • | The RPM |
| • | The vehicle load |
| • | The vehicle speed |
| • | The temperature |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the condition is present. This test may take minutes for the diagnostic to run.
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When DTCs P0133 and P0153 are set at the same time, fuel contamination is likely.
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An exhaust leak 152.4-304.8 mm (6-12 in) away from the HO2S can cause a DTC to set.
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This step tests whether a good ground circuit is available.
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This step tests the integrity of the HO2S high signal circuit to the PCM.
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This step tests the integrity of the HO2S high signal circuit to the PCM.
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Certain RTV silicone gasket materials release vapors that can contaminate the HO2S. Silicone in the fuel can also cause silicone contamination. If the sensors appear contaminated by silicone, and if all the silicone sealant is a non-silicone base, advise the customer to try a different fuel company. A missing fuel filler restrictor indicates that the customer may have used leaded fuel.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||
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Important: If any DTCs are set except P0133 or P0153, refer to those DTCs before proceeding with this diagnostic table.
Did DTC P0133 or P0153 fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | |||||||||
Did both DTC P0133 and P0153 fail this ignition? | -- | Go to Step 8 | Go to Step 4 | |||||||||
Did you isolate an exhaust leak? | -- | Go to Step 14 | Go to Step 5 | |||||||||
Inspect the following items:
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 6 | |||||||||
Does the scan tool indicate a voltage within the specified range? | 350-550 mV | Go to Step 7 | Go to Step 10 | |||||||||
Does the scan tool indicate a voltage below the specified value? | 200 mV | Go to Step 13 | Go to Step 9 | |||||||||
|
Important: Determine and correct the cause of the contamination before replacing
a sensor. Inspect for the following conditions:
Replace the affected heated oxygen sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the action? | -- | Go to Step 14 | -- | |||||||||
9 |
Does the DMM indicate a voltage near the specified value? | 5 V | Go to Step 12 | Go to Step 11 | ||||||||
10 | Repair the high signal circuit for a short to ground or short to a voltage. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you complete the action? | -- | Go to Step 14 | -- | ||||||||
11 | Repair the open HO2S low signal circuit, or repair the poor PCM connections. Refer to Heated Oxygen Sensor Wiring Repairs or to Connector Repairs in Wiring Systems. Did you complete the action? | -- | Go to Step 14 | -- | ||||||||
12 | Repair the HO2S high signal circuit for an open, or repair the poor PCM connections. Refer to Heated Oxygen Sensor Wiring Repairs or to Connector Repairs in Wiring Systems. Did you complete the action? | -- | Go to Step 14 | -- | ||||||||
13 | Replace the 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? | -- | Go to Step 14 | -- | ||||||||
14 |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 | ||||||||
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||
