Engine Control System - 3.8l - DTC p0451 to DTC p2120 Buick LaCrosse I

System Description

The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller uses this FTP signal to determine atmospheric pressure for use in the engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference it must first be re-zeroed. If the FTP signal is out of range during the re-zero procedure, this DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P0451 Fuel Tank Pressure (FTP) Sensor Performance

Conditions for Running the DTC

1. DTC P0451 runs only when the engine-off natural vacuum small leak test, DTC P0442, executes.
2. The number of times this test runs can range from 0-2 per engine-off period. The length of the test can be up to 10 minutes.

Conditions for Setting the DTC

This DTC will set if the controller is unable to re-zero the FTP sensor voltage within a calibrated range during the engine-off small leak test, P0442.

Action Taken When the DTC Sets

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/Failure Records.

Conditions for Clearing the MIL/DTC

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 DTC with a scan tool.

Diagnostic Aids

1. A restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from bleeding off fast enough. If the vent system cannot bleed off pressure fast enough, the re-zero procedure may not complete successfully, which could cause this code to set. By using the purge solenoid command on a scan tool, vacuum can be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the vacuum should not increase to more than 9 inches H2O.
2. Ensure that the reference port on the FTP sensor is unobstructed.

DTC P0451

Circuit Description

The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage goes below a calibrated value, this DTC sets.

The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum.

DTC P0452

This diagnostic procedure supports the following DTC

DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

The ignition is ON.

The FTP sensor voltage is less than 0.1 volt for more than 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.

DTC P0452

The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage increases above a calibrated value, this DTC sets.

The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.

DTC P0453

This diagnostic procedure supports the following DTC

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

The ignition is ON.

The FTP sensor voltage is more than 4.9 volts for more than 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.

Test Description

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

1. 2: If DTC P0651 set, the 5-volt reference circuit may be shorted to a voltage.

DTC P0453

The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. This DTC will set if the control module detects an intermittent signal from the FTP that would prevent the engine-off small leak test, DTC P0442, from running.

This diagnostic procedure supports the following DTC

DTC P0454 Fuel Tank Pressure (FTP) Sensor Circuit Intermittent

1. DTC P0454 runs only when the engine-off natural vacuum small leak test, P0442, executes.
2. This test can run once per engine-off period. The length of the test can be up to 10 minutes.
3. A refueling event is not detected.

If, during the engine-off natural vacuum small leak test, P0442, the engine control module (ECM) detects an abrupt FTP signal change, other than a refueling event, this DTC will set. An abrupt change is defined as a change of 1 inch H2O in the span of 1 second.

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/Failure Records.

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 DTC with a scan tool.

1. This diagnostic is designed to detect an unexpected abrupt voltage signal change from the FTP.
2. Scan tool output controls, snapshot and plot functions can help detect erratic sensor response. To look at the sensor signal under vacuum conditions, use snapshot and the purge/seal function to capture data while commanding purge to 30 percent and then plot the data to look for erratic sensor operation. A similar inspection can be done for the pressure side of the sensor range by applying pressure with the J 41413-200 Evaporative Emissions System Tester (EEST) while taking a snapshot.
3. Ensure that the reference port on the FTP sensor is unobstructed.

DTC P0454

The control module tests the Evaporative Emission (EVAP) System for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge solenoid valve OPEN and the EVAP canister vent solenoid valve CLOSED. This allows engine vacuum to enter the EVAP system. At a calibrated time or vacuum level, the control module commands the EVAP canister purge solenoid valve closed, sealing the system and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level or if the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states and the OPEN or CLOSED states of the EVAP canister purge and vent solenoid valves.

DTC P0455

This diagnostic procedure supports the following DTC

DTC P0455 Evaporative Emission System Large Leak Diagnostic

1. DTC P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0125, P0128, P0443, P0446, P0449, P0452, P0453, P0502, P1111, P1112, P1114, P1115, P1120, P1121, P1122 are not set.
2. The engine is running.
3. The ignition voltage is between 10-18 volts.
4. The barometric pressure (BARO) is more than 75 kPa.
5. The fuel level is between 15-85 percent.
6. The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
7. The intake air temperature (IAT) is between 4-30°C (39-86°F).
8. The start-up ECT and IAT are within 9°C (16°F) of each other.
9. The vehicle speed sensor (VSS) is less than 129 km/h (80 mph).
10. DTC P0455 runs once per cold start when the above conditions are met.

The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.

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. To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15 second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. A temporary blockage in the EVAP canister purge solenoid valve, purge pipe or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system.
3. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
4. Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
5. For intermittent conditions, 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. 6: A normal operating FTP sensor should increase above 5 inches of H2O and stop between 6 inches of H2O and 7 inches of H2O.

DTC P0455

This DTC tests for undesired intake manifold vacuum flow to the evaporative emission (EVAP) system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve OFF and the EVAP canister vent solenoid valve ON. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

DTC P0496

This diagnostic procedure supports the following DTC

DTC P0496 Evaporative Emission System Flow During Non-Purge

1. DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P1106, P1107, P1111, P1112, P1114, P1115, P1125, P1516 are not set.
2. The ignition voltage is between 10-18 volts.
3. The barometric pressure (BARO) is more than 74 kPa.
4. The fuel level is between 15-85 percent.
5. The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
6. The intake air temperature (IAT) is between 4-30°C (39-86°F).
7. The start up ECT and IAT are within 9°C (16°F) of each other.
8. DTC P0496 runs once per drive cycle when the above conditions are met.

The control module detects vacuum during a non-purge condition.

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 P0496

The throttle actuator (TAC) motor is controlled by the TAC module using various inputs from the powertrain control module (PCM) which are communicated across serial data. The DC motor located on the throttle body drives the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed, reducing air flow into the engine. In order to increase idle speed, the TAC module commands the throttle plate open, allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, DTC P0506 sets.

This diagnostic procedure supports the following DTC

DTC P0506 Idle Speed Low

1. DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0171, P0172, P0201-P0206, P0220, P0300, P0401, P0404, P0405, P0443, P0496, P0502, P0503, P1106, P1107, P1111, P1112, P1114, P1115, P1125, P1404, P1516, P2101, P2107, P2108, P2119, P2120, P2125, P2135, P2138 and U0107 are not set.
2. DTCs P0136, P0401 and P0420 have passed.
3. The engine is operating.
4. The engine coolant temperature (ECT) is more than -40°C (-40°F).
5. The intake air temperature (IAT) is more than -40°C (-40°F).
6. The barometric pressure (BARO) is more than 60 kPa.
7. The system voltage is between 11-18 volts.
8. The vehicle speed is less than 4.8 km/h (3 mph).
9. The throttle position (TP) angle is less than 0.25 percent.

1. The difference between the actual and desired idle RPM exceeds a calibrated limit. This limit varies from 300 RPM at -40°C (-40°F) to 100 RPM at 152°C (305°F) based on engine coolant temperature.
2. The above conditions are present for 8 seconds in order for the test to fail. Four tests must fail in order to set this DTC. The vehicle must exit conditions for running between each test.

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 number below refers to the step number in the diagnostic table.

1. 2: This test determines whether the engine can achieve the commanded RPM. If the engine does not reach the commanded RPM, the test determines whether the RPM is too high or too low.

DTC P0506

The throttle actuator control (TAC) motor is controlled by the TAC module using various inputs from the powertrain control module (PCM) which are communicated across serial data. The DC motor located on the throttle body drives the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed, reducing air flow into the engine. In order to increase idle speed, the TAC module commands the throttle plate open, allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, DTC P0507 sets.

This diagnostic procedure supports the following DTC

DTC P0507 Idle Speed High

1. DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0171, P0172, P0201-P0206, P0220, P0300, P0401, P0404, P0405, P0443, P0496, P0502, P0503, P1106, P1107, P1111, P1112, P1114, P1115, P1125, P1404, P1516, P1518, P2101, P2107, P2108, P2119, P2120, P2125, P2135 and P2138 are not set.
2. DTCs P0136, P0401 and P0420 have passed.
3. The engine is operating.
4. The engine coolant temperature (ECT) is more than -40°C (-40°F).
5. The intake air temperature (IAT) is more than -40°C (-40°F).
6. The barometric pressure (BARO) is more than 60 kPa.
7. The system voltage is between 11-18 volts.
8. The vehicle speed is less than 4.8 km/h (3 mph).
9. The throttle position (TP) angle is less than 0.25 percent.

1. The difference between the actual and desired idle RPM exceeds a calibrated limit. This limit varies from 300 RPM at -40°C (-40°F) to 175 RPM at 152°C (305°F) based on ECT.
2. The above conditions must be present for 8 seconds in order for the test to fail. Four tests must fail in order to set this DTC. The vehicle must exit conditions for running between each test.

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 number below refers to the step number in the diagnostic table.

1. 2: This test determines whether the engine can achieve the commanded RPM. If the engine does not reach the commanded RPM, the test determines whether the RPM is too high or too low.

DTC P0507

Description

This diagnostic applies to internal microprocessor integrity conditions within the powertrain control module (PCM) and the throttle actuator control (TAC) system. This diagnostic also addresses if the PCM is not programmed.

The PCM monitors its ability to read and write to the memory. It also monitors a timing function. The PCM and the TAC processors are used to monitor the TAC system data. Both processors monitor the other processors data to verify that the indicated accelerator pedal position (APP) calculation is correct. The PCM performs an intrusive test in order to confirm that the APP signals are not shorted together. The PCM accomplishes this by pulling the APP sensor 2 low momentarily and looking for sensor 1 to also be pulled low.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC P0601 Control Module Read Only Memory (ROM)
2. DTC P0602 Control Module Not Programmed
3. DTC P0604 Control Module Random Access Memory (RAM)
4. DTC P0606 Control Module Internal Performance
5. DTC P2610 Control Module Ignition Off Timer Performance

P0601

The following conditions must be met

1. The ignition switch is in Run or Crank.
2. The system voltage is more than 5 volts.

P0602

The following conditions must be met

1. The ignition switch is in Run or Crank.
2. The controller is identified as a service replacement PCM.

P0604

The ignition switch is in Run or Crank.

P0606

The following conditions must be met

1. The ignition switch is in Run or Crank.
2. During test function after key off before the control module powers down.

P2610

The following condition must be met

1. The ignition switch is in the OFF position for at least 1.6 seconds.
2. A low battery voltage or a battery disconnect condition has not taken place. Ignition OFF timer from the previous ignition cycle is stored.

The PCM checksum value is incorrect for at least one sample. Each sample is 50 milliseconds. The PCM detects that the check sum value is incorrect for 0.05 second. This diagnostic runs continuous.

The PCM has not been programmed with Key On and Engine Off for one sample. Each sample is 100 milliseconds. The PCM has not been programmed at Key On and Engine Off for 0.1 second. This diagnostic runs continuous.

The PCM is unable to correctly write and read to and from random access memory (RAM) during the following conditions

1. Key up initialization for one count. Each count is a read and write sample. Each sample is 100 milliseconds. This portion runs once per ignition cycle.
2. Counter increments by 10 for each sample that does not correctly read and write to the RAM and decrements by one for each correct sample. No more than 20 counts which do not read and or write correctly. Each read and write sample is 100 milliseconds. This portion runs continuously.
3. Counter increments by 10 for each sample that does not correctly read and write to the Desired Throttle Position RAM and decrements by one for each correct sample. No more than 20 counts which do not read and or write correctly. Each read and write sample is 12.5 milliseconds. This portion runs continuously.

The PCM detects that the TAC system has a process sequence error, clock error or processor is not operating correctly. Each test runs in 18.5 milliseconds. DTC sets after 200 milliseconds that a fault is detected.

This diagnostic has 2 tests that may set this DTC

Phase 1

1. The PCM detects the ignition off timer is less than 1 second at any time.
2. The PCM detects the ignition off timer is 15 seconds or more if the actual elapsed time is less than 15 seconds.
3. This diagnostic runs continuous.

Phase 2

1. The last ignition off time event increments more than 1.375 seconds or less than 0.8 seconds for each second.
2. This diagnostic runs continuous.

Actions Taken When DTC Sets

P0601, P0602, P0604 and P0606

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/Failure Records.

P2610

1. The control module illuminates the 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.
3. If the diagnostic reports a failure, the control module uses a cold start model based on the engine coolant temperature and intake air temperature at engine start-up. Using the cold start model ensures that the control module is able to determine how much time has elapsed between ignition cycles.

Conditions for Clearing the MIL/DTC P0601, P0602, P0604, P0606 and P2610

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.

Circuit/System Testing for DTC P0601, P0602, P0604, P0606 and P2610

1. Observe the DTCs with the scan tool. If DTC P0602 is set attempt to program the PCM before replacing the PCM-refer to Service Programming System (SPS) . If DTC P0602 resets, replace the PCM.
2. Test the voltage and ground circuits to the control module for the following conditions: A short An open High resistance

1. If all circuits test OK, replace the PCM.

Repair Procedures

Control Module References for PCM replacement, programming and setup

Diagnostic Fault Information

DTC P0641 or P0651

Circuit/System Description

The control module has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference bus provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference bus. The control module monitors the voltage on the 5-volt reference busses.

The 5-volt reference 1 bus provides 5 volts to the following sensors

1. The manifold absolute pressure (MAP) sensor
2. The fuel tank pressure (FTP) sensor
3. The exhaust gas recirculation (EGR) valve

The 5-volt reference 2 bus provides 5 volts to the Air conditioning (A/C) refrigerant pressure sensor

1. DTCs P0601, P0602, P0604, P0606 and P2610 are not set.
2. The ignition is ON.
3. The ignition voltage is more than 9.5 volts.
4. DTCs P0641 and P0651 run continuously when the above conditions are met.

The control module detects a voltage out of tolerance condition on the 5-volt reference 1 or 2 bus for more than 0.5 second.

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/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.

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)

Scan Tool Reference

Scan Tool Data List

P0641

Observe the MAP sensor voltage parameter with a scan tool with the ignition ON and the engine OFF. The scan tool should display 3.6-4.8 volts for a normally operating system.

P0651

With the ignition ON and the engine OFF, observe the A/C Refrigerant Pressure-A/C High Side Pressure parameter with a scan tool. The scan tool should display 0.2-4.9 volt or 9-453 psi for a normally operating system.

1. With the ignition OFF, disconnect the harness connector at the MAP sensor.
2. With the ignition ON, measure for 4.8-5.2 volts between the MAP sensor 5-volt reference circuit and ground.
3. Command the EGR valve to 100 percent while monitoring the MAP sensor 5-volt reference circuit with a DMM. If within 4.8-5.2 volts, 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. With the ignition OFF, disconnect the harness connector at the EGR valve.
5. With the ignition ON, measure EGR valve 5-volt reference circuit. If within 4.8-5.2 volts, replace the EGR valve. If over 5.2 volts, check for unexpected voltage at each 5-volt reference circuit or the signal circuit for each component associated with the 5-volt reference. If under 4.8 volts, check for a short to ground or low reference circuit at each 5-volt reference circuit.
6. With the ignition ON, use a scan tool to observe the voltage parameter for each component associated with the 5-volt reference circuit while disconnecting each component one at a time. If the data parameters change with any component being disconnected, replace the component.
7. If all circuits tested are OK, replace the control module.

1. With the ignition OFF, disconnect the harness connector at the A/C pressure sensor.
2. With the ignition ON, measure for 4.8-5.2 volts between the A/C pressure sensor 5-volt reference circuit and ground. If within 4.8-5.2 volts, 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 over 5.2 volts, test all 5-volt references circuits for a short to voltage. If all circuits tested are OK, replace the A/C pressure sensor. If under 4.8 volts, turn OFF the ignition and test all 5-volt references circuits for a short to ground or any sensor low reference circuit.
3. If all circuits tested are OK, replace the control module.

1. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
2. «Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
3. «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for engine control module (ECM) replacement, setup and programming
4. «Fuel Tank Pressure Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)
5. «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)

DTC P0650

The malfunction indicator lamp (MIL) is located on the instrument panel cluster (IPC).

The MIL informs the driver that an emission system fault has occurred and that the engine control system requires service. The control module monitors the MIL control circuit for conditions that are incorrect for the commanded states of the MIL.

DTC P0650 runs continuously when the ignition is ON.

The control module detects that the commanded state of the MIL driver and the actual state of the control circuit do not match for more than one 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.

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)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

Circuit/System Verification

Turn ON the ignition, then command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF when commanded.

Circuit/System Testing

1. Turn OFF the ignition.
2. Disconnect the engine control module (ECM).
3. Turn ON the ignition with the engine OFF. If the MIL is still ON, test the MIL control circuit for a short to ground. If the MIL control circuit tested OK and the MIL stayed ON, replace the IPC. If the MIL control circuit tested OK and the MIL went out when the engine control module (ECM) was disconnected, replace the ECM.
4. Measure for 12 volts from the MIL ignition voltage circuit in the IPC harness connector to a ground. If there is less than 12 volts, test the MIL ignition voltage circuit for an open or a short to ground and an open fuse.
5. Remove the fuse that supplies voltage to the MIL.
6. Measure for less than one volt from the MIL control circuit in the ECM harness connector to a good ground. If there is more than one volt, test the MIL control circuit for a short to voltage.
7. Install the fuse that supplies voltage to the MIL.
8. The MIL should illuminate with a 3-amp fused jumper wire connected between the MIL control circuit in the ECM harness connector and a good ground. If the MIL does not illuminate, test the MIL control circuit for an open or high resistance. If the MIL control circuit tests OK, replace the IPC. If the MIL does illuminate, but does not when commanded ON with a scan tool, replace the ECM.

Control Module References for ECM replacement, setup and programming

DTC P0685

Typical Scan Tool Data

EC Ignition Relay Feedback Signal

The powertrain relay is a normally open relay. The relay switch is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the relay switch contact at all times. The engine control module (ECM) supplies the ground path to the relay coil control circuit through an output driver module (ODM). The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the powertrain relay ON, ignition 1 voltage is supplied to the following fuses in the underhood fuse block

1. The ETC Fuse
2. Emission 1 Fuse

The ignition 1 voltage that is supplied to the ECM through the ETC fuse, provides power to the internal ECM circuits associated with the throttle actuator control (TAC) operation. The ECM also monitors the voltage level on the ignition 1 voltage circuit to confirm that the powertrain relay contacts have closed.

1. The battery voltage is between 9-18 volts.
2. The ignition is ON.
3. The powertrain relay has been commanded ON.

1. The commanded state of the ODM does not match and the actual state of the control circuit.
2. The condition is present for more than 5 seconds.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in failure records.

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 this or any other related diagnostic reports no other failures.
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)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

1. This test procedure assumes that the vehicle battery has passed a load test and is completely charged. Refer to «Battery Inspection/Test»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) .
2. When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the mating electrical terminals for correct tension.

1. With the ignition ON, engine OFF, command the powertrain relay ON and OFF several times using the scan tool output control function. You should either hear or feel the relay click with each command.
2. With the ignition ON, engine OFF, probe both test points of each of the following fuses: ETC Fuse Emission 1 Fuse The test lamp should illuminate on at least one test point of each fuse. If the test lamp does not illuminate continue with Circuit/System Testing.

1. With the ignition OFF, remove the powertrain relay from the underhood fuse block.
2. With the ignition ON, measure for battery positive voltage (B+) between the relay coil voltage supply circuit and ground. If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay coil. All wire circuit resistance should measure less than 2 ohms.
3. Measure for voltage between the relay coil control circuit and ground. If voltage is measured on the control circuit of the relay, test for a short to voltage.
4. Connect a test lamp between the battery positive voltage supply circuit of the relay coil and the relay coil control circuit. Use a scan tool to command the powertrain relay ON and OFF. The test lamp should turn ON and OFF when toggling between the commanded states. If the test lamp stays ON all the time, test for a short to ground on the relay coil control circuit or a faulty ECM. If the test lamp stays OFF all the time, test for an open or high resistance on the relay coil control circuit or a faulty ECM. All wire circuit resistance should measure less than 2 ohms.
5. Measure for B+ between the relay armature supply circuit and ground. If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay armature. All wire circuit resistance should measure less than 2 ohms.
6. With the ignition ON, test for voltage on each test point of the ETC fuse. If voltage is present, test the ignition 1 voltage circuit between the ECM, the powertrain relay and the ETC fuse for a short to voltage. If both circuits test normal, replace the ECM.
7. Connect a 20-amp fused jumper wire between the B+ terminal and the ignition 1 voltage terminal of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ETC fuse. If the test lamp illuminates at both test points of the ETC fuse, repair the ignition 1 voltage circuit between the powertrain relay and the ECM for an open, high resistance or a faulty ECM. All wire circuit resistance should measure less than 2 ohms. If the test lamp only illuminates at one test point of the ETC fuse, repair the short to ground in the ignition 1 voltage circuit between the fuse and the applicable component. Replace the fuse, as necessary. If the test lamp does not illuminate on either test point of the ETC fuse, repair the open or high resistance between the powertrain relay and the ETC fuse. All wire circuit resistance should measure 2 ohms or less.
8. With a test lamp, test for voltage on both test points of the following fuses: ETC Fuse Emission 1 Fuse If the test lamp fails to illuminate on one test point of each fuse, repair the open or high resistance between the fuse and the powertrain relay. All wire circuit resistance should measure 2 ohms or less.

Component Testing

1. Measure for 70-110 ohms between terminals 85 and 86 of the relay. If the resistance is not within the specified range, replace the relay.
2. Measure for infinite resistance between terminals 30 and 86 of the relay. If continuity is detected, replace the relay.
3. Measure for infinite resistance between terminals 30 and 87 of the relay. If continuity is detected, replace the relay.
4. Measure for infinite resistance between terminals 30 and 85 of the relay. If continuity is detected, replace the relay.
5. Measure for infinite resistance between terminals 85 and 87 of the relay. If continuity is detected, replace the relay.
6. Connect a 20-amp fused jumper wire from the battery positive cable at the battery, to relay terminal 85. Connect a jumper wire from the negative battery cable at the battery, to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay, with a DMM. If the resistance measures more than 2 ohms, replace the relay.

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine. If engine does not run, refer to «Engine Cranks but Does Not Run»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
4. If other DTCs are set, refer to «Diagnostic System Check - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information) .

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 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is also low at rest and increases as the pedal is depressed. One APP sensor DTC will not cause the Reduced Engine Power message to be displayed. Two APP sensor DTCs for the same sensor also will not cause the Reduced Engine Power message to be displayed. However, if 2 or more DTCs are set involving more than one APP sensor, DTC P1125 will set.

This diagnostic procedure supports the following DTC

DTC P1125 Accelerator Pedal Position (APP) System

1. DTCs P0606, P2108 and U0107 are not set.
2. The ignition is ON.
3. The communications between the throttle actuator control (TAC) module and the powertrain control module (PCM) must be valid.

Two APP sensors are out of range or both APP sensors disagree with each other.

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.

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

1. 2: When the conditions that cause the APP sensor DTCs to set are corrected, the status of this DTC will change to History.

DTC P1125

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 did not switch enough times during a calibrated time period, DTC P1133 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 P1133 HO2S Insufficient Switching Bank 1 Sensor 1

The following conditions must be met for at least 2 seconds

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, P0453, P0454, P0455, P0464, P0496, P2135, P2A00 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 current misfire condition is not detected.
7. The ECT Sensor parameter is more than 65°C (149°F).
8. The Engine Run Time parameter is at least 60 seconds.
9. The evaporative emission (EVAP) purge solenoid is commanded ON.
10. The MAF sensor parameter is between 15-30 g/s.
11. The Engine Speed parameter is between 1,200-2,200 RPM.
12. The TP Sensor parameter is greater than 2 percent.
13. The Loop Status parameter is closed.
14. The vehicle is not in Park, Reverse or Neutral.

1. The PCM detects that the HO2S 1 voltage did not have enough switches from rich-to-lean and lean-to-rich during a 90 second monitoring period.
2. This diagnostic runs one 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 P1133

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 calculated transition time ratio is incorrect, DTC P1134 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 P1134 HO2S Transition Time Ratio Bank 1 Sensor 1

The following conditions must be met for at least one second

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, P0453, P0454, P0455, P0464, P0496, P2153, P2A00 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 current misfire condition is not detected.
7. The ECT Sensor parameter is more than 65°C (149°F).
8. The Engine Run Time parameter is at least 60 seconds.
9. The evaporative emission (EVAP) purge solenoid is commanded ON.
10. The MAF sensor parameter is between 15-30 g/s.
11. The Engine Speed parameter is between 1,200-2,200 RPM.
12. The TP Sensor parameter is at least 2 percent.
13. The Loop Status parameter is closed.
14. The vehicle is not in Park, Reverse or Neutral.

1. The PCM detects that the HO2S 1 voltage transition time ratio from rich-to-lean and lean-to-rich is incorrect during a 90 second monitoring period.
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 P1134

The ignition control module (ICM) controls spark timing when the engine is cranking. During this Bypass mode of operation, the ICM triggers each ignition coil in the proper sequence at a pre-calibrated timing advance. The ICM is connected directly to the powertrain control module (PCM) and includes the following circuits

1. The medium resolution engine speed signal
2. The camshaft position signal circuit
3. A low reference circuit
4. The low resolution engine speed signal circuit
5. The ignition control (IC) timing control circuit
6. The IC timing signal circuit

When the PCM begins receiving the 3X reference pulses from the ICM and the engine starts, the PCM applies 5 volts to the IC timing signal circuit. This allows the ICM to switch to the IC mode of operation and spark advance to be controlled by the PCM. The PCM monitors the IC timing signal circuit for errors. If the PCM detects a fault, DTC P1350 sets.

This diagnostic procedure supports the following DTC

DTC P1350 Ignition Bypass Circuit

1. The engine is running or cranking.
2. DTC P1350 runs continuously when the above condition is met.

The PCM detects a fault in the IC timing signal circuit for more than 9 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 number below refers to the step number on the diagnostic table.

1. 3: When the test lamp is tapped on the low resolution engine speed signal circuit, the PCM detects engine speed and applies 5 volts to the IC timing signal circuit.

DTC P1350

Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The catalytic converter must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm the catalytic converter. During a cold start, the engine idle speed is elevated and spark timing is retarded to allow the catalyst to warm quickly. This diagnostic monitors the following to build an exhaust energy model

1. Engine speed
2. Spark advance
3. Throttle position
4. Engine airflow
5. Engine coolant temperature
6. Engine runtime
7. Park/neutral position
8. Vehicle speed

The actual model is then compared to the expected exhaust energy model.

1. The engine is running and a cold start has been detected
2. Vehicle speed less than 2 km/h
3. Throttle position sensor less than 2 percent
4. Airflow per cylinder greater than 40 mg/cylinder
5. DTC P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0220, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0335, P0336, P0351, P0352, P0353, P0501, P0502, P0506, P0507, P0601, P0602, P0604, P0606, P0641, P0651, P1516, P1682, P2101, P2127, P2108, P2119, P2120, P2125, P2135, P2138, P2610 or U0107 are not set.

This DTC runs for 15 seconds within the first 2 minutes of start up. This diagnostic runs once per trip when a cold start has been determined.

The actual exhaust energy model does not match the expected exhaust energy model.

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/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.

Any loading of the engine that lowers engine RPM, such as with partial application of the clutch, etc. during the first 120 seconds of engine runtime may set this DTC.

Allow the engine to cool. Monitor the Cold Startup parameter, this should indicate Yes. Start and idle the engine for at least 2 minutes. DTC P1400 should run and pass.

1. Inspect the air intake system for the following: Modified, damaged or restricted Dirty or deteriorating air filter element Crankcase ventilation system for correct operation-refer to «Crankcase Ventilation System Inspection/Diagnosis»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l__crankcase-ventilation-system-inspectiondiagnosis) . Water intrusion Vacuum leak and other un-metered air downstream of the mass air flow (MAF) sensor Intake manifold leak
2. Inspect the exhaust system for the following: Water intrusion Exhaust leak Damaged, restricted, modified or enhanced exhaust system-Refer to «Symptoms - Engine Exhaust»(/buick/lacrosse/i-2004-2009/remont/exhaust/#engine-exhaust-system__symptoms-engine-exhaust) .
3. Inspect the engine mechanical for items that could alter the air flow into the combustion chamber-Refer to «Symptoms - Engine Mechanical»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) .

The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module is able to determine that the EGR valve is still open when the control module is commanding the EGR valve closed

1. The Ignition 1 Signal voltage parameter is more than 11 volts.
2. The EGR command will be disabled if the start-up engine coolant temperature (ECT) is less than 5°C (41°F) and will not enable until the ECT is more than 75°C (167°F).
3. The EGR valve is commanded to 0 percent for 20 seconds after the EGR valve has been commanded to open more than 40 percent for 0.5 second.
4. The EGR flow test is not running.

1. The EGR Position Sensor parameter is 0.23 volt more than the EGR Learned Minimum Position parameter when the Desired EGR Position parameter is commanded to 0 percent for 20 seconds.
2. The EGR Position Sensor parameter is more than 40 percent and is steady for 0.5 second after a test failure and before the next test will be run.
3. The above conditions are met 4 times.

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.

Inspect for excessive deposits on the EGR valve pintle or seat. Remove the EGR valve and inspect for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.

With the ignition ON and the engine OFF, command the EGR from 0-100 percent. The EGR Position Sensor parameter should remain within 3 percent of the Desired EGR Position parameter.

1. With the ignition ON and the engine OFF, observe the DTC information on the scan tool. If DTC P0641 is also set, diagnose those DTCs first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) .
2. Start the engine and observe the EGR Position parameter. The EGR Position parameter should be less than 1 percent.
3. Disconnect the EGR harness connector and observe the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 0 percent. If the EGR Position Sensor parameter is more than 0 percent test the EGR Position Sensor signal circuit for a short to voltage or a faulty control module.
4. Command the EGR valve from 0 percent to 100 percent with a scan tool and observe the EGR Position Variance parameter. The EGR Position Variance parameter should be less than 15 percent. If the EGR Position Variance parameter is more than 15 percent test the EGR 5-volt reference circuit and the EGR Low Reference circuit for an open or high resistance or a faulty control module.
5. Using a 3-amp fused jumper wire jumper the EGR 5-volt reference circuit to the EGR Position Sensor Signal circuit at the EGR harness connector and monitor the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 99 percent. If the EGR Position Sensor parameter is less than 99 percent test for an open, high resistance or a short to ground in the EGR Pintle Position Signal circuit.
6. Disconnect the control module and measure the resistance of the EGR High Control circuit and the EGR Low Control circuit. There should be less than 3 ohms of resistance on each circuit. If the resistance is more than 3 ohms, test each circuit for high resistance.

1. If all circuits test OK, replace the EGR valve.

1. «Engine Control Module Programming and Setup»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#programming-and-setup-all-systems__engine-control-module-programming-and-setup) for control module replacement and programming
2. «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2)

The commanded throttle position (TP), based on accelerator pedal position (APP), is compared to the actual throttle position. The TP values should be within a calibrated range of each other. The throttle actuator control (TAC) module monitors the commanded and actual throttle position. If the TAC module detects that the commanded and actual throttle positions are not within a calibrated range of each other or the TAC module or the powertrain control module (PCM) cannot determine throttle position or if both TP sensors are invalid, a message is sent to the PCM across serial data and DTC P1516 is set.

This diagnostic procedure supports the following DTC

DTC P1516 Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

1. The ignition is in the crank or run position.
2. The system is not in battery saver mode.
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 TAC module detects that the commanded and the actual throttle positions are not within a calibrated range of each other. OR
2. The TAC module or the PCM cannot determine throttle position. OR
3. Both TP sensors are invalid.

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. Inspect for mechanical conditions or for binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.
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) .

1. 3: Both TP sensor DTCs active at the same time will result in DTC P1516 also set. It is necessary to diagnose both sensor faults individually.
2. 4: A DTC U0107 set along with a sensor DTC may indicate a sensor fault. Refer to «DTC P2135»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-dtc-p2125-to-dtc-u0107) .

DTC P1516

The output driver module (ODM) is a control chip inside of the powertrain control module (PCM). The PCM contains multiple ODMs. ODMs provide grounded output control of devices. Each ODM output has an internal feedback circuit that connects to the PCM microprocessor. The PCM monitors voltage through the ignition 1 voltage circuit. Excessive voltage or current may cause damage to the PCM.

1. The ignition is ON.
2. The system voltage is between 9-11 volts.

1. The PCM has detected a voltage greater than 26.5 volts.
2. Excessive current is detected on any circuit to the ODM.
3. The above conditions are present 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. 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.

A condition with the charging system may cause this DTC to set. Refer to CHARGING SYSTEM TEST .

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)

1. «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-data-list)
2. «Scan Tool Output Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-1-of-2__scan-tool-output-controls)

With the ignition ON, the Observe the Output Driver Status with a scantool. All parameters should indicate OK or no fault present

1. Observe the scantool for any other DTCs. If DTC P0560 is also set, refer to DTC P0560 to repair the charging system.
2. Observe the Observe the Output Driver Status with a scantool. If any parameter does NOT indicate OK, test for a short to voltage on the control circuit of the component that indicated a fault.

1. If all circuits test OK replace the PCM.

Control Module References for PCM replacement, programming and setup

Repair Verification

The commanded throttle position (TP), based on accelerator pedal position (APP), is compared to the actual throttle position. The TP values should be within a calibrated range of each other. The throttle actuator control (TAC) module monitors the commanded and actual throttle position. If the TAC module detects that the commanded and actual throttle positions are not within a calibrated range of each other, a message is sent to the powertrain control module (PCM) across serial data and DTC P2101 is set.

This diagnostic procedure supports the following DTC

DTC P2101 Control Module Throttle Actuator Position Performance

1. The ignition is in the crank or run position.
2. The system is not in Battery Saver mode.
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 TAC module detects that the commanded and actual throttle positions are not within a calibrated range of each other. OR
2. The TAC module or the PCM cannot determine 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.

1. Inspect for mechanical conditions or for binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.
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 P2101

The throttle actuator control (TAC) module contains data, which is essential for proper TAC system operation. The TAC module continuously checks the integrity of this data. If the TAC module detects a fault with electrically erasable programmable read only memory (EEPROM) or the TAC module detects a low voltage while the voltage on the powertrain control module (PCM) is not low or the TAC module detects the vehicle ID from TAC module does not agree with the vehicle ID from the PCM, DTC P2107 sets.

This diagnostic procedure supports the following DTC

DTC P2107 Throttle Actuator Control (TAC) Module Internal Circuit

1. DTCs P0606, P2108 and U0107 are not set.
2. The ignition is in the crank or run position.

If the TAC module detects low voltage, a fault with the EEPROM or vehicle ID recorded in the TAC module does not match the vehicle ID recorded in the PCM.

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.

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

DTC P2107

The throttle actuator control (TAC) module contains data, which is essential for proper TAC system operation. The TAC module continuously checks the integrity of this data. If the TAC module is unable to write or read data to and from random access memory (RAM) or the TAC module is unable to correctly read data from the flash memory or an internal TAC module processor fault is detected, DTC P2108 sets.

This diagnostic procedure supports the following DTC

DTC P2108 Throttle Actuator Control (TAC) Module Performance

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 powertrain control module (PCM) must be valid.

The TAC module determines that an internal data test did not pass.

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 P2108

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 throttle position. The throttle blade is spring loaded in both directions and at rest is slightly open. When throttle blade is not driven in either direction it returns to this position. If the TAC module determines that the throttle blade has not returned to the correct de-energized position, the TAC module sends a message to the powertrain control module (PCM) across serial data and DTC P2119 sets.

This diagnostic procedure supports the following DTC

DTC P2119 Throttle Closed Position Performance

1. DTC U0107 is not set.
2. The ignition is ON and the engine is OFF.
3. The ignition voltage is more than 8.5 volts.
4. The system is not in Battery Saver mode.

The TAC module detects that the throttle blade has not returned to the correct de-energized position.

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.

Inspect for mechanical conditions or for binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.

DTC P2119

The accelerator pedal position (APP) sensor 1 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 1 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 1 signal or the APP sensor 5-volt reference voltage is outside the predetermined range, DTC P2120 sets.

This diagnostic procedure supports the following DTC

DTC P2120 Accelerator Pedal Position (APP) Sensor 1 Circuit

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

1. The APP sensor 1 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.

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 P2120

See also:
• Evaporative Emissions (EVAP) Hose Routing Diagram
• Diagnostic System Check - Vehicle
• Special Tools
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Circuit Testing
• Wiring Repairs
• Diagnostic Trouble Code (DTC) List - Vehicle
• Engine Controls Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Control Module References
• Testing for a Short to Voltage
• Testing for Continuity
• Lifting and Jacking the Vehicle
• Diagnostic Repair Verification
• Scan Tool Data List
• Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
• Manifold Absolute Pressure (MAP) Sensor Replacement
• Scan Tool Output Controls
• Battery Inspection/Test
• Engine Cranks but Does Not Run
• Silicon Contamination of Heated Oxygen Sensors Notice
• Heated Oxygen and Oxygen Sensor Notice
• Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice
• Probing Electrical Connectors
• Crankcase Ventilation System Inspection/Diagnosis
• Symptoms - Engine Exhaust
• Symptoms - Engine Mechanical
• Engine Control Module Programming and Setup
• DTC P2135
• CHARGING SYSTEM TEST