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 a 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 rich, the signal voltage is high. 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 fuel 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 determines if the difference in transition times from lean-to-rich or rich-to-lean has exceeded a maximum ratio. The powertrain control module (PCM) monitors the time needed for the HO2S to transition from more than 600 mV to less than 300 mV and vice versa. If either of these times is longer than the other by a calibrated ratio, this DTC is set.
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) is more than 57°C (135°F). |
| • | The engine run time is more than 160 seconds. |
| • | The mass air flow (MAF) 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 HO2S transition time ratio is not within a calibrated range.
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: Before you service the PCM, remove any debris from the PCM connector surfaces. 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.
| • | Using the Freeze Frame/Failure Records may help to locate an intermittent condition. If you cannot duplicate the DTC, use the information in the Freeze Frame/Failure Records in order to determine how many miles have occurred since the DTC set. You can also use the Fail Counter and the Pass Counter in order to determine how many ignition cycles have occurred in which the diagnostic reported a pass or a fail. In order to isolate when the DTC failed, operate vehicle within the same Freeze Frame conditions that you observed. These conditions include: |
| - | The RPM |
| - | The vehicle load |
| - | The vehicle speed |
| - | The temperature |
| • | An oxygen supply inside the HO2S is necessary for proper operation. This oxygen supply is provided through the HO2S wires. Inspect all HO2S wires and connections for breaks or for contamination. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. |
For an intermittent, refer to Symptoms - Engine Controls .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the fault is present. This test may take 5 minutes for the diagnostic to run. For any test that requires probing the PCM or probing a component harness connector, use the Connector Test Adapter Kit . Using this kit prevents damage to the harness connector terminals.
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When DTC P1134 and DTC P1154 are set at the same time, fuel contamination condition is likely.
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An exhaust leak 152.4-304.8 mm (6-12 inches) from the HO2S can cause a DTC to set.
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This step tests the HO2S for being tight and determines if the connectors and the circuits are OK.
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This step tests the integrity of the HO2S low signal circuit to the PCM.
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This step tests the integrity of the high signal circuits to the PCM.
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Certain room temperature vulcanizing (RTV) silicon gasket materials release vapors that can contaminate the HO2S. Silicon in the fuel can also cause silicon contamination. If the sensors appear to be silicon-contaminated, and if all the silicon sealant is a non-silicon base, advise the customer to try a different fuel company. A missing fuel filler restrictor may indicate that the customer has 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 P1134 or P1154, refer to those DTCs before proceeding with this diagnostic table.
Did DTC P1134 or P1154 fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | |||||||||
Did both DTC P1134 and P1154 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 conditions:
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 6 | |||||||||
Does the scan tool indicate a voltage that is within the specified range? | 350-550 mV | Go to Step 7 | Go to Step 10 | |||||||||
Does the scan tool indicate a voltage that is less than the specified value? | 200 mV | Go to Step 13 | Go to Step 9 | |||||||||
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Important: Before you replace a sensor, determine and correct the cause of the
contamination. Inspect for the following conditions:
Replace the affected Heated Oxygen Sensor (H20S). 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 | -- | |||||||||
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 for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the action? | -- | Go to Step 14 | -- | ||||||||
11 | Repair the open HO2S low circuit, or repair the poor PCM connections. Refer to Wiring 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 Wiring Repairs in Wiring Systems. Did you complete the action? | -- | Go to Step 14 | -- | ||||||||
13 | 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? | -- | 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 | |||||||||
