The engine control module (ECM) supplies a voltage of about 0.45V between the ECM connector J2 terminals 22 and 3. The oxygen (O2) sensor varies the voltage within a range of about 1V if the exhaust is rich, down to about 0.1V if the exhaust is lean. The O2 sensor is like an open circuit and produces no voltage when it is below 300°C(600°F). An open O2 sensor circuit or a cold O2 sensor causes "open loop" operation.

Normal scan tool voltage varies between 0.1volts and 1.0 volts while in closed loop.

Inspect the oxygen (O2) sensor wire. The O2 sensor may be positioned incorrectly and contacting the exhaust manifold.

Check for an intermittent ground in the wire between the O2 sensor and the engine control module.

Perform an injector balance test to determine if a restricted fuel injector may be causing the lean condition.

Vacuum of crankcase leaks will cause a lean running condition.

An exhaust manifold gasket leak of a cracked exhaust manifold may cause outside air to be pulled into the exhaust and past the sensor.

The engine control module (ECM) supplies a voltage of about 0.45V between the ECM connector J2 terminals 22 and 3. The oxygen (O2) sensor varies the voltage within a range of about 1V if the exhaust is rich, down to about 0.1V if the exhaust is lean. The O2 sensor is like an open circuit and produces no voltage when it is below 300°C(600°F). An open O2 sensor circuit or a cold O2 sensor causes "open loop" operation.

Normal scan tool voltage varies between 0.1volts and 1.0 volts while in closed loop.

Inspect the oxygen (O2) sensor wire. The O2 sensor may be positioned incorrectly and contacting the exhaust manifold.

Check for an intermittent ground in the wire between the O2 sensor and the engine control module.

Perform an injector balance test to determine if a restricted fuel injector may be causing the lean condition.

Vacuum of crankcase leaks will cause a lean running condition.

An exhaust manifold gasket leak of a cracked exhaust manifold may cause outside air to be pulled into the exhaust and past the sensor.

The engine control module (ECM) supplies a voltage of about 0.45V between the ECM connector J2 terminals 22 and 3. The oxygen (O2) sensor varies the voltage within a range of about 1V if the exhaust is rich, down to about 0.1V if the exhaust is lean. The O2 sensor is like an open circuit and produces no voltage when it is below 300°C(600°F). An open O2 sensor circuit or a cold O2 sensor causes "open loop" operation.

Normal scan tool voltage varies between 0.15 to 8.5mV while in Closed Loop. If DTC P0133 is intermittent, refer to "Intermittents" in this section.

Heated oxygen sensors are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the engine control module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air fuel ratio. The ECM supplies the HO2S with a reference voltage of about 0.45V. The HO2S generates a voltage within a range of 0~1V that fluctuates above and below bias voltage once in closed loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and then provide an accurate voltage signal.

The numbers below refer to the step numbers on the diagnostic table.

The engine control module (ECM) supplies a voltage of about 0.45V between the ECM connector J2 terminals 21 and 3. The oxygen (O2) sensor varies the voltage within a range of about 1V if the exhaust is rich, down to about 0.1V if the exhaust is lean. The O2 sensor is like an open circuit and produces no voltage when it is below 300°C(600°F). An open O2 sensor circuit or a cold O2 sensor causes "open loop" operation.

The engine control module (ECM) supplies a voltage of about 0.45V between the ECM connector J2 terminals 21 and 3. The Heated oxygen (O2) sensor varies the voltage within a range of about 1V if the exhaust is rich, down to about 0.1V if the exhaust is lean. The Heated O2 sensor is like an open circuit and produces no voltage when it is below 300°C(600°F). An open O2 sensor circuit or a cold O2 sensor causes "open loop" operation.

Heated oxygen sensors are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the engine control module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air fuel ratio. The ECM supplies the HO2S with a reference voltage of about 0.45V. The HO2S generates a voltage within a range of 0~1V that fluctuates above and below bias voltage once in closed loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and then provide an accurate voltage signal.

The Engine Control Module (ECM) has four individual injector driver circuits, each of which controls an injector. When a driver circuit is grounded by the ECM, the injector is activated. The ECM monitors the current in each driver circuit. The ECM measures a voltage drop through a fixed resistor and controls it. The voltage on each driver is monitored to detect a fault. If the voltage is not what the ECM expects to monitor on the circuit, a Diagnostic Trouble Code (DTC) is set. This DTC detects a short to ground and/or an open circuit and short to battery conditions for low-side drive injector outputs.

An injector 1 driver circuit that is open or shorted to voltage will cause a DTC P0201 to set. It will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which injector is inoperative.

Long-term and short-term fuel trims that are excessively high or low are a good indication that an injector is malfunctioning. Refer to "Fuel Injector Balance Test" in this section to check for malfunctioning injectors.

The injector resistance tested at the ECM connection is slightly more than if tested directly at the injector because it includes resistance of the harness wires. The normal value is about 13.5 Ω

The Engine Control Module (ECM) has four individual injector driver circuits, each of which controls an injector. When a driver circuit is grounded by the ECM, the injector is activated. The ECM monitors the current in each driver circuit. The ECM measures a voltage drop through a fixed resistor and controls it. The voltage on each driver is monitored to detect a fault. If the voltage is not what the ECM expects to monitor on the circuit, a Diagnostic Trouble Code (DTC) is set. This DTC detects a short to ground and/or an open circuit and short to battery conditions for low-side drive injector outputs.

An injector 2 driver circuit that is open or shorted to voltage will cause a DTC P0202 to set. It will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which injector is inoperative.

Long-term and short-term fuel trims that are excessively high or low are a good indication that an injector is malfunctioning. Refer to "Fuel injector Balance Test" in this section to check for malfunctioning injectors.

The injector resistance tested at the ECM connection is slightly more than if tested directly at the injector because it includes resistance of the harness wires. The normal value is about 13.5 Ω

The Engine Control Module (ECM) has four individual injector driver circuits, each of which controls an injector. When a driver circuit is grounded by the ECM, the injector is activated. The ECM monitors the current in each driver circuit. The ECM measures a voltage drop through a fixed resistor and controls it. The voltage on each driver is monitored to detect a fault. If the voltage is not what the ECM expects to monitor on the circuit, a Diagnostic Trouble Code (DTC) is set. This DTC detects a short to ground and/or an open circuit and short to battery conditions for low-side drive injector outputs.

An injector 3 driver circuit that is open or shorted to voltage will cause a DTC P0203 to set. It will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which injector is inoperative.

Long-term and short-term fuel trims that are excessively high or low are a good indication that an injector is malfunctioning. Refer to "Fuel Injector Balance Test" in this section to check for malfunctioning injectors.

The injector resistance tested at the ECM connection is slightly more than if tested directly at the injector because it includes resistance of the harness wires. The normal value is about 13.5 Ω.

The Engine Control Module (ECM) has four individual injector driver circuits, each of which controls an injector. When a driver circuit is grounded by the ECM, the injector is activated. The ECM monitors the current in each driver circuit. The ECM measures a voltage drop through a fixed resistor and controls it. The voltage on each driver is monitored to detect a fault. If the voltage is not what the ECM expects to monitor on the circuit, a Diagnostic Trouble Code (DTC) is set. This DTC detects a short to ground and/or an open circuit and short to battery conditions for low-side drive injector outputs.

An injector 4 driver circuit that is open or shorted to voltage will cause a DTC P0204 to set. It will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which injector is inoperative.

Long-term and short-term fuel trims that are excessively high or low are a good indication that an injector is malfunctioning. Refer to "Fuel injector Balance Test" in this section to check for malfunctioning injectors.

The injector resistance tested at the ECM connection is slightly more than if tested directly at the injector because it includes resistance of the harness wires. The normal value is about 13.5 Ω.