DTCs should be cleared after repairs have been completed. Some diagnostic tables will tell you to clear the codes before using the chart. This allows the ECM to set the DTC while going through the chart, which will help to find the cause of the problem more quickly.

The DTC P0031 monitors the HO2S heater circuit current. The heater is powered through the ignition switch and is grounded through the ECM heater control. The ECM commands the heater ON by grounding the heater control circuit. The HO2S sensor must be at operating temperature in order to accurately measure the oxygen content of the exhaust gas. The heater allows the HO2S to reach operating temperature quickly.

An intermittent malfunction may be caused by a problem in the HO2S electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to "Intermittent".

If a DTC P0031 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The DTC P0032 monitors the HO2S heater circuit current. The heater is powered through the ignition switch and is grounded through the ECM heater control. The ECM commands the heater ON by grounding the heater control circuit. The HO2S sensor must be at operating temperature in order to accurately measure the oxygen content of the exhaust gas. The heater allows the HO2S to reach operating temperature quickly.

An intermittent malfunction may be caused by a problem in the HO2S electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to "Intermittent".

If a DTC P0032 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The DTC P0037 monitors the HO2S heater circuit current. The heater is powered through the ignition switch and is grounded through the ECM heater control. The ECM commands the heater ON by grounding the heater control circuit. The HO2S sensor must be at operating temperature in order to accurately measure the oxygen content of the exhaust gas. The heater allows the HO2S to reach operating temperature quickly.

An intermittent malfunction may be caused by a problem in the HO2S electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to "Intermittent".

If a DTC P0037 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The DTC P0038 monitors the HO2S heater circuit current. The heater is powered through the ignition switch and is grounded through the ECM heater control. The ECM commands the heater ON by grounding the heater control circuit. The HO2S sensor must be at operating temperature in order to accurately measure the oxygen content of the exhaust gas. The heater allows the HO2S to reach operating temperature quickly.

An intermittent malfunction may be caused by a problem in the HO2S electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to "Intermittent".

If a DTC P0038 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the low control circuit by a low side driver within the control module. The control module monitors the current draw of the heater to determine if a failure is present.

The engine control module (ECM) uses the Manifold Absolute Pressure (MAP) sensor to control the fuel delivery and the ignition timing. The MAP sensor measures the changes in the intake manifold pressure, which results from engine load (intake manifold vacuum) and the rpm changes; and converts these into voltage outputs. The ECM sends a 5 volt-reference voltage to the MAP sensor. As the manifold pressure changes, the output voltage of the MAP sensor also changes. By monitoring the MAP sensor output voltage, the ECM knows the manifold pressure. A low-pressure (low voltage) output voltage will be about 1.0 to 1.5 volts at idle, while higher pressure (high voltage) output voltage will be about 4.5 to 4.8 at wide open throttle (WOT). The MAP sensor is metric pressure, allowing the ECM to make adjustments for different altitudes.

(P0107)

(P0108)

(P0107)

(P0108)

With the ignition ON and the engine stopped, the manifold pressure is equal to atmosphere pressure and the signal voltage will be high.

The ECM as an indication of vehicle altitude uses this information. Comparison of this reading with a known good vehicle with the same sensor is a good way to check the accuracy of a suspect sensor. Readings should be the same ± 0.4volt.

If this DTC is intermittent, refer to "Manifold Absolute Pressure Check" in this section for further diagnosis.

If the connections are OK, monitor the manifold absolute pressure (MAP) sensor signal voltage while moving related connectors and the wiring harness. If the failure is induced, the display on the scan tool will change. This may help to isolate the location of an intermittent malfunction.

The Intake Air Temperature (IAT) Sensor uses a thermistor to control the signal voltage to the engine control module (ECM). The ECM supplies a 5 volt reference voltage and a ground to the sensor. When the air is cold, the resistance is high ; therefore IAT sensor signal voltage will be high. If the intake air is warm, resistance is low ; therefore the IAT sensor signal voltage will be low.

The Intake Air Temperature (IAT) Sensor uses a thermistor to control the signal voltage to the engine control module (ECM). The ECM supplies a 5 volt reference voltage and a ground to the sensor . when the air is cold, the resistance is high ; therefore IAT sensor signal voltage will be high. If the intake air is warm, resistance is low ; therefore the IAT sensor signal voltage will be low.

The Engine Coolant Temperature (ECT) sensor uses a thermistor to control the signal voltage to the engine control module (ECM).

The ECM supplies a voltage on the signal circuit to the sensor. When the engine coolant is cold, the resistance is high; therefore the ECT signal voltage will be high.

As the engine warms, the sensor resistance becomes low, and the voltage drops. At normal engine operating temperature, the voltage will be between 1.5 and 2.0 volts at the ECT signal terminal.

The ECT sensor is used to the following items:

After the engine has started, the ECT should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens.

Use the temperature vs. Resistance values table to evaluate the possibility of a skewed sensor. Refer to "Temperature vs. Resistance" in this section.

The Engine Coolant Temperature (ECT) uses a thermistor to control the signal voltage to the engine control module (ECM).

The ECM supplies a voltage on the signal circuit to the sensor. When the engine coolant is cold, the resistance is high; therefore the ECT sensor signal voltage will be high.

As the engine warms, the sensor resistance becomes low, and the voltage drops. At normal engine operating temperature, the voltage will be between 1.5 and 2.0 volts at the ECT signal terminal.

The ECT sensor is used to the following items:

After the engine has started, the ECT should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens.

Use the temperature vs. Resistance values table to evaluate the possibility of a skewed sensor. Refer to "Temperature vs. Resistance" in this section.

The Engine Control Module (ECM) supplies a 5 volt reference voltage signal and a ground to the Throttle Position (TP) sensor. The TP sensor sends a voltage signal back to the ECM relative to the throttle plate opening. The voltage signal will vary from approximately 0.33 volts at closed throttle, to over 4.3 volts at Wide Open Throttle (WOT).

The TP signal is used by the ECM for fuel control and for most of the ECM controlled outputs. The TP signal is one of the most important inputs used by the ECM for fuel control and most of the ECM controlled outputs.

If the DTC P0122 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use a scan tool information data to determine the status of the DTC. If the dc occurs intermittently, using the Diagnostic table may help isolate the problem.

Number(s) below refer to the step number(s) on the Diagnostic Table.

The Engine Control Module (ECM) supplies a 5 volt reference voltage signal and a ground to the Throttle Position (TP) sensor. The TP sensor sends a voltage signal back to the ECM relative to the throttle plate opening. The voltage signal will vary from approximately 0.33 volts at closed throttle, to over 4.3 volts at Wide Open Throttle (WOT).

The TP signal is used by the ECM for fuel control and for most of the ECM controlled outputs. The TP signal is one of the most important inputs used by the ECM for fuel control and most of the ECM controlled outputs.

If the DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use a scan tool information data to determine the status of the DTC. If the dc occurs intermittently, using the Diagnostic table may help isolate the problem.

With ignition ON and the throttle at closed position, the voltage should read between 0.2 and 0.90 volts and increase steadily to over 4.3 volts at WOT.

DTCs P0123 and P0113 stored at the same time could be result of an open sensor ground circuit.

Number(s) below refer to the step number(s) on the Diagnostic Table.