Engine Control System - 3.8l - DTC p2125 to DTC u0107 Buick LaCrosse I

Circuit Description

The accelerator pedal position (APP) sensor 2 is a potentiometer type sensor with the following 3 circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 2 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 2 signal or the APP sensor 5-volt reference voltage is outside the predetermined range, DTC P2125 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P2125 Accelerator Pedal Position (APP) Sensor 2 Circuit

Conditions for Running the DTC

1. DTC P2107 is not set.
2. The ignition is ON.
3. The ignition voltage is more than 5.23 volts.

Conditions for Setting the DTC

1. The APP sensor 2 voltage is less than 0.235 volt or more than 4.487 volts. OR
2. The APP sensor 2 5-volt reference voltage is less than 4.54 volts or more than 5.21 volts.

Action Taken When the DTC Sets

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.

Conditions for Clearing the DTC

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.

DTC P2125

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 TP sensor 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 the throttle position, as indicated from TP sensor 1, disagrees with the throttle position indicated from TP sensor 2, DTC P2135 will set.

This diagnostic procedure supports the following DTC

DTC P2135 Throttle Position (TP) Sensor 1-2 Correlation

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

1. The throttle position indicated by TP sensor 1 disagrees with the throttle position indicated by TP sensor 2 by more than 6 percent. OR
2. The PCM learned minimum throttle position of TP sensor 1 disagrees with the learned minimum throttle position of TP sensor 2. OR
3. The PCM detects that the TP sensor 1 signal circuit is shorted to the TP sensor 2 signal circuit.

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.

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.

DTC P2135

The accelerator pedal position (APP) sensor 1 and APP sensor 2 are potentiometer type sensors, each with the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The control module provides the APP sensors a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module signal voltages proportional to pedal movement. The APP sensor 1 and the APP sensor 2 signal voltages are both low at rest and increase as the pedal is depressed. When the control module detects that the APP sensor 1 and the APP sensor 2 signal circuits are out of correlation, DTC P2138 sets.

This diagnostic procedure supports the following DTC

DTC P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation

1. DTCs P2107 and P2108 are not set.
2. The ignition is in the CRANK or RUN position.
3. The ignition voltage is more than 5.23 volts.
4. The communication between the throttle actuator control (TAC) module and the powertrain control module (PCM) must be valid.

The PCM detects that the difference between APP sensor 1 and APP sensor 2 is more than the predicted value.

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.

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.

DTC P2138

System Description

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit.

The AIR diagnostic uses 3 phases to test the AIR system

1. DTCs P0411 and P2430 run during Phase 1
2. DTCs P2430 and P2440 run during Phase 2
3. DTC P2444 runs during Phase 3

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM can detect faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

DTC P2430-The AIR system pressure sensor is stuck range diagnostic monitors the amount of change in the sensor signal during phase 1 and phase 2. When the PCM detects AIR pressure sensor signal change is less than expected DTC P2430 sets. DTC P2430 runs during phase 1 and phase 2.

This diagnostic procedure supports the following DTC

DTC P2430 Secondary Air Injection (AIR) System Pressure Sensor Stuck in Range

1. DTCs P0412, P0418, P0606, P0641, P0651, P2432, P2433 are not set.
2. The system voltage is between 10-18 volts.
3. The engine is running.
4. The start-up engine coolant temperature (ECT) is between 5-50°C (41-122°F).
5. The start-up intake air temperature (IAT) is between 5-60°C (41-140°F).
6. The BARO parameter is more than 60 kPa.
7. The MAF sensor parameter is between 3-24 g/s.
8. DTC P2430 runs once per trip start up when the above conditions are met and AIR pump operation is requested.

1. The measured AIR pressure change does not meet expected pressure changes during AIR pump phase 1 or phase 2 operation.
2. DTC P2430 sets with in 8 seconds when the above conditions are met.

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.

Diagnostic Aids

1. An intermittent malfunction may be caused by a fault in an AIR control/shut-off valve assembly pressure sensor electrical circuits. Inspect the wiring harness and components 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) .
2. If the DTC cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

Test Description

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

1. 5: DTC P2444 will locate and repair the cause of an AIR pump stuck in the ON position.
2. 6: Normal pressure sensor input voltage is approximately 2.6 volts with the ignition ON, the engine OFF and the AIR pump OFF.
3. 13: This step places a known load in the circuit in order to verify proper voltage drop. An appropriate length of secondary ignition wire may be adequate for a fixed 300 ohm resistor.
4. 15: The low reference, the AIR pressure signal, the 5-volt reference circuits and the PCM have tested OK. Replace the AIR control solenoid valve/pressure sensor assembly.

DTC P2430 (L26, NU3)

The DTC P2431 secondary air injection (AIR) system pressure sensor performance diagnostic monitors the accuracy of the sensor signal. The AIR system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit. By comparing the measured pressure against the expected pressure, the PCM can detect faults in the AIR pressure sensors, the AIR pump, the AIR control/shut-off valve and the exhaust check valve. The pressure sensor can also detect leaks in the AIR system plumbing.

This diagnostic procedure supports the following DTC

DTC P2431 Secondary Air Injection (AIR) System Pressure Sensor Performance

1. DTCs P0107, P0108, P0412, P0418, P0606, P0641, P0651, P2432, P2433 are not set.
2. The ignition is ON.
3. DTC P2431 runs continuously when the above conditions are met.

The PCM determines the difference between the AIR pressure sensor and the barometric pressure (BARO) sensor signals is greater than 10 kPa when the AIR pump is commanded OFF.

OR

The PCM determines the difference between the AIR pressure sensor and the BARO sensor signals is greater than 50 kPa when the AIR pump is commanded ON.

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. This DTC may set due to an incorrect manifold absolute pressure (MAP)/BARO value caused by a faulty MAP sensor. Before replacing any component ensure that this condition does not exist.
2. The barometric (BARO) pressure value is initially based on the MAP sensor value at key ON. The BARO value is used to calculate the predicted AIR pressure sensor value.
3. An intermittent malfunction may be caused by a fault in an AIR pressure sensor electrical circuits. Inspect the wiring harness and components 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) .
4. If the DTC cannot be duplicated, the information included in the Freeze Frame can be useful in determining vehicle operating conditions when the DTC was first set.

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

1. 5: If the AIR pump is always ON, DTC P2431 can set. DTC P2444 will locate and repair the cause of an AIR pump stuck in the ON position.
2. 6: This step determines if DTC P2431 is the result of a hard failure or an intermittent condition. Normal pressure sensor input voltage is approximately 2.6 volts with the ignition ON, the engine OFF and the AIR pump OFF.
3. 13: This step places a known load in the circuit in order to verify proper voltage drop. An appropriate length of secondary ignition wire may be adequate for a fixed 300 ohm resistor.
4. 15: The low reference, the AIR pressure signal, the 5-volt reference circuits and the PCM have tested OK. Replace the AIR control solenoid valve/pressure sensor assembly.

DTC P2431 (L26, NU3)

The DTC P2432 secondary air injection (AIR) system pressure sensor circuit low voltage diagnostic monitors the sensor signal for a low voltage. The AIR system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit. By comparing the measured pressure against the expected pressure, the PCM can detect faults in the AIR pump, the AIR control solenoid valve/pressure sensor assembly and the exhaust check valve. The pressure sensor can also detect leaks in the AIR system plumbing.

This diagnostic procedure supports the following DTC

DTC P2432 Secondary Air Injection (AIR) System Pressure Sensor Circuit Low Voltage

1. DTCs P0641, P0651, P0606 are not set.
2. The ignition is ON or the engine is running.
3. DTC P2432 runs continuously when the above conditions are met.

The pressure sensor signal is less than 0.2 volt for at least 12.5 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.

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

1. 5: DTC P2444 will locate and repair the cause of an AIR pump stuck in the ON position.
2. 6: Normal pressure sensor input voltage is approximately 2.6 volts with the ignition ON, the engine OFF and the AIR pump OFF.
3. 13: This step places a known load in the circuit in order to verify proper voltage drop. An appropriate length of secondary ignition wire may be adequate for a fixed 300 ohm resistor.
4. 15: The low reference, the AIR pressure signal, the 5-volt reference circuits and the PCM have tested OK. Replace the AIR control solenoid valve/pressure sensor assembly.

DTC P2432 (L26, NU3)

The DTC P2433 secondary air injection (AIR) system pressure sensor circuit high voltage diagnostic monitors the circuit for a high voltage. The AIR system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit. By comparing the measured pressure against the expected pressure, the PCM can detect faults in the AIR pump, the AIR control/shut-off valve and the exhaust check valve. The pressure sensor can also detect leaks in the AIR system plumbing.

This diagnostic procedure supports the following DTC

DTC P2433 Secondary Air Injection (AIR) System Pressure Sensor Circuit High Voltage

1. DTCs P0641, P0651, P0606 are not set.
2. The ignition is ON or the engine is running.
3. DTC P2433 runs continuously when the above conditions are met.

The pressure sensor signal is more than 4.8 volts for at least 12.5 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.

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

1. 5: DTC P2444 will locate and repair the cause of an AIR pump stuck in the ON position.
2. 6: Normal pressure sensor input voltage is approximately 2.6 volts with the ignition ON, the engine OFF and the AIR pump OFF.
3. 13: This step places a known load in the circuit in order to verify proper voltage drop. An appropriate length of secondary ignition wire may be adequate for a fixed 300 ohm resistor.
4. 15: The low reference, the AIR pressure signal, the 5-volt reference circuits and the PCM have tested OK. Replace the AIR control solenoid valve/pressure sensor assembly.

DTC P2433 (L26, NU3)

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit.

The AIR diagnostic uses 3 phases to test the AIR system

1. DTCs P0411 and P2430 run during Phase 1
2. DTCs P2430 and P2440 run during Phase 2
3. DTC P2444 runs during Phase 3

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM detects faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly and the exhaust check valve. The pressure sensor is also used to detect leaks and restrictions in the secondary AIR system plumbing.

DTC P2440-The AIR control/shut-off valve stuck open diagnostic monitors system airflow. This diagnostic test detects insufficient system pressure due to a malfunctioning AIR control solenoid valve/pressure sensor assembly or AIR valve relay, a malfunctioning AIR pump relay or a restricted or leaking system. When the PCM detects AIR system pressure is too low, DTC P2440 sets. DTC P2440 runs during Phase 2.

1. The AIR system pressure is sufficient and DTC P2440 passes. DTC P2440 AIR diagnostic proceeds to Phase 3.
2. The AIR system pressure is not sufficient. DTC P2440 AIR diagnostic fails, testing is stopped and DTC P2440 sets.

This diagnostic procedure supports the following DTC

DTC P2440 Secondary Air Injection (AIR) Control/Shut-Off Valve Stuck Open

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0201-P0206, P0300, P0350, P0411, P0412, P0418, P0420, P0606, P0641, P0651, P1350, P2430, P2431, P2432, P2433 are not set.
2. The system voltage is between 10-18 volts.
3. The engine is running.
4. The start-up engine coolant temperature (ECT) is between 5-50°C (41-122°F).
5. The start-up intake air temperature (IAT) is between 5-60°C (41-140°F).
6. The BARO parameter is more than 60 kPa.
7. The MAF sensor parameter is between 3-24 g/s.
8. DTC P2440 runs once per trip start up when the above conditions are met and AIR pump operation is requested.

1. The AIR system does not meet expected pressure conditions during AIR pump Phase 2 operation.
2. DTC P2440 sets within 8 seconds when the above conditions are met.

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. This DTC may set if the ignition is turned OFF and the engine is restarted within approximately 30 seconds during Phase 2 of the AIR diagnostic test.
2. Clear the codes and operate the vehicle within the Conditions for Running the DTC.
3. If the condition is determined to be 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) .

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

1. 4: This step tests for a short to battery positive voltage on the AIR control solenoid valve supply voltage circuit.

DTC P2440 (L26, NU3)

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit.

The AIR diagnostic uses 3 phases to test the AIR system

1. DTCs P0411 and P2430 run during Phase 1
2. DTCs P2430 and P2440 run during Phase 2
3. DTC P2444 runs during Phase 3

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM can detect faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

The DTC P2444 Secondary Air Injection (AIR) Pump is Stuck ON diagnostic monitors the system pressure signal during test phase 3. When the PCM determines the AIR pressure sensor signal is higher than expected, DTC P2444 sets.

This diagnostic procedure supports the following DTC

DTC P2444 Secondary Air Injection (AIR) System Pump Stuck On

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0350, P0411, P0412, P0418, P0420, P0606, P0641, P0651, P1350, P2430, P2431, P2432, P2433, P2440 are not set.
2. The system voltage is between 10-18 volts.
3. The engine is running.
4. The start-up engine coolant temperature (ECT) parameter is between 5-50°C (41-122°F).
5. The start-up intake air temperature (IAT) parameter is between 5-60°C (41-140°F).
6. The BARO parameter is more than 60 kPa.
7. The MAF sensor parameter is between 3-24 g/s.
8. DTC P2444 runs once per trip start-up when the above conditions are met and the AIR pump operation is requested.

The measured AIR pressure is more than expected during AIR pump Phase 3 operation. DTC P2444 sets within 5 seconds when the above conditions are met.

1. The PCM illuminates the malfunction indicator lamp (MIL) during the first key cycle in which the diagnostic trouble code (DTC) sets.
2. The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

1. The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using the scan tool Clear Information function.

Inspect for any of the following conditions

1. An AIR pump that fails to turn OFF may set DTC P2431.
2. The AIR pump can be damaged if it fails to turn OFF. Inspect and correct the cause of an inoperable pump before replacing pump.
3. The resistance of the AIR pump relay coil (across terminal 85 and terminal 86) is 50-70 ohms at 20°C (68°F). In the normal unenergized state, the resistance of the open relay contacts (across terminal 30 and terminal 87) is infinite.
4. The AIR pump relays electrical contacts may be pitted and sticking. Replace the relay if tapping gently on the relay or wiggling the relay causes a change in the relays operation.
5. The performance of the AIR pump relay may be affected by temperature. Check the relay after sitting outside overnight and after running the engine 30 minutes.
6. An intermittent malfunction may be caused by a fault in an AIR system electrical circuit. Inspect the wiring harness and components 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. 3: This step tests for the correct operation of the AIR pump. When the AIR pump relay is commanded ON with the scan tool, only the AIR pump relay is energized. When the AIR valve relay is commanded ON with the scan tool, both the AIR pump and the AIR valve relays are energized.
2. 4: This step tests for the correct operation of the AIR pump relay.

DTC P2444 (L26, NU3)

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 provide an accurate voltage signal. If the PCM detects an active HO2S 1 signal of a lower than calibrated minimum amplitude, DTC P2A00 will set for bank 1 sensor 1.

Each HO2S 1 has the following circuits

1. The HO2S 1 high signal circuit
2. The HO2S 1 low signal 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 P2A00 HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 1

1. DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0125 where applicable, P0128, P0131, P0132, P0133, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P1133 and P1134, P2135 are not set.
2. Where applicable, DTCs P0412, P2440, P2444 are not set.
3. The Engine Run Time parameter is at least 3 minutes.
4. The traction control, if equipped, is not active.
5. The PCM is not commanding Power Enrichment or Decel Fuel Cutoff modes.
6. The MAF Sensor parameter is between 5-38 g/s.
7. The Engine Speed parameter is between 602-3,000 RPM.
8. The TP Indicated Angle parameter is between 3-35 percent.
9. The ECT Sensor parameter is more than 65°C (149°F).
10. The system voltage is between 9-18 volts.
11. The above conditions have been met for 3 seconds.

1. The PCM detects that the HO2S 1 voltage signal remains within the 300-600 mV range for more than 3.6 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 P2A00

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. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

The HO2S 2 is used for catalyst monitoring. This diagnostic runs once per valid trip. This diagnostic has 2 phases for running the DTC, a passive test and an intrusive test. If the HO2S 2 voltage transitions below 290 mV and above 685 mV during the passive test, the DTC will pass for this ignition cycle. If the DTC does not pass during the passive test, the powertrain control module (PCM) will wait a calibrated amount of time and then begin the intrusive test. The control module will adjust the air-to-fuel ratio during the intrusive test. As the air-to-fuel ratio is adjusted to rich and lean, the control module waits for a predicted response from the HO2S 2. If the HO2S 2 voltage transitions below 290 mV and above 685 mV, the diagnostic will pass for this ignition cycle. If the control module does not receive the expected response from the HO2S 2, DTC P2A01 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 signal 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 P2A01 HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 2

DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0125, P0128, P0131, P0132, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P1133 and P1134, P2135 are not set.

Passive Test

1. The engine is running for at least 6 seconds.
2. The ignition voltage is between 9-18 volts.

Intrusive Test

1. The Engine Run Time parameter is more than 6.5 minutes.
2. The ignition voltage is between 9-18 volts.
3. The Engine Speed parameter is between 1,000-3,000 RPM.
4. The MAF Sensor parameter is between 15-40 g/s.
5. The Vehicle Speed parameter is between 32-128 km/h (20-80 mph).
6. The exhaust gas recirculation (EGR) flow diagnostic is not active.
7. The evaporative emission (EVAP) purge diagnostic is not active.
8. The Short Term FT Bank 1 or the Short Term FT Bank 2 parameter is between +3.5 and -3.5 percent.
9. The Loop Status parameter is closed.
10. The EVAP purge solenoid is greater than 0 percent.

1. The HO2S 2 parameter is between 290-685 mV during the passive test.
2. One of the following tests fail: Lean Intrusive Test The PCM detects that the HO2S 2 voltage is more than 290 mV for 11.4 seconds. The PCM detects that the HO2S 1 voltage is less than 100 mV. Rich Intrusive Test The PCM detects that the HO2S 2 voltage is less than 685 mV for 11.4 seconds. The PCM detects that the HO2S 1 voltage is more than 777 mV.
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 P2A01

The throttle actuator control (TAC) module and the powertrain control module (PCM) communicate using a dedicated serial data circuit. This serial data circuit is separate from any other serial data circuit on the vehicle. Accurate transmitting and receiving of serial data requires not only good circuit integrity but also adequate system voltage. This diagnostic monitors the accuracy of the serial data transmitted between the TAC module and the PCM. If the PCM detects a loss of data or invalid data or if the throttle limit is exceeded while operating in the Reduced Engine Power mode, DTC U0107 sets.

This diagnostic procedure supports the following DTC

DTC U0107 Throttle Actuator Control (TAC) Module Serial Data Circuit

1. The ignition is in the crank or run position.
2. The ignition voltage is more than 5.23 volts.
3. The communication between the TAC module and the PCM must be valid.

1. Invalid or missing serial data messages are detected for a predetermined period of time OR
2. The throttle limit is exceeded while operating in the Reduced Engine Power mode.

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.

1. DTC U0107 sets if the battery voltage is low or the PCM is replaced or reflashed. If the customer's concern is slow cranking or if the engine is not cranking because the battery voltage is low, ignore DTC U0107. Clear any DTCs from memory that may have set from the low battery voltage condition.
2. 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) .

DTC U0107

See also:
• Engine Controls Schematics
• Powertrain Control Module (PCM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic System Check - Vehicle
• Diagnostic Trouble Code (DTC) List - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Manifold Absolute Pressure (MAP) Sensor Diagnosis
• Control Module References
• Scan Tool Data List
• Silicon Contamination of Heated Oxygen Sensors Notice
• Heated Oxygen and Oxygen Sensor Notice
• Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice
• Probing Electrical Connectors
• DTC P2444 (L26, NU3)