Engine Control System - 3.8l - DTC p0016 to DTC p0206 Buick LaCrosse I

Circuit Description

The powertrain control module (PCM) uses the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor signals to monitor the correlation between the crankshaft and camshaft positions. If the PCM detects that the timing between the crankshaft and the camshaft is incorrect, DTC P0016 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P0016 Crankshaft Position (CKP) - Camshaft Position (CMP) Correlation

Conditions for Running the DTC

1. DTCs P0335, P0336, P0340, P0341, P0385, P0386 are not set.
2. The diagnostic runs continuously when the above condition is met.

Conditions for Setting the DTC

The PCM detects that the timing between the crankshaft and the camshaft is incorrect for less than 1 second.

Action Taken When the DTC Sets

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Inspect the engine for any recent engine mechanical repairs. An incorrectly installed camshaft, crankshaft or timing chain can cause this DTC to set.

Test Description

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

1. 2: This step determines if a condition is present.
2. 5: This step inspects for any recent engine mechanical repairs. An incorrectly installed camshaft, crankshaft or timing chain can cause this DTC to set.

DTC P0016

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms, once per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms, once per second.

If the PCM detects there is a circuit fault present on the HO2S 1 heater low control circuit, DTC P0030 for bank 1 sensor 1 will set.

The HO2S 1 has the following circuits

1. A HO2S 1 high signal circuit
2. A HO2S 1 low reference circuit
3. A HO2S 1 heater ignition voltage circuit
4. A HO2S 1 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0030 HO2S Heater Control Circuit Bank 1 Sensor 1

The following conditions must be met

1. The engine is cranking or running.
2. The system voltage is between 11-18 volts.

1. The PCM detects that the HO2S 1 heater control circuit status is incorrect for more than 2 seconds.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0030

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms, once per second. when the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms, once per second.

If the PCM detects there is a circuit fault present on the HO2S 1 heater low control circuit, DTC P0036 for bank 1 sensor 2 will set.

The HO2S 2 has the following circuits

1. A HO2S 2 high signal circuit
2. A HO2S 2 low reference circuit
3. A HO2S 2 heater ignition voltage circuit
4. A HO2S 2 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0036 HO2S Heater Control Circuit Bank 1 Sensor 2

The following conditions must be met

1. The engine is cranking or running.
2. The system voltage is between 11-18 volts.

1. The PCM detects that the HO2S 2 heater control circuit status is incorrect for more than 2 seconds.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0036

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 of the exhaust stream. When the vehicle is first started, the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. 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 to provide an accurate voltage signal. The PCM controls the HO2S 1 heater low control circuit with a low side driver. The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms once per second. If the PCM detects that the HO2S 1 heater low control circuit current level is not within the calibrated range, DTC P0053 will set for bank 1 sensor 1.

The HO2S 1 has the following circuits

1. The HO2S 1 high signal circuit
2. The HO2S 1 low reference circuit
3. The HO2S 1 ignition 1 voltage circuit
4. The HO2S 1 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0053 HO2S Heater Resistance Bank 1 Sensor 1

1. The ignition is OFF for more than 10 hours.
2. The ECT Sensor parameter minus the IAT Sensor parameter is less than 8°C (14°F) at engine start-up.
3. The ECT Sensor parameter is between -30 and +45°C (-22 and +133°F) at engine start-up.
4. The system voltage is between 9-18 volts.
5. This diagnostic runs one time per valid cold start once the above conditions are met.

The PCM detects that the HO2S 1 heater calculated resistance is not within an expected range at engine start-up for 1 second.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

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

1. 5: This step determines if high resistance is present in the HO2S 1 ignition 1 voltage circuit.
2. 6: This step determines if high resistance is present in the HO2S 1 heater low control circuit.

DTC P0053

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 of the exhaust stream. When the vehicle is first started, the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. 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 to provide an accurate voltage signal. The PCM controls the HO2S 2 heater low control circuit with a low side driver. The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms once per second. If the PCM detects that the HO2S 2 heater low control circuit current level is not within the calibrated range, DTC P0054 will set for bank 1 sensor 2.

The HO2S 2 has the following circuits

1. The HO2S 2 high signal circuit
2. The HO2S 2 low reference circuit
3. The HO2S 2 ignition 1 voltage circuit
4. The HO2S 2 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0054 HO2S Heater Resistance Bank 1 Sensor 2

1. The ignition is OFF for more than 10 hours.
2. The ECT Sensor parameter minus the IAT Sensor parameter is less than 8°C (14°F) at engine start-up.
3. The ECT Sensor parameter is between -30 and +45°C (-22 and +133°F) at engine start-up.
4. The system voltage is between 9-18 volts.
5. This diagnostic runs once per valid cold start once the above conditions are met.

The PCM detects that the HO2S 2 heater calculated resistance is not within an expected range at engine start-up for 1 second.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0054

The actual throttle position (TP) is compared to an expected throttle position based on engine load. The powertrain control module (PCM) determines engine load based on inputs from the mass air flow (MAF) sensor and the manifold absolute pressure (MAP) sensor. Further comparisons are done to distinguish if a sensor is at fault and the respective DTC will set. If the PCM detects that the current load and throttle position are not consistent with the expected load and throttle position, DTC P0068 will set.

This diagnostic procedure supports the following DTC

DTC P0068 Throttle Body Airflow Performance

1. DTCs P0101, P0102, P0103, P0107, P0108, P0120, P0220, P0606, P1106, P1107, P1516, P1518, P2101, P2107, P2108, P2119 and U0107 are not set.
2. The engine speed is more than 600 RPM.

The PCM detects that the throttle position and indicated engine load do not correspond with the expected load and throttle position.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0068

Diagnostic Fault Information

DTC P0101

Circuit/System Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The control module uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has the following circuits

1. An ignition 1 voltage circuit
2. A ground circuit

The control module applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,000 Hertz at idle to near 10,000 Hertz at maximum engine load. The control module uses the following sensor inputs to calculate a predicted MAF value

1. The barometric pressure (BARO) at key ON
2. The manifold absolute pressure (MAP) sensor
3. The intake air temperature (IAT) sensor
4. The engine coolant temperature (ECT) sensor
5. The throttle position indicated angle
6. The engine speed (RPM)

The control module compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine if the signal is stuck based on a lack of variation or is too low or too high for a given operating condition. If the control module detects the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value, DTC P0101 sets.

1. DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125-L32 only, P0128, P0401, P0403, P0404, P0405, P0406, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P1106, P1107, P1111, P1112, P1114, P1115 or P1404 are not set.
2. The engine is running.
3. The ignition 1 signal is between 9-18 volts.
4. If the ignition 1 signal is less than 11.5 volts, then the MAF must be less than 40 g/s.
5. The throttle position indicated angle is less than or equal to 100 percent.
6. The change in the throttle position indicated angle is less than or equal to 15 percent.
7. The traction control is inactive, if equipped.
8. The exhaust gas recirculation (EGR) flow diagnostic is inactive.
9. The EGR is less than or equal to 100 percent.
10. The EGR DC is less than or equal to 100 percent.
11. The EVAP canister purge valve duty cycle is less than or equal to 100 percent.
12. The MAP sensor is less than 80 kPa.
13. The change in the MAP sensor is less than 5 kPa.
14. The above conditions are met for more than 2 seconds.

The control module detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 40 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components: Any aftermarket accessories-Refer to «Checking Aftermarket Accessories»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__checking-aftermarket-accessories) . The secondary ignition wires or coils Any solenoids Any relays Any motors
2. A low minimum air rate through the sensor bore at idle or during deceleration may cause this DTC to set. Inspect for the following conditions: Any deposits on the throttle plate or in the throttle bore Any vacuum leak downstream of the MAF sensor
3. Inspect for any contamination or debris on the sensing elements of the MAF sensor.
4. Inspect the air induction system for any water intrusion. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set.
5. A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 3-10 g/s at idle to 150 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
6. Inspect for a skewed or stuck ECT sensor.
7. A high resistance of 15 ohms or more on the ignition 1 voltage circuit may cause this DTC to set. A high resistance may cause a driveability concern before this DTC sets.
8. The BARO that is used in order to calculate the predicted mass air flow value is initially based on the MAP sensor at key ON. When the engine is running, the BARO value is continually updated near wide open throttle. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. The value shown for the MAP sensor parameter varies with the altitude. With the ignition ON and the engine OFF, 101 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
9. A high resistance on the low reference circuit of the MAP sensor may cause this DTC to set.
10. If the condition is intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

Special Tools Required

J 38522 Variable Speed Generator

Schematic Reference

Engine Controls Schematics

Connector End View Reference

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)
5. «Measuring Voltage Drop»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__measuring-voltage-drop)

Circuit/System Testing

1. Turn ON the ignition, with the engine OFF.
2. Measure the battery voltage.
3. Disconnect the MAF sensor.
4. Connect a test lamp between the MAF sensor ignition 1 voltage circuit and a good ground.
5. With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a good ground. If the voltage is not within 1.5 volts of battery voltage, repair the high resistance in the circuit.
6. Measure the voltage between the MAF sensor signal circuit and a good ground for 4.9-5.2 volts. If the voltage is less than 4.9 volts, test the circuit for a high resistance. If the voltage is within 4.9-5.2 volts, test the circuit for a short to the IAT signal circuit or to any other 5-volt reference circuit.
7. Turn OFF the ignition and all electrical accessories. Allow sufficient time for the control module to power down before taking a resistance measurement.
8. Measure the resistance between the ground circuit of the MAF sensor and a good ground for less than 5 ohms of resistance. You should measure less than 5 ohms of resistance. If the resistance is more than 5 ohms, repair the high resistance in the ground circuit.
9. Connect the J 38522 to the signal circuit of the MAF sensor and a good ground.
10. To set up the variable speed generator, use the switches to set the duty cycle to normal, the frequency to 5 K and the signal switch to 5 volts.
11. Start the engine and observe the MAF Sensor parameter for a range of 4,950-5,025 Hertz. If the MAF Sensor parameter is not within 4,950-5,025 Hertz, replace the control module. If the MAF Sensor parameter is within 4,950-5,025 Hertz, replace the MAF sensor.

Repair Procedures

Throttle Body Assembly Replacement

Repair Verification

Diagnostic Repair Verification

DTC P0102 or P0103

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The control module uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has the following circuits

1. An ignition 1 voltage circuit
2. A ground circuit
3. A signal circuit

The control module applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,000 Hertz at idle to near 10,000 Hertz at maximum engine load.

1. The engine is cranking or running.
2. The engine speed is more than 50 RPM.
3. The ignition 1 signal is more than 8 volts.
4. The TP indicated angle parameter is more than 3.5 percent.
5. The above conditions are met for more than 0.5 second.

P0102

The control module detects that the MAF sensor frequency signal is less than 1,200 Hertz for more than 10 seconds.

P0103

The control module detects that the MAF sensor frequency signal is more than 11,500 Hertz for more than 10 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components: The secondary ignition wires or coils Any solenoids Any relays Any motors
2. A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 3-10 g/s at idle to 150 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
3. A high resistance may cause a driveability concern before this DTC sets.

J 38522 Variable Signal Generator

Engine Controls Schematics

1. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)
2. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

1. Inspect for any contamination, water intrusion or debris on the sensing elements of the MAF sensor. If debris is present, clean the sensor. If the sensor cannot be cleaned, replace the sensor.
2. Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor. If the fuse is open, test the ignition 1 voltage circuit for a short to ground.
3. Turn OFF the ignition. Disconnect the MAF/intake air temperature (IAT) sensor. Start the engine.
4. Observe the MAF/IAT sensor with a scan tool for 0 Hz. If more than 0 Hz, turn OFF the ignition and inspect the harness for improper routing that is too close to any aftermarket accessories, secondary ignition wires, coils, solenoids, relays or motors.
5. Turn ON the ignition, with the engine OFF.
6. Measure the battery voltage with a DMM.
7. Disconnect the MAF/IAT sensor.
8. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground.
9. Connect the DMM to the probe of the test lamp and good ground and measure for battery voltage. If not within 0.5 volt of battery voltage, repair the high resistance or open in the MAF sensor ignition 1 voltage circuit.
10. Turn OFF the ignition and all accessories for 60 seconds to allow the control module to power down.
11. Measure for 5 ohms of resistance from the ground circuit of the MAF sensor to a good ground with a DMM. If the resistance is more than 5 ohms, repair the high resistance or the open in the MAF sensor ground circuit.
12. Turn ON the ignition, with the engine OFF.
13. Measure for 4.8-5.2 volts from the signal circuit of the MAF sensor to a good ground with a DMM. If more than 5.2 volts, test the circuit for a short to voltage or faulty control module. If less than 4.8 volts, test the circuit for an open, short to ground or a faulty control module.
14. Turn OFF the ignition and connect the J 38522 to the signal circuit of the MAF sensor and a good ground.
15. Set up the variable speed generator. Use the switches to set the duty cycle to normal, the frequency to 5 K and the signal switch to 5 volts.
16. Start the engine and observe the MAF sensor parameter for 4,950-5,025 Hz with a scan tool. If the MAF sensor is not within the specified parameter range, test for intermittent or poor connection at the control module. If tests OK, replace the control module. If the MAF sensor is within the specified parameter range, test for intermittent or poor connection at the MAF sensor. If tests OK, replace the MAF sensor.

1. «Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
2. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for control module replacement, setup and programming

DTC P0107, P0108, P1106 or P1107

Typical Scan Tool Data

MAP Sensor

The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits

1. 5-volt reference circuit
2. Low reference circuit
3. MAP sensor signal circuit

The control module supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The control module also provides a ground on the low reference circuit. The MAP sensor provides a signal to the control module on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The control module should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The control module should detect a high signal voltage at a high MAP, such as the ignition is ON, with the engine OFF or at a wide open throttle (WOT). The MAP sensor is also used in order to determine the barometric pressure (BARO). This occurs when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The control module monitors the MAP sensor signal for voltage outside of the normal range.

P0107 or P1107

1. DTCs P0068, P0120, P0220, P1516, P2101, P2108, P2120, P2125, P2135 or P2138 are not set
2. The ignition is ON.
3. The throttle angle is more than 0 percent, if the engine speed is less than 1,000 RPM. OR
4. The throttle angle is more than 10 percent, if the engine speed is more than 1,000 RPM.

P0108 or P1106

1. DTC P0068, P0120, P0220, P1516, P2101, P2108, P2120, P2125, P2135, P2138 are not set.
2. The engine has been running for a length of time that is determined by the startup coolant temperature. The length of time ranges from 5.5 minutes at less than -30°C (-22°F) to 10 seconds at more than +30°C (+86°F).
3. The throttle angle is less than 2 percent when the engine speed is less than 3,000 RPM. OR
4. The throttle angle is more than 30 percent when the engine speed is more than 3,000 RPM.

P0107

1. The control module detects that the MAP sensor voltage is less than 0.1 volt for more than 3 seconds.
2. This diagnostic runs continuously.

P0108

1. The control module detects that the MAP sensor voltage is more than 4.3 volts for more than 3 seconds.
2. This diagnostic runs continuously.

P1106

1. The control module detects that the MAP sensor voltage is intermittently more than 4.3 volts.
2. This diagnostic runs continuously.

P1107

1. The control module detects that the MAP sensor voltage is intermittently less than 0.1 volt.
2. This diagnostic runs continuously.

P0107 and P0108

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

P1106 and P1107

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

P0107 or P0108

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

P1106 or P1107

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

Engine Controls Schematics

1. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)
2. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

Always perform the Diagnostic System Check - Vehicle .

1. Start the engine.
2. Monitor the DTC information with the scan tool.
3. If DTC P0641 or P0651 is also set, then correct DTC P0641 or P0651 first.
4. With the ignition ON and the engine OFF
5. Disconnect the MAP sensor.
6. Measure for 4.8-5.2 volts from the 5-volt reference circuit of the MAP sensor to a good ground, with a DMM. If more than specified value, then test the circuit for a short to voltage or faulty control module. If less than specified value, then test the circuit for high resistance, an open or an intermittent and poor connection or at the control module or a faulty control module.
7. Disconnect the MAP sensor.
8. Use a scan tool and observe the MAP sensor for less than 12 kPa. If the MAP sensor is more than 12 kPa, then test the MAP sensor signal circuit for a short to voltage or a faulty control module.
9. Use a 3-amp fused jumper wire and connect it between the MAP sensor 5-volt reference circuit and the MAP sensor signal circuit.
10. Use a scan tool and observe the MAP sensor for more than 103 kPa. If the MAP sensor is less than 103 kPa, then test the MAP sensor signal circuit for high resistance or a faulty control module.
11. With the 3-amp fused jumper wire still connected between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor, observe the MAP sensor parameter with the scan tool for 4.9 volts. If more than 4.9 volts, then replace the MAP sensor. If less than 4.9 volts then test the MAP sensor signal circuit between the control module and the MAP sensor for a short to ground, an open or high resistance. Test for an intermittent and for a poor connection at the control module. If tests OK then replace the control module.
12. Turn OFF the ignition and allow the control module to power down.
13. With a DMM, measure for less than 5 ohms of resistance between the low reference circuit of the MAP sensor and a good ground. If the resistance is more than 5 ohms, then test the circuit for a high resistance or a faulty control module.
14. If the MAP sensor circuits test normal, then replace the MAP sensor.

1. «Manifold Absolute Pressure (MAP) Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__manifold-absolute-pressure-map-sensor-replacement)
2. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references)

Diagnostic Repair Verification

DTC P0112, P0113, P1111 or P1112

IAT Sensor Temperature

The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The control module supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the control module detects a high voltage on the IAT signal circuit. With lower sensor resistance, the control module detects a lower voltage on the IAT signal circuit. If the control module detects an excessively low IAT signal voltage, indicating a high temperature, DTC P0112 sets. If the control module detects an excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets. If the control module detects an intermittent high IAT signal voltage, indicating a low temperature, DTC P1111 sets. If the control module detects an intermittent low IAT signal voltage, indicating a high temperature, DTC P1112 sets.

P0112

1. DTCs P0116, P0117, P0118, P0125-L32 only, P0128, P0502, P0503 are not set.
2. The engine run time is more than 10 seconds.
3. The vehicle speed sensor (VSS) indicates that vehicle speed is more than 40 km/h (25 mph).
4. The engine coolant temperature (ECT) is less than 121°C (250°F).
5. The diagnostic runs continuously when the above conditions are met.

P0113

1. DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0125-L32 only, P0128, P0502, P0503 are not set.
2. The engine run time is more than 180 seconds.
3. The VSS indicates that vehicle speed is less than 24 km/h (15 mph).
4. The mass air flow (MAF) is less than 10 g/s.
5. The ECT is more than 60°C (140°F).
6. The diagnostic runs continuously when the above conditions are met.

P1111

1. DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0125-L32 only, P0128, P0502, P0503 are not set.
2. The engine run time is more than 180 seconds.
3. The ECT sensor parameter is more than 60°C (140°F).
4. The vehicle speed is less than 24 km/h (15 mph).
5. The MAF is less than 10 g/s.
6. The diagnostic runs continuously when the above conditions are met.

P1112

1. DTCs P0116, P0117, P0118, P0125-L32 only, P0128, P0502, P0503 are not set.
2. The engine run time is more than 10 seconds.
3. The ECT sensor parameter is less than 121°C (250°F).
4. The VSS indicates that vehicle speed is more than 40 km/h (25 mph).
5. The diagnostic runs continuously when the above conditions are met.

The control module detects that the IAT sensor parameter is more than 130°C (266°F) for more than 18 seconds.

The control module detects that the IAT sensor parameter is less than -36°C (-33°F) for more than 110 seconds.

The control module detects that the IAT sensor parameter is less than -36°C (-33°F) intermittently for more than 100 seconds.

The control module detects that the IAT sensor parameter is more than 130°C (266°F) intermittently for more than 16 seconds.

P0112 and P0113

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

P1112 and P1111

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The MIL will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center (DIC), if equipped, may display a message.

P0112 or P0113

1. The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

P1112 or P1111

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

When the vehicle is at ambient temperature, the IAT sensor and the ECT sensor should be relatively close to each other. Refer to Temperature vs Resistance .

Engine Controls Schematics

1. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)
2. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

Always perform the Diagnostic System Check - Vehicle .

P0112 or P1112

1. Observe the IAT sensor with a scan tool for 130°C (266°F).
2. Disconnect the MAF/IAT sensor. Observe the IAT sensor with a scan tool for -36°C (-33°F). If more than specified temperature, then test the signal circuit of the IAT sensor for a short to ground or a short to the IAT low reference circuit and repair as necessary. Test for an intermittent and for a poor connection at the control module. If all circuits test OK then replace the control module. If less than specified temperature, then test for an intermittent and for a poor connection at the IAT sensor. If circuit tests OK then replace the MAF/IAT sensor.

P0113 or P1111

1. Turn ON the ignition, with the engine OFF. Disconnect the MAF/IAT sensor. Connect a DMM between the signal circuit of the IAT sensor and a good ground. Measure for 5.2 volts. If more than 5.2 volts, then test the signal circuit for a short to voltage.
2. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and the low reference circuit of the IAT sensor. Observe the IAT sensor parameter with a scan tool for 130°C (266°F). If more than 130°C (266°F), then test the IAT signal circuit for a short to any 5-volt reference circuit or for an intermittent and for a poor connection at the IAT sensor. If circuits test OK, then replace the MAF/IAT sensor.
3. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and a good ground. Observe the IAT sensor parameter with a scan tool for 130°C (266°F). If more than 130°C (266°F), then test the IAT sensor low reference circuit for high resistance or for an open. Test for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.

1. «Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
2. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for PCM replacement, setup and programming.

Diagnostic Repair Verification

DTC P0116, P0125 or P0128

ECT Sensor Temperature

P0116

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The control module supplies 5 volts to the signal circuit and a ground for the ECT low reference circuit. When the ECT is low, the sensor resistance is high. When the ECT is high, the sensor resistance is low. The control module uses this High Side Coolant Rationality test to determine if the ECT input is skewed high. The internal clock of the control module will record the amount of time the ignition is OFF. At restart, the control module will compare the temperature difference between the ECT and the intake air temperature (IAT). Before failing this test, the control module will perform a calculation to determine the presence of an engine block heater. If the control module detects that the temperature difference between the ECT and the IAT is not within the calibrated range after the ignition OFF time, DTC P0116 sets.

P0125-L32 only

An ECT sensor monitors the temperature of the coolant. This input is used by the control module for engine control and as an enabling criteria for some diagnostics. The air flow into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the Closed Loop temperature. If the coolant temperature does not increase normally or does not reach the Closed Loop temperature, the diagnostics that use engine coolant temperature as enabling criteria may not run when expected. If the control module detects the calibrated amount of air flow and engine run time have been met and the engine coolant has not met the Closed Loop temperature, DTC P0125 sets.

P0128

An ECT sensor monitors the temperature of the coolant. This input is used by the control module for engine control and as an enabling criteria for some diagnostics. The air flow coming into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat, the diagnostics that use ECT as enabling criteria may not run when expected. If the control module detects the calibrated amount of air flow and engine run time have been met and the ECT has not met the minimum thermostat regulating temperature, DTC P0128 sets.

1. DTCs P0112, P0113, P0117, P0118, P0502, P0503, P0601, P0602, P0604, P0606, P2610 are not set.
2. The ignition is ON.
3. The IAT Sensor parameter is more than 15°C (59°F).
4. The Fuel Level Sensor parameter is more than 10 percent.
5. The vehicle has a minimum ignition OFF time of 8 hours.
6. This diagnostic runs once per ignition cycle when the above conditions are met.

1. DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0502 or P0503 are not set.
2. The minimum air temperature is more than -7°C (+19°F).
3. The start-up ECT is less than 10°C (50°F).
4. The engine run time is between 30-1,800 seconds.
5. The vehicle has traveled more than 0.8 kilometer (0.5 mile) at more than 8 km/h (5 mph).
6. This diagnostic runs once per ignition cycle when the above conditions are met.

1. DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0502 or P0503 are not present.
2. The startup ECT is less than 75°C (167°F).
3. The intake air temperature (IAT) is more than -7°C (+19°F).
4. The engine run time is between 30-1,800 seconds.
5. The vehicle is driven more than 0.8 kilometer (0.5 mile) at more than 8 km/h (5 mph).
6. This diagnostic runs once per ignition cycle when the above conditions are met.

1. The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 100°C (180°F) at start up. OR
2. The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F) and the time elapsed cranking the engine without starting is more than 5 seconds. OR
3. The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F). The vehicle must then be driven for 5 minutes over 40 km/h (25 mph). If the IAT sensor temperature decreases more than 5°C (9°F), an engine block heater was detected and the test is aborted. If the IAT sensor temperature does not decrease, an engine block heater was not detected and DTC P0116 will set.

The control module detects that the actual amount of accumulated airflow is more than the predicted amount of accumulated air flow before the ECT reaches 15°C (59°F).

The control module detects that the actual amount of accumulated air flow is more than the predicted amount of accumulated air flow before the ECT reaches 80°C (176°F).

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Engine Controls Schematics

1. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)
2. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

Scan Tool Reference

Scan Tool Snapshot Procedure

1. Inspect the cooling system coolant level. If low, then refer to «Loss of Coolant»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system__loss-of-coolant) .
2. Observe and record the ambient air temperature of the vehicle environment using an accurate thermometer.
3. After the vehicle has been OFF for 8 hours, remove the mass air flow (MAF)/IAT sensor.
4. Remove the ECT sensor.
5. Place the sensors on a work surface away from any heat source. Allow the sensors to reach the ambient air temperature for 30-60 minutes.
6. Connect the MAF/IAT sensor and the ECT sensor to the electrical connector, but DO NOT install them. Insulate the sensors from any engine heat source.
7. Turn ON the ignition and take a snapshot of the Engine Data List with a scan tool. Refer to «Scan Tool Snapshot Procedure»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .
8. Review the snapshot data that was taken with the scan tool. Observe the ECT Sensor and IAT Sensor parameters with a scan tool. The difference between the ECT Sensor parameter and the IAT Sensor parameter should be more than 15°C (27°F). If less than 15°C (27°F), then refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .
9. Observe the recorded IAT Sensor and ECT sensor parameters. The difference between the IAT Sensor, ECT Sensor parameters and the ambient air temperature should be less than 8°C (14°F). If less than 8°C (14°F), refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .
10. Disconnect the MAF/IAT sensor. Test for an intermittent and for a poor connection at the IAT sensor. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .
11. At the sensor, measure the resistance between the IAT signal and the IAT low reference terminals with a DMM and record the value. Observe the recorded ambient air temperature. Compare the resistance measurement of the IAT sensor to the ambient air temperature using the «Temperature vs Resistance»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__temperature-vs-resistance) . If not within specified range, then replace the MAF/IAT sensor.
12. Disconnect the ECT sensor and inspect for the ECT sensor leaking engine coolant internally through the sensor, corrosion on the ECT sensor terminals or for corrosion on the ECT harness connector terminals.
13. At the sensor, measure the resistance between the ECT signal and the ECT low reference terminals with a DMM and record the value. Observe the recorded ambient air temperature. Compare the resistance measurement of the ECT sensor to the ambient air temperature using the «Temperature vs Resistance»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__temperature-vs-resistance) . If not within specified range, then replace the ECT sensor.
14. Measure for 4.8-5.2 volts from the IAT signal circuit to a good ground with a DMM. If not within specified range, then test the IAT signal circuit for a high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.
15. Turn OFF the ignition for 90 seconds to allow the control modules to power down.
16. Measure for 4.8-5.2 volts from the ECT signal circuit to a good ground with a DMM. If within the specified range, then go to intermittent conditions. If NOT within specified range, then test the ECT signal circuit for a high resistance or short to ground or for shorted terminals and poor connections at the control module. If circuits test OK, then replace the control module.
17. Measure for 5 ohms of resistance from the low reference circuit of the IAT sensor to a good ground with a DMM. If less than 5 ohms, then go to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) . If more then 5 ohms, then test the IAT low reference circuit for high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.

P0125-L32 only or P0128

1. Inspect the cooling system coolant level. If low, then refer to «Loss of Coolant»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system__loss-of-coolant) .
2. Inspect for the following conditions: Corrosion on the ECT terminals Improper or corroded terminals at the ECT harness connector Loose terminals in the ECT harness connector
3. Measure for 4.8-5.2 volts from the signal circuit of the ECT sensor to a good ground with a DMM. If not within specified range, test the ECT sensor signal circuit for high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.
4. Measure for 4.8-5.2 volts from the signal circuit of the ECT sensor to the low reference circuit of the ECT sensor with a DMM. If not within specified range, test the ECT sensor low reference circuit for high resistance or for an intermittent and for a poor connection at the control module. If circuits test OK, then replace the control module.
5. Turn OFF the ignition. Remove the ECT sensor. Place the sensor on a work surface away from any heat source.
6. Allow the sensor to reach ambient air temperature for 30-60 minutes.
7. Observe and record the ambient air temperature of the vehicle environment using an accurate thermometer.
8. At the sensor, measure the resistance between the ECT signal and the ECT low reference terminals with a DMM and record the value.
9. Compare the resistance measurement of the ECT sensor to the ambient air temperature on the «Temperature vs Resistance»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__temperature-vs-resistance) . If within the specified range, then install the ECT sensor and refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) . If NOT within the specified range, then replace the ECT sensor.

1. «Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
2. «Engine Coolant Temperature (ECT) Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
3. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for PCM replacement, setup and programming

Diagnostic Repair Verification

DTC P0117, P0118, P1114 or P1115

ECT Sensor Temperatures

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The control module supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the control module detects a high voltage on the ECT signal circuit. With lower sensor resistance, the control module detects a lower voltage on the ECT signal circuit.

P0117 or P1114

1. The engine run time is more than 3 seconds. OR
2. The ignition is ON and the intake air temperature (IAT) is less than 90°C (194°F).
3. The diagnostic runs continuously when the above conditions are met.

P0118 or P1115

1. The engine is running for more than 30 seconds. OR
2. The ignition is ON and the IAT is more than 0°C (32°F).
3. The diagnostic runs continuously when the above conditions are met.

P0117

The control module detects that the ECT sensor parameter is more than 139°C (282°F) for more than 24 seconds.

P0118

The control module detects that the ECT sensor parameter is less than -37°C (-35°F) for more than 24 seconds.

P1114

The control module detects that the ECT sensor parameter is more than 139°C (282°F) intermittently for more than 20 seconds.

P1115

The control module detects that the ECT sensor parameter is less than -37°C (-35°F) intermittently for more than 20 seconds.

P0117 and P0118

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

P1114 and P1115

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The MIL will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center (DIC), if equipped, may display a message.

P0117 or P0118

1. The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

P1114 or P1115

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

1. An overheating condition may cause this DTC to set.
2. After starting the engine, the ECT sensor temperature should rise steadily to about 90°C (194°F) then stabilize after the thermostat opens.
3. If a short to a separate voltage source occurs, this DTC may set and damage the ECT sensor.
4. If an intermittent condition is suspected, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

Engine Controls Schematics

1. «Engine Controls Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__engine-controls-connector-end-views)
2. «Powertrain Control Module (PCM) Connector End Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__powertrain-control-module-pcm-connector-end)

1. «Circuit Testing»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
4. «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)
5. «Using Fused Jumper Wires»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)
6. «Inducing Intermittent Fault Conditions»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing)

Did you perform the Diagnostic System Check - Vehicle ?

Ignition ON, engine OFF, disconnect the ECT sensor and observe the ECT parameter for -38°C (-36°F).

1. If over -38°C (-36°F), test the signal circuit of the ECT sensor for a short to ground or a short to any low reference circuit or an intermittent and poor connection at the control module. If it checks good, then replace the ECT sensor.
2. If under -38°C (-36°F), test for an intermittent and for a poor connection at the ECT sensor. If it checks good, then replace the control module.

1. With the ignition ON, engine OFF, disconnect the ECT sensor and measure for 5.2 volts from the signal circuit of the ECT sensor to a good round with a DMM. If over 5.2 volts, then test the ECT signal circuit for a short to voltage and test for an intermittent and for a poor connection at the control module. If all test OK, then replace the control module. If under 5.2 volts, then test the signal circuit, low reference circuit, of the ECT sensor for high resistance or an open or a short to any 5-volt reference circuit. If tests OK, then replace the ECT sensor.
2. With the ignition ON, engine OFF
3. Connect a 3-amp jumper wire between the signal circuit of the ECT sensor and the low reference circuit.
4. Observe the ECT parameter with a scan tool for 139°C (282°F). If more then specified value, then test the ECT signal circuit for a short to any 5-volt reference circuit, faulty connection at control module. If circuits test OK, then replace the ECT sensor.
5. Connect a 3-amp jumper wire between the signal circuit of the ECT sensor and a good ground.
6. Observe the ECT parameter with a scan tool for 139°C (282°F). If more than the specified value, then test the ECT low reference circuit for high resistance or an open. Test for a faulty connection at the control module or a faulty control module. If the circuit tests OK, then replace the control module. If less than the specified value, then test the signal circuit of the ECT sensor for high resistance or an open. Test for a faulty connection at the control module or a faulty control module. If the circuit tests OK, then replace the control module.

1. Observe the engine coolant temperature (ECT) sensor parameter on the scan tool, while moving the ECT sensor connector and the control module connector. Is there an abrupt change indicated on the scan tool? If change, then repair the connector or terminal as necessary. If no change, observe the engine coolant temperature (ECT) sensor parameter on the scan tool, while moving the wiring harness at the ECT sensor and the control module. If there is a change on the scan tool, then repair the wiring as necessary.
2. If everything checks out, then refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

1. «Engine Coolant Temperature (ECT) Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
2. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for PCM replacement, setup and programming

Diagnostic Repair Verification

The throttle body assembly contains the following components

1. The throttle blade
2. The throttle actuator motor
3. The throttle position (TP) sensor 1 and 2
4. The throttle actuator control (TAC) module

The TAC system monitors the throttle position with 2 sensors. If the powertrain control module (PCM) receives a message from the TAC module that indicates TP sensor 1 voltage is outside a predetermined range, DTC P0120 will set.

DTC Descriptors

This diagnostic procedure supports the following DTC

DTC P0120 Throttle Position (TP) Sensor 1 Circuit

1. DTCs P0606, P2108 and U0107 are not set.
2. The ignition switch is in the crank or the run position.
3. The ignition voltage is more than 5.23 volts.
4. The communications between the TAC module and the PCM must be valid.

1. The TP sensor 1 voltage is less than 0.376 volts or more than 4.506 volts.
2. The PCM learns a minimum throttle position of more than 0.714 volts.
3. The TP sensor reference voltage is less than 4.54 volts or more than 5.21 volts.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0120

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms, once per second. when the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms, once per second.

If the PCM detects that the HO2S 1 voltage remains below a calibrated amount for an excessive amount of time, DTC P0131 will set.

The HO2S 1 has the following circuits

1. A HO2S 1 high signal circuit
2. A HO2S 1 low reference circuit
3. A HO2S 1 heater ignition voltage circuit
4. A HO2S 1 heater low control circuit

This diagnostic procedure support the following DTC

DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1

The following conditions must first be met

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0201, P0202, P0203, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0454, P0455, P0464, P0496 are not set.
2. DTCs P0401, P0420 and P2A01 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The Air Fuel Ratio parameter is between 12:1-16.5:1.
6. The TP sensor parameter is between 4-40 percent.
7. When not in the power enrichment (PE) mode, the following conditions must also be met: The Air Fuel Ratio parameter is between 12:1-16.5:1. The TP sensor parameter is between 4-40 percent. Loop Status parameter is closed. The ECT parameter is less than 131°C (267°F). All fuel injectors are ON. Traction control is not active.
8. During PE mode, the following conditions must also be met: Engine Run Time parameter is more than 5 minutes. The Air Fuel Ratio parameter is more than 16.5:1. The above conditions are present for at least 2 seconds.

1. The PCM detects that the HO2S 1 signal voltage is less than 78 mV for more than 51 seconds. OR The PCM detects that the HO2S 1 signal voltage is less than 598 mV during PE mode for more than 7.5 seconds.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0131

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 milliseconds, once per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 milliseconds, once per second.

If the PCM detects that the HO2S B1 S1 voltage remains above a calibrated voltage for an excessive amount of time, the following DTCs will set

DTC P0132 for bank 1 sensor 1

The HO2S 1 has the following circuits

1. A HO2S 1 high signal circuit
2. A HO2S 1 low reference circuit
3. A HO2S 1 heater ignition voltage circuit
4. A HO2S 1 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1

The following conditions must first be met

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2153 are not set.
2. DTC P0401, P0420 and P2A01 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The TP sensor parameter is between 3-40 percent.
6. The Air Fuel Ratio parameter is between 12:1-16.5:1.
7. The above conditions must be met for at least 3 seconds.

1. The PCM detects that the HO2S 1 signal voltage is more than 889 mV for more than 75 seconds.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0132

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

If the PCM detects that the HO2S 1 voltage average response time is too slow, DTC P0133 will set.

The HO2S 1 has the following circuits

1. A HO2S 1 high signal circuit
2. A HO2S 1 low reference circuit
3. A HO2S 1 heater ignition 1 voltage circuit
4. A HO2S 1 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0133 HO2S Slow Response Bank 1 Sensor 1

1. DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0131, P0132, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P2A01, P0401 and P0420 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The HO2S 1 heater parameter is ON.
6. The ECT sensor parameter is more than 65°C (149°F)
7. The Engine Run Time parameter is more than 60 seconds.
8. The vehicle is not in PARK, REVERSE or NEUTRAL.
9. The Loop Status parameter is closed.
10. The MAF sensor parameter is between 15-30 g/s.
11. The TP Indicated Angle Parameter is more than 2 percent.
12. The Engine Speed parameter is between 1,200-2,200 RPM.
13. The EVAP System is purging.
14. The above conditions have been met for 1 second.

1. The PCM detects that the HO2S 1 rich-to-lean and lean-to-rich transition time takes longer than a calibrated value.
2. This diagnostic runs once per trip.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0133

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

If the PCM detects that the HO2S 1 voltage remains at or near the bias voltage amount, DTC P0134 will set.

The HO2S 1 has the following circuits

1. A HO2S 1 high signal circuit
2. A HO2S 1 low reference circuit
3. A HO2S 1 heater ignition voltage circuit
4. A HO2S 1 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1

1. DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P0401, P0420 and P2A01 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The HO2S 1 heater parameter is ON.
6. The Engine Run Time parameter is more than 2 minutes.

1. The PCM detects that the HO2S 1 signal voltage is between 382 mV and 525 mV for more than 30 seconds.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0134

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 milliseconds, once per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 milliseconds, once per second.

If the PCM detects that the HO2S 1 heater low control circuit current level is not within the calibrated range, DTC P0135 will set.

The HO2S 1 has the following circuits

1. A HO2S 1 high signal circuit
2. A HO2S 1 low reference circuit
3. A HO2S 1 heater ignition voltage circuit
4. A HO2S 1 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0135 HO2S Heater Performance Bank 1 Sensor 1

The following conditions must be met

1. DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P2A01, P0401, P0420 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The Engine Run Time parameter is more than 100 seconds.
6. The ECT Sensor parameter is at least 65°C (149°F).
7. The MAF sensor parameter is between 4-30 g/s.
8. The Engine Speed parameter is between 600-3,000 RPM.
9. The above conditions have been met for at least 2 seconds.

1. The HO2S heater current is less than 0.31 amp or more than 1.43 amps for at least 17 out of 20 samples. Five tests during each trip with a 30 second delay between each test.
2. Each test duration is 1 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0135

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 milliseconds, once per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 milliseconds, once per second.

If the PCM detects that the HO2S 2 voltage remains below a calibrated voltage for an excessive amount of time, DTC P0137 will set.

The HO2S 2 has the following circuits

1. An HO2S 2 high signal circuit
2. An HO2S 2 low signal circuit
3. An HO2S 2 heater ignition voltage circuit
4. An HO2S 2 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P2A01, P0401 and P0420 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The TP Sensor parameter is between 4-40 percent.
6. The ECT Sensor parameter is less than 131°C (268°F).
7. The Air Fuel Ratio parameter is between 12:1-16.5:1.
8. The Loop Status parameter is closed.
9. All fuel injectors are ON.
10. Traction Control is not active.
11. The above conditions have been met for at least 3 seconds.

1. The PCM detects that the HO2S 2 signal voltage remains below 78 mV for more than 2 minutes.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

This DTC may set due to poor idle characteristics. A possible cause may be uncontrolled fueling due to an open or high resistance in the HO2S 1 low signal circuit. Before replacing any component, ensure that this condition does not exist.

DTC P0137

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 milliseconds, once per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 milliseconds, once per second.

If the PCM detects that the HO2S 2 voltage remains above a calibrated voltage for an excessive amount of time, DTC P0138 will set.

Each HO2S 2 has the following circuits

1. An HO2S 2 high signal circuit
2. An HO2S 2 low signal circuit
3. An HO2S 2 heater ignition voltage circuit
4. An HO2S 2 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2

The following conditions must be met

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P2A01, P0401 and P0420 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The TP Sensor parameter is between 3 percent and 40 percent.
6. The Air Fuel Ratio parameter is between 12:1 and 16.5:1.
7. The Loop Status parameter is closed.
8. The above conditions must be met for at least 3 seconds.

1. The HO2S 2 voltage is more than 924 mV for at least 540 out of 600 samples for 2 sets of samples. Each sample is 100 ms.
2. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0138

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an open loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

If the PCM detects that the HO2S 2 voltage remains at or near the bias voltage, DTC P0140 will set.

Each HO2S 2 has the following circuits

1. An HO2S 2 high signal circuit
2. An HO2S 2 low signal circuit
3. An HO2S 2 heater ignition voltage circuit
4. An HO2S 2 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2

The following conditions must be met

1. DTCs P0036, P0054, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P2A01, P0401 and P0420 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.

This vehicle has 2 methods to enable and run this diagnostic, called regular test and fast pass test.

Fast Pass Test

1. The Engine Run Time parameter is less than 1 minute and 30 seconds. OR
2. A cold start condition has been detected, identified by the following conditions: The Start Up ECT parameter is less than 35°C (95°F). The Start Up IAT parameter is less than 35°C (95°F). The difference between the Start Up ECT parameter and the Start Up IAT parameter is less than 6°C (10.8°F).

Regular Test

If the fast pass test does not report a pass, then the regular test is initiated.

1. The Engine Run Time parameter is more than 2 minutes.
2. The TP Sensor parameter has changed more than 8 percent at least 3 times.
3. The Loop Status parameter is closed.
4. The predicted HO2S temperature is more than 0°C (32°F).

During the fast pass the HO2S 2 voltage is between 381-525 mV and less than 180 samples within the first 1 minute and 30 seconds of engine run time. If the fast pass test does not report a pass then the regular test is initiated.

1. During the regular test the HO2S 2 voltage is between 390-520 mV for at least 1,080 out of 1,200 samples.
2. Each sample is 100 ms during both tests.
3. This diagnostic runs once per trip.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0140

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner. The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms once per second.

If the PCM detects that the HO2S 2 voltage has not changed more than 150 mV from bias voltage within a calibrated amount of time, DTC P0141 will set.

Each HO2S 2 has the following circuits

1. An HO2S 2 high signal circuit
2. An HO2S 2 low reference circuit
3. An HO2S 2 heater ignition voltage circuit
4. An HO2S 2 heater low control circuit

This diagnostic procedure supports the following DTC

DTC P0141 HO2S Heater Performance Bank 1 Sensor 2

1. DTCs P0036, P0054, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125 (where applicable), P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
2. DTCs P2A01, P0401 and P0420 are not commanding fuel.
3. The system voltage is between 9-18 volts.
4. The scan tool special functions are not active.
5. The Engine Run Time parameter is at least 100 seconds.
6. The ECT parameter is at least 65°C (149°F).
7. The MAF Sensor parameter is between 4-30 g/s.
8. The Engine Speed parameter is between 600-3,000 RPM.
9. The above conditions have been met for at least 2 seconds.

1. The HO2S heater current is less than 0.21 A or more than 0.96 A for at least 17 out of 20 test samples.
2. Five test samples during each trip with a 30 second delay between each test.
3. Each test duration is 1 second.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0141

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During Closed Loop the PCM adds oxygen sensor inputs and level of purge to calculate Short and Long Term fuel trim adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. The values for the Short Term fuel trim change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term fuel trim makes coarse adjustments in order to maintain an Air/Fuel Ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and engine load. If the PCM detects an excessively lean condition, DTC P0171 sets.

This diagnostic procedure supports the following DTC

DTC P0171 Fuel Trim System Lean Bank 1

1. DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0120, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0401, P0403, P0404, P0405, P0406, P0420, P0442, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0462, P0463, P0464, P0496, P0506, P0507, P1133, P1134, P1404, P1516, P2101, P2107, P2108, P2119, P2120, P2125, P2135, P2138, P2A00, P2A01 are not set.
2. The engine is in Closed Loop status.
3. Fuel Trim Learn is enabled.
4. The engine coolant is between 38.5-121°C (101.3-250°F).
5. The intake air temperature (IAT) is between -38.5 and +140°C (-37.3 and +284°F).
6. The manifold absolute pressure (MAP) is between 15-99 kPa (2.1-28.8 psi).
7. The vehicle speed is less than 132 km/h (82 mph).
8. The engine speed is between 525-5,600 RPM.
9. The barometric pressure (BARO) is more than 70 kPa (10.1 psi).
10. The idle purge is enabled.
11. The mass air flow (MAF) is between 1-150 g/s.
12. The fuel level is more than 10 percent.
13. The scan tool special functions are not active.

1. The average Long Term fuel trim is above 18.8 percent.
2. The above condition is present for more than 2 minutes.
3. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. The system will go lean if an injector is not supplying enough fuel.
2. A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel.
3. Excessive resistance in the ignition 1 voltage and/or the fuel injector circuits may cause the following symptoms: A lean condition Misfire Rough idle
4. Fuel contamination, such as water and alcohol, will effect the fuel trim.
5. Review the Failure Records with a scan tool. If an intermittent condition is suspected, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .
6. This DTC may set due to poor idle characteristics as a result of uncontrolled fueling caused by an open or high resistance in the HO2S 1 low signal circuit. Before replacing any component ensure that this condition does not exist.

The number below refers to the step number on the diagnostic table.

1. 10: If conditions were not corrected, a worn CAM, worn intake or exhaust valves or other engine mechanical failure may be at fault.

DTC P0171

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During Closed Loop the PCM adds oxygen sensor inputs and level of purge to calculate Short and Long Term fuel trim adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. The values for the Short Term fuel trim change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term fuel trim makes coarse adjustments in order to maintain an Air/Fuel Ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and engine load. The fuel trim diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from the evaporative emission (EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, DTC P0172 sets.

This diagnostic procedure supports the following DTC

DTC P0172 Fuel Trim System Rich Bank 1

1. DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0120, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0401, P0403, P0404, P0405, P0406, P0420, P0442, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0462, P0463, P0464, P0496, P0506, P0507, P1133, P1134, P1404, P1516, P2101, P2107, P2108, P2119, P2120, P2125, P2135, P2138, P2A00, P2A01 are not set.
2. The engine is in Closed Loop status.
3. The Fuel Trim Learn is enabled.
4. The engine coolant is between 38.5-121°C (101.3-250°F).
5. The intake air temperature (IAT) is between -38.5 and +140°C (-37.3 and +284°F).
6. The manifold absolute pressure (MAP) is between 15-99 kPa (2.1-28.8 psi).
7. The vehicle speed is between 13-132 km/h (8-82 mph).
8. The engine speed is between 525-5,600 RPM.
9. The barometric pressure (BARO) is more than 70 kPa (10.1 psi).
10. The idle purge is enabled.
11. The mass air flow (MAF) is between 1-150 g/s.
12. The scan tool special functions are not active.

1. The average Long Term fuel trim value is below -19.5 percent.
2. The above condition is present for more than 2 minutes.
3. This diagnostic runs continuously.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. A malfunctioning MAF sensor can cause a rich condition and set this DTC.
2. If an intermittent condition is suspected, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .
3. This DTC may set due to poor idle characteristics as a result of uncontrolled fueling caused by an open or high resistance in the HO2S 1 low signal circuit. Before replacing any component ensure that this condition does not exist.

The number below refers to the step number on the diagnostic table.

1. 10: If conditions were not corrected, a worn CAM, worn intake or exhaust valves or other engine mechanical failure may be at fault.

DTC P0172

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. The ignition relay supplies an ignition voltage to each fuel injector through an in-line mini-fuse. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. The control module monitors the status of each driver. If the control module detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0201 Injector 1 Control Circuit
2. DTC P0202 Injector 2 Control Circuit
3. DTC P0203 Injector 3 Control Circuit
4. DTC P0204 Injector 4 Control Circuit
5. DTC P0205 Injector 5 Control Circuit
6. DTC P0206 Injector 6 Control Circuit

1. The ignition is ON.
2. The ignition voltage is between 9-18 volts.

1. The powertrain control module (PCM) detects an incorrect voltage on a fuel injector control circuit.
2. The condition exists for 30 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Performing the Fuel Injector Coil Test may help to isolate an intermittent condition. Refer to «Fuel Injector Coil Test»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
2. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) .

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

1. 2: This step isolates the ignition 1 voltage circuit. An open or short to ground in this circuit sets all fuel injector DTCs.
2. 4: This step verifies that the PCM is able to control the fuel injector. If the test lamp flashes, the PCM and wiring are OK.
3. 5: This step tests if a ground is constantly being applied to the fuel injector.

DTC P0201-P0206

See also:
• Diagnostic System Check - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Diagnostic Trouble Code (DTC) List - Vehicle
• Timing Chain and Sprockets Replacement
• Engine Controls Schematics
• Powertrain Control Module (PCM) Connector End Views
• Engine Controls Connector End Views
• Scan Tool Data List
• Circuit Testing
• Wiring Repairs
• Probing Electrical Connectors
• Connector Repairs
• Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice
• Control Module References
• Checking Aftermarket Accessories
• Measuring Voltage Drop
• Diagnostic Repair Verification
• Manifold Absolute Pressure (MAP) Sensor Replacement
• Temperature vs Resistance
• Loss of Coolant
• Silicon Contamination of Heated Oxygen Sensors Notice
• Oil Consumption Diagnosis
• Heated Oxygen and Oxygen Sensor Notice
• Fuel Injector Balance Test with Tech 2
• Altitude vs Barometric Pressure
• Symptoms - Engine Exhaust
• Crankcase Ventilation System Inspection/Diagnosis