Without Oshawa Assembly

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a bias voltage approximately 450 mV on the Heated Oxygen Sensor (HO2S) signal high and low circuits. When the ignition is turned to the ON position, battery voltage is supplied to the HO2S heater. As the heater reaches operating temperature, the HO2S voltage responds by changing from a bias voltage range to normal operation. Typically, as the HO2S reaches operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, it is possible for the HO2S voltage to go above 450 mV.

The PCM will run the heater test only on a cold start depending on cumulative air flow and only once an ignition cycle. When the engine is started the PCM will monitor the HO2S voltage. When the HO2S voltage goes above or below the bias range threshold, the PCM will determine how much time it took. If the PCM detects that it took too much time for the HO2S to enter into normal operating range, a Diagnostic Trouble Code (DTC) sets. The time it 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
^ No active Mass Air Flow (MAF) DTCs
^ No active Intake Air Temperature (IAT) DTCs
^ No active Engine Coolant Temperature (ECT) DTCs
^ No active Throttle Position (TP) DTCs
^ No active injector DTCs
^ No active crank sensor DTCs
^ No active ignition control DTCs
^ The IAT and 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 voltage is between 10 volts and 18 volts.
^ The secondary Air Injection (AIR), Exhaust Gas Recirculation (EGR), and the catalyst diagnostics are not active.

CONDITIONS FOR SETTING THE DTC
The HO2S voltage remains between 300 mV and 700 mV for a predetermined amount of time depending on ECT and air flow.

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.

DIAGNOSTIC AIDS

IMPORTANT: Remove any debris from the PCM connector surfaces before servicing the PCM. 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 and Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions such as RPM, load, vehicle speed, temperature, etc. that you observed. This will isolate when the DTC failed. For an intermittent condition, refer to Symptoms. Symptom Related Diagnostic Procedures
^ The heater diagnostic only runs on a cold start and only runs 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 Heated Oxygen Sensor (HO2S) Wiring Repairs in Diagrams.
^ For an intermittent condition, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. Allow the engine to cool, before proceeding with this diagnostic table. The HO2S may be at the operating temperature and no drop or rise in the HO2S voltage would occur. If the HO2S voltage stays between 300-700 mV, this indicates the HO2S heater is inoperative.
3. If more than one HO2S heater DTC is set, this is good indication that the HO2S fuse is open. Test all the related circuits going to all of the heated oxygen sensors for a short to ground. If all of the wiring is OK, it may be necessary to disconnect each HO2S one at a time to locate a shorted sensor.
4. This step tests whether an ignition positive voltage supply is available at the sensor.
5. This step tests whether a ground is available at the sensor.
6. This step tests whether the HO2S heater element is internally open.
7. Inspect the ignition positive voltage circuits at the underhood electrical center for poor connections.
8. Test the ground circuits for an open if more than one heater DTC sets.