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, and decreases the signal voltage as the engine runs leaner. 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 diagnostic trouble code (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, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0200, P0300, P0440, P0442, P0446, P0452, P0453, 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) sensor is between 18-45 g/s. |
| • | The engine speed is between 1,300-3,000 RPM. |
| • | The throttle position (TP) is more than 5 percent. |
| • | The engine is in Closed Loop status. |
| • | The ignition 1 signal voltage 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 evaporative emissions (EVAP) purge solenoid command is more than 1 percent. |
| • | 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 powertrain control module (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 the 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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After the HO2S heater is commanded 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 reference circuit, and the PCM are OK.
-
The opposite bank HO2S must be disconnected to isolate a short to ground in the HO2S heater high control circuit.
-
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 8 | Go to Step 6 | |||||||||||
6 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 7 | ||||||||||
7 | Test for an open between terminal A of the affected sensor harness connector and the following PCM terminals:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 10 | |||||||||||
9 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 13 | ||||||||||
10 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||
11 |
Important: Perform the following test on HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1. A condition in either sensor will cause this DTC to set. Test the HO2S heater high control 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 18 | Go to Step 12 | ||||||||||
|
Important: Perform the following test on HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1. A condition in either sensor will cause this DTC to set. Measure the resistance between the HO2S heater high control circuit, sensor side, and the HO2S heater low reference circuit, sensor side. Refer to Circuit Testing in Wiring Systems. Does the resistance of either sensor measure above or below the specified range? | 2-50 ohms | Go to Step 18 | Go to Step 15 | |||||||||||
13 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||||||
14 | 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 19 | Go to Step 17 | ||||||||||
15 |
Important: Before replacing the suspected HO2S, check and remove any source of contamination. Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||||||||
16 | 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 | Go to Step 18 | ||||||||||
17 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||||||||
18 | Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||||||||
19 |
Does the DTC run and pass? | -- | Go to Step 20 | Go to Step 2 | ||||||||||
20 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||||
