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 the ignition ON, the 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.
The PCM runs the heater test only on a cold start, depending on the cumulative air flow, and only once an ignition cycle. When you start the engine, the PCM monitors the HO2S voltage. If the HO2S voltage goes above or below the bias range threshold, the PCM determines how much time passed. If the PCM detects that the process took too much time for the HO2S to enter into normal operating range, a DTC sets. The time the process takes the HO2S to reach the operating temperature 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, P0117, P0118, P0131, P0132, P0134, P0137, P0138, P0140, P0151, P0152, P0154, P0157, P0158, P0160, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1221, P1258, P1415, P1416, P1441, P1514, P1515, P1516, P1517, or P1518 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 secondary air injection (AIR) and the catalyst diagnostics are not active. |
| • | The scan tool is disconnected. |
| • | The mass air flow (MAF) is less than 18 g/s. |
Conditions for Setting the DTC
The HO2S voltage remains between 300-600 mV for a predetermined amount of time, depending 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
Important:
• Before you service the PCM and throttle actuator control (TAC) module, remove any debris from the module connector surfaces. Inspect the module connector gaskets when you diagnose or replace the modules. Ensure that the gaskets are correctly installed.
The gaskets prevent contaminate intrusion into the modules. • For any test that requires probing the PCM or probing a component harness connector, use the connector test adapter kit
J 35616
. Using this kit prevents damage to the harness and component terminals.
Refer to
Using Connector Test Adapters
in Wiring Systems.
| • | The heater diagnostic will only run on a cold start and will run once per ignition cycle. |
| • | An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Wiring Repairs in Wiring Systems. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
| • | This diagnostic may fail due to a restriction in the secondary air injection (AIR) system. Refer to DTC P1415 or P1416 . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Allow the engine to cool before you perform this test. 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.
-
If more than one HO2S DTC is set, this is a good indication that the HO2S fuse is open. Test all the related circuits that go 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.
-
This verifies whether B+ supply is available at the sensor.
-
This step verifies whether a ground is available at the sensor.
-
This step determines whether the HO2S heater element is internally open.
-
Inspect the ignition feed circuits at the underhood electrical center for proper connections.
-
Inspect the splice pack for the ground circuits for an open circuit. A condition at the splice pack sets more than one heater DTC.
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 1/2 hour before proceeding with this table. Important: If DTC P0300 is set, diagnose that DTC first. Refer to Diagnostic Trouble Code (DTC) List .
Does the HO2S voltage go from a bias voltage to above or below the specified range? | 300-700 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 3 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 3 voltage and the HO2S heater ground at the HO2S sensor side with the DMM. Is the HO2S resistance within the specified range? | 3.5-14 ohms | Go to Step 9 | Go to Step 10 | |
Repair the open in the HO2S ignition 3 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 that has been diagnosed. 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 | |
