Circuit Description
The powertrain control module (PCM) supplies a bias voltage of approximately 450 mV on the heated oxygen sensor (HO2S) high and low signal circuits. When you turn ON the ignition, battery voltage is supplied to the HO2S heater. As the heater reaches the operating temperature, the HO2S voltage responds by changing from a bias voltage range to the normal operation. Typically, as the HO2S reaches the operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, the HO2S voltage can go above 450 mV.
Depending on the cumulative air flow, the PCM runs the heater test only during a cold start, and only once an ignition cycle. When you start the engine, the PCM monitors the HO2S voltage. When the HO2S voltage goes above or below the bias range threshold, the PCM determines how much time the process took. If the PCM detects that the process took too much time for the HO2S to enter into normal operating range, a DTC sets. This time is based on the amount of air that flows into the engine.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0134, P0137, P0138, P0140, P0151, P0152, P0154, P0157, P0158, P0160, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1258, P1415, P1416, or P1441 are not set. |
| • | The intake air temperature (IAT) and the engine coolant temperature (ECT) are less than 50°C (122°F) and are within 8°C (14.5°F) of each other at engine start-up. |
| • | The ignition 1 signal is between 9-18 volts. |
| • | The HO2S voltage is between 425-475 mV at engine start-up. |
| • | The scan tool output controls are not active. |
| • | The intrusive tests are not in progress. |
| • | The mass air flow (MAF) is less than 18 g/s. |
Conditions for Setting the DTC
The HO2S voltage remains within 150 mV of the start-up voltage for a predetermined amount of time, based on the engine coolant temperature and the air flow.
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
| • | This diagnostic may fail due to a restriction in the secondary air injection (AIR) system. Refer to DTC P1415 or P1416 . |
| • | For an intermittent condition refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Before you perform this test, allow the engine to cool If the sensor is at the operating temperature, the HO2S voltage will stay high or low. If the HO2S voltage stays between 300-700 mV, the HO2S heater is inoperative.
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If more than one HO2S DTC is set, the HO2S fuse may be open. Test all the related circuits going to all the heated oxygen sensors for a short to ground. If all the wiring is OK, you may need to disconnect each HO2S one at a time in order to locate a shorted sensor.
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This step verifies whether an ignition voltage is available at the sensor.
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This step verifies whether ground is available at the sensor.
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This step verifies whether the HO2S heater element is internally open.
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Inspect the ignition 1 voltage circuits at the underhood electrical center for poor connections.
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If more than one heater DTC sets, test the ground circuits for an open.
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:
Does the HO2S voltage go from a bias voltage to above or below the specified range? | 300-600 mV | Go to Diagnostic Aids | Go to Step 3 | |||||
Inspect the HO2S fuse for an open. Is the HO2S fuse open? | -- | Go to Step 11 | Go to Step 4 | |||||
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 7 | |||||
Connect the test lamp between the HO2S ignition 1 voltage and the HO2S heater ground. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 8 | |||||
Measure the resistance between the HO2S ignition 1 voltage and the HO2S heater ground at the HO2S pigtail using a DMM. Is the HO2S resistance within the specified range? | 2-50 ohms | Go to Step 9 | Go to Step 10 | |||||
Repair the open in the HO2S ignition 1 voltage circuit to the HO2S. Refer to Wiring Repairs in Wiring Systems . Did you complete the repair? | -- | Go to Step 12 | -- | |||||
Repair the open in the HO2S heater ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 12 | -- | |||||
9 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||
10 | Replace the affected HO2S. Refer to: Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
11 |
Did you complete the repair? | -- | Go to Step 12 | -- | ||||
12 |
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 | ||||
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
