Circuit Description
Heated oxygen sensors (HO2S) are used to minimize the amount of time required to enter Closed Loop fuel control operation and to allow accurate catalyst monitoring. The HO2S heater is fed power directly from ignition 1. The HO2S heater control circuit or heater ground is connected to the powertrain control module (PCM). The PCM controls HO2S heater operation by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. The driver for the HO2S heater control circuit has the ability to measure the amount of current drawn by the controlled device.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0440, P0446, P0452, P0453, P0507, P0601, P0602, P0604, P0606, P1120, P1220, P1221, P1271, P1275, P1280, P1484, P1512, P1514, P1515, P1516, P1621, P1635, P1639, P1680, or P1681 are not set. |
| • | The ignition 1 signal is between 10-16.5 volts. |
| • | The engine coolant temperature (ECT) is more than 70°C (158°F). |
| • | The air flow calculated is less than 60 g/s. |
| • | The fuel level sensor is more than 10 percent. |
| • | The engine run time is more than 60 seconds. |
Conditions for Setting the DTC
The HO2S heater current is not within the calibrated range for more than 200 seconds.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Allow the engine to cool before performing this test. This allows the HO2S to cool which causes the HO2S signal voltage to return to near bias voltage, approximately 450 mV. This test determines if ground is constantly being applied to the HO2S heater.
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After the HO2S heater is commanded ON, the HO2S will heat up. This will cause the signal voltage to change either more than or less than bias voltage, verifying the HO2S heater is operating.
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This step tests for voltage at the HO2S heater. The O2 fuse supplies power to the HO2S heater.
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This step verifies that the PCM is providing ground to the HO2S heater.
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This step tests if ground is constantly being applied to the HO2S heater.
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If more than one HO2S DTC is set, this is a good indication that the O2 fuse is open. Test all related circuits going to all the heated oxygen sensors for a short to ground. If you cannot locate a shorted circuit, it may be necessary to disconnect each HO2S one at a time to locate a shorted sensor.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
|
Important: Allow the engine to cool for about one half hour before proceeding with this diagnosis.
Does the HO2S signal voltage go from bias voltage to more than or less than the specified range? | 300-600 mV | Go to Step 8 | Go to Step 3 | |
Does the HO2S signal voltage go from bias voltage to more than or less than the specified range? | 300-600 mV | Go to Intermittent Conditions | Go to Step 4 | |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 11 | |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 9 | Go to Step 6 | |
Does the test lamp remain illuminated with each command? | -- | Go to Step 8 | Go to Step 7 | |
7 | Test the HO2S heater low control circuit for a short to voltage or an open. 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 14 | Go to Step 10 |
8 | Test the HO2S heater low control circuit for a short to ground. 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 14 | Go to Step 10 |
9 | Inspect for poor connections at the HO2S connector. 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 14 | Go to Step 12 |
10 | 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 14 | Go to Step 13 |
Repair the HO2S ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- | |
12 | Replace the appropriate HO2S. Refer to the following procedures: Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | 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 | |
