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 voltage of about 450 mV between the Heated Oxygen Sensor (HO2S) high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The PCM monitors the HO2S voltage for being fixed above a predetermined voltage. If the PCM detects the voltage is above a predetermined voltage, a Diagnostic Trouble Code (DTC) sets.

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 secondary Air Injection (AIR), Exhaust Gas Recirculation (EGR), and the Catalyst diagnostics are not active.
^ The ignition voltage is more than 9 volts.
^ The fuel system is operating in Closed Loop.
^ The fuel trim learn is enabled.
^ The TP angle is between 2 percent and 70 percent.

CONDITIONS FOR SETTING THE DTC
^ The HO2S signal voltage remains above 775 mV.
^ The conditions are present for 33 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip 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 drive trip, 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.
^ Open Loop fueling for the entire ignition cycle.

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.

^ Check the HO2S electrical connections for evidence of water intrusion. Water present in the connector causes the B+ supply to the heater to bleed over to the signal circuit.
^ Fuel pressure - The system goes rich if the pressure is too high. The PCM compensates for some increase. However, if the fuel pressure is too high, a DTC may set. Refer to Fuel System Diagnosis. Component Tests and General Diagnostics
^ Rich injector - Perform the Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool. Component Tests and General Diagnostics Component Tests and General Diagnostics
^ Leaking injector- Refer to Fuel System Diagnosis. Component Tests and General Diagnostics
^ Fuel pressure regulator - Inspect the vacuum line going to the fuel pressure regulator for evidence of fuel. Refer to the Fuel System Diagnosis. Component Tests and General Diagnostics
^ Evaporative Emissions (EVAP) canister purge - Inspect the canister for fuel saturation. If full of fuel, check the canister control and hoses. Refer to Evaporative Emission (EVAP) Control System Operation Description.
^ MAF sensor - Disconnect the MAF sensor and see if the rich condition is corrected. If so, check for proper installation. If installed OK, replace the MAF sensor. If the MAF sensor is installed backwards, the system goes rich. The plastic portion of the sensor has arrows cast into it indicating proper air flow direction. The arrows must point towards the engine.
^ 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.
^ TP sensor - An intermittent TP sensor output causes the system to go rich, due to a false indication of the engine accelerating. 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. This step tests for a rich condition.
The engine must be at the normal operating temperature before performing this test.
3. 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 aid in determining 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 the PCM recorded. This will isolate when the DTC failed.
4. If the voltage remains high, this indicates the signal circuit is shorted to a voltage. If the voltage goes low, this indicates a rich condition.
5. This step isolates the condition. If the voltage remains high, this indicates the signal circuit is not shorted to the heater positive voltage circuit.
8. Review the system mechanization. Test for a short between the HO2S signal circuit and any other wires powered by this fuse that run together inside the same harness.