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

CONDITIONS FOR SETTING THE DTC
^ The HO2S signal voltage remains below 200 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 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.

^ Heated Oxygen Sensor (HO2S) wire The sensor pigtail may be in contact with the exhaust manifold or the exhaust system.
^ An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Diagrams.
^ Check for an intermittent ground in the signal wire between the connector and the sensor. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Lean injectors - 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
^ Fuel contamination - Water near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set a DTC. Refer to Alcohol/Contaminants-in-Fuel Diagnosis. Testing and Inspection
^ Fuel pressure - System will be lean if the fuel pressure is low. Refer to Fuel System Diagnosis Component Tests and General Diagnostics
^ Exhaust leaks - An exhaust leak near the HO2S can cause a lean condition. Refer to Exhaust System Inspection in Engine Exhaust. Testing and Inspection
^ Vacuum or crankcase leaks can cause a lean condition.
^ If the above are OK, the HO2S may be at fault. 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. If the HO2S voltage is fixed well below 200 mV, this indicates a short to battery ground or chassis ground. If the voltage is fixed near or above 200 mV, this indicates a short to a PCM ground.
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 be used to 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 the PCM recorded. This will isolate when the DTC failed.
4. Disconnecting the HO2S and grounding the low reference circuit should cause the HO2S voltage to display a bias voltage. If the voltage is low, inspect the high reference signal circuit for a short to ground.
5. Disconnecting the PCM allows using the DMM in order to test continuity of the circuits. This aids in locating an open or shorted circuit.