Engine Control System - 3.8l - Troubleshooting Buick LaCrosse I

Important Preliminary Inspections Before Starting

Before using the Symptom tables, perform the following

1. Perform «Diagnostic System Check - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information) and verify all of the following items: Ensure that the engine control module and malfunction indicator lamp (MIL) are operating correctly. Ensure that there are no diagnostic trouble codes (DTCs) that are stored. Scan tool data is within a normal operating range. Refer to «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. Verify the customer concern.
3. Perform the Visual/Physical Inspection in this section. The visual/physical inspection is extremely important and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition.
4. Locate the correct symptom. Perform the tests and inspections associated with the symptom.

Identifying Intermittent Conditions

Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition

1. Moisture, water intrusion in connectors, terminals and components
2. Connector mating
3. Terminal contact
4. High circuit or component resistance - High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
5. Harness that is located too tight or chaffed circuits
6. High or low ambient temperature
7. High or low engine coolant temperatures
8. High underhood temperatures
9. Heat build up in component or circuit due to circuit resistance, poor terminal contact or high electrical load
10. High or low system voltage
11. High vehicle load conditions
12. Rough road surface
13. Electro-magnetic Interference (EMI)/circuit interference from relays, solenoids or other electrical surge
14. Incorrect installation of non-factory, aftermarket and after factory add on accessories

If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions.

Visual/Physical Check

Note. Use the connector test adapter kit J 35616-A for any test that requires probing the following items: The PCM harness connectors The electrical center fuse/relay cavities The component terminals The component harness connector Using this kit will prevent damage caused by the improper probing of connector terminals.

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save time. This inspection should include the following areas

1. Ensure that the control module grounds are clean, tight and correctly located. Refer to «Master Electrical Component List»(/buick/lacrosse/i-2004-2009/remont/electrical-component-locations/#wiring-systems-component-views__master-electrical-component-list) and «Power and Grounding Connector End Views»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#wiring-systems-power-and-ground-inline-harness-and-splice-pack-connector-end-views__power-and-grounding-connector-end-views) .
2. Inspect vacuum hoses for splits, kinks and proper connections, as shown on the Vehicle Emission Control Information label. Inspect thoroughly for any type of a leak or a restriction. Refer to «Emission Hose Routing Diagram (L26, NU3)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) and «Evaporative Emissions (EVAP) Hose Routing Diagram»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Inspect for a dirty or restricted air filter.
4. Inspect for water intrusion in the mass air flow/intake air temperature (MAF/IAT) sensor connector, heated oxygen sensor (HO2S) connectors, control module connectors or any other harness connectors.
5. Inspect the air intake ducts, particularly between the MAF sensor and the throttle body for the following conditions: Collapsed Damaged areas Looseness Incorrect installation Leaking
6. Inspect for air leaks at the throttle body mounting area, the mass air flow (MAF) sensor and intake manifold sealing surfaces.
7. Inspect the wiring harness for the following conditions: poor connections pinches cuts
8. Inspect for loose, damaged, unseated or missing sensors/components.
9. Inspect terminals for corrosion and correct contact.

Symptoms

Use the following symptoms in order to isolate possible systems that are associated with the condition

Symptoms

Symptoms - Fuel System

Fuel System

Symptoms - Ignition System

Ignition System

Symptoms - Sensors/Systems

Sensor/System

Diagnostic Fault Information

Circuit/System Description

Ignition voltage is supplied to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit.

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

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

The MIL should turn ON and OFF when commanded with a scan tool.

Circuit/System Testing

1. Turn OFF the ignition.
2. Disconnect the 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 instrument panel cluster (IPC). If the MIL control circuit tested OK and the MIL went out when the ECM was disconnected, replace the ECM.
4. Measure for 12 volts from the MIL ignition voltage circuit in the ECM 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 1 volt from the MIL control circuit in the ECM harness connector to ground. If there is more than 1 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 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.

Repair Procedures

1. Control Module References for ECM replacement, setup and programming
2. «Instrument Panel Cluster (IPC) Replacement»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console)

This Engine Cranks but Does Not Run is an organized approach to identify a condition which causes the engine to crank but not start. This diagnostic directs the technician to the appropriate system diagnosis.

This diagnostic assumes the system voltage levels are adequate for starter motor operation. Refer to Battery Inspection/Test and Engine Cranks Slowly . Fuel level and fuel quality should be determined for correct diagnosis.

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)

Attempt to start the engine. Engine should start and run.

1. Crank the engine for up to 30 seconds.
2. Observe the Engine DTC information with a scan tool. If any of the following DTCs are set 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) : P0201-P0206, P0335, P0336, P0351-P0353, P0601, p0602, P0604, P0685, P1516, P2610
3. Observe the engine speed parameter while cranking the engine. If engine RPM is not indicated, refer to «Electronic Ignition (EI) System Diagnosis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
4. Install a spark tester.
5. Crank the engine for 15 seconds. Spark should be observed from the Spark Tester. If spark is not observed refer to «Crankshaft Position Sensor (CKP) System Diagnosis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
6. With the ignition ON and the engine OFF, test the fuses that are supplied by the powertrain relay for voltage. The test lamp should illuminate at each test point for the following fuses: Emission Fuse Ignition 1 Fuse If the testlamp does not illuminate on at least one side of each fuse refer to «DTC P0685»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-dtc-p0451-to-dtc-p2120) .
7. Command the fuel pump ON and OFF. Fuel pump should energize when commanded ON and De-energize when commanded OFF If the fuel pump does not respond refer to «Fuel Pump Electrical Circuit Diagnosis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
8. Turn OFF the ignition.
9. Install the J 34730-1A Fuel Pressure Gage. Turn ON the ignition and command the fuel pump ON while observing the J 34730-1A . The fuel pressure should be between 384-425 kPa (56-62 psi). If the fuel pressure is not within 384-425 kPa (56-62 psi) refer to «Fuel System Diagnosis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
10. Inspect for the following conditions: Compare the actual engine coolant temperature to the ECT parameter. Air filter and air intake system for restrictions and obstructions Test the fuel for contamination. Refer to «Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) . Inspect the spark plug and spark plug wires. Refer to «Spark Plug Wire Inspection»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__spark-plug-wire-inspection) and «Spark Plug Inspection»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__spark-plug-inspection) . Test the exhaust system for restrictions. Refer to «Restricted Exhaust»(/buick/lacrosse/i-2004-2009/remont/exhaust/#engine-exhaust-system) .

Circuit Description

When you turn ON the ignition switch, the control module energizes the fuel pump relay which powers the fuel pump ON. The pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

Diagnostic Aids

The following conditions may have caused the fuel pump fuse to open

1. The fuse is faulty.
2. There is an intermittent short to ground in the fuel pump battery voltage circuit.
3. The fuel pump has an intermittent internal condition.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

1. 2: Command both the ON and OFF states. Repeat the commands as necessary.
2. 3: This step determines if the condition is located on the coil side or the switch side of the fuel pump relay.
3. 4: This step verifies that the powertrain control module (PCM) is providing voltage to the control circuit of the fuel pump relay.
4. 5: This step tests for an open in the ground circuit to the fuel pump relay.
5. 6: This step determines if a voltage is constantly being applied to the control circuit of the fuel pump relay.
6. 13: This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.
7. 15: Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.
8. 17: Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.

Fuel Pump Electrical Circuit Diagnosis

When you turn ON the ignition switch, the control module enables the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through the fuel feed pipe to the fuel injection system. The fuel pump is an electric pump that is attached to the fuel sender assembly, which is mounted in the fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. The fuel pressure regulator, located in the fuel tank, is attached to the fuel sender assembly. The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure.

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

1. 2: This step verifies that the fuel pump is operating.
2. 4: This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
3. 7: This step isolates the condition. Replace the fuel sender assembly, if the fuel pressure remains constant, after closing the valve on the fuel pipe shut-off adapter. Locate and replace the leaking fuel injector if the pressure continues to decrease after closing the valve on the adapter.
4. 10: This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.

Fuel System Diagnosis

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied directly to the fuel injectors through the powertrain power distribution relay and a fuel injector mini fuse. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver.

1. A fuel injector control circuit DTC may not set, but a misfire may be apparent. Monitoring the misfire current counters or misfire graph, may help isolate the fuel injector that is causing the condition.
2. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings increases as the temperature of the fuel injector increases. Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
3. A fuel injector coil winding resistance that is too high or too low will affect engine driveability. Perform the fuel injector coil test within the conditions of the customers concern. A fuel injector condition may only be apparent at a certain temperature or under certain conditions.
4. If the fuel injector coil test does not isolate the condition perform the fuel injector balance test. Refer to «Fuel Injector Balance Test with Special Tool»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) or «Fuel Injector Balance Test with Tech 2»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .

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

1. 3: This step tests each fuel injector resistance within a specific temperature range. If any of the fuel injectors display a resistance outside of the specified value, replace the fuel injector.
2. 4: This step determines if all of the fuel injectors are within 3 ohms of each other. If the highest resistance value is within 3 ohms of the lowest resistance value, then all of the fuel injector coil windings are OK.
3. 5: This step determines which fuel injector is faulty. After subtracting the highest and lowest resistance values from the average value, replace the fuel injector that has the greatest resistance difference from the average.

Fuel Injector Coil Test

Scheme 120

System Description

The scan tool is first used to energize the fuel pump relay. The fuel injector tester is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.

Fuel Injector Balance Test Example (Actual Results May Vary)

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

1. 3: The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 6: If the pressure drop value for each fuel injector is within 20 kPa (3 psi) of the average pressure drop value, the fuel injectors are flowing properly.

Fuel Injector Balance Test with Special Tool

The scan tool first energizes the fuel pump and then the injectors for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.

Fuel Injector Balance Test Example (Actual Results May Vary)

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

1. 3: The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 4: This step tests the ability of the fuel system to produce pressure within a specified range necessary for the correct engine performance.
3. 5: This step tests the ability of the fuel system to maintain fuel pressure after the pump stops.
4. 6: If the pressure drop value for each fuel injector is within 20 kPa (3 psi) of the average pressure drop value, the fuel injectors are flowing properly.

Fuel Injector Balance Test with Tech 2

Fuel quality can affect vehicle performance. Gasoline and gasoline blends that are contaminated or contain excessive amounts of alcohol can affect vehicle driveability, fuel economy, fuel system components and emissions. Excessive alcohol in the fuel may cause fuel system corrosion, deterioration of rubber components and subsequent fuel filter restriction. Some types of alcohol are more detrimental to fuel system components than others. Ethanol is commonly used in gasoline, but in concentrations of no more than 10 percent. Some fuels, such as E85, contain a very high percentage of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions in vehicles such as hesitation, lack of power, stalling or no start. If excessive alcohol in the fuel is suspected, then use the following procedure to test the fuel quality.

Test Procedure

1. Turn ON the J 44175 Fuel Composition Tester.
2. Verify the fuel composition tester is operational by measuring the AC frequency output with a DMM. Refer to «Measuring Frequency»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__measuring-frequency) in Wiring Systems. A frequency without a fuel sample in the test cell indicates that the tester is working correctly.
3. Install the fuel pressure gage. Refer to «Fuel Pressure Gage Installation and Removal»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
4. Close the bleed valve on the fuel pressure gage.
5. Place the bleed hose (1) of the fuel pressure gage into the 100 ml beaker (2).
6. Command the fuel pump ON with a scan tool.
7. Slowly open the bleed valve on the fuel pressure gage until an adequate fuel sample is obtained.
8. If water appears in the fuel sample, replace the fuel in the vehicle. Refer to «Fuel System Cleaning»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-system-cleaning) .
9. Pour the fuel sample from the beaker (1) into the J 44175 until the level of the fuel is at the top of each fuel test port (2).
10. Observe the diagnostic LEDs on the fuel composition tester. If the red fuel diagnostic LED is illuminated, a fuel contamination condition exists. Refer to «Fuel System Cleaning»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-system-cleaning) .
11. Measure the output frequency of the fuel composition tester.
12. Subtract 50 from the reading on the DMM to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the following table.
13. If the fuel sample contains more than 10 percent ethanol, replace the fuel in the vehicle.

Fuel Composition Test Examples

Manifold Absolute Pressure (MAP) Sensor Diagnosis

Typical Scan Tool Data

MAP Sensor

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

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

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

Poor idle characteristics may be due to uncontrolled fueling caused by an open or high resistance in the heated oxygen sensor (HO2S) 1 low signal circuit. Before replacing any component, ensure that this condition does not exist.

Special Tools Required

J 23738-A Mityvac

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)

Scan Tool Data List

Always perform the Diagnostic System Check - Vehicle .

1. Start the engine.
2. Monitor the DTC information with the scan tool.
3. If DTC P0641or P0651 is also set then correct DTC P0641or P0651 first.
4. Inspect for the following conditions: Disconnected, damaged or incorrectly routed vacuum hoses MAP sensor disconnected from the vacuum source Restrictions in the MAP sensor vacuum source Intake manifold vacuum leaks Check for a properly functioning oxygen sensor.
5. Turn OFF the ignition.
6. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
7. Connect a J 23738-A to the MAP sensor.
8. Turn ON the ignition, with the engine OFF.
9. Observe the MAP sensor pressure with the scan tool.
10. Apply vacuum to the MAP sensor with the J 23738-A in 1 inch Hg increments until 15 inches Hg is reached. Each 1 inch Hg should decrease MAP sensor pressure by 3-4 kPa. Monitor the MAP sensor pressure to see if the decrease in pressure in consistent. If decrease in pressure is not consistent then, test for intermittent and poor connections at the MAP sensor.
11. Apply vacuum with the J 23738-A until 20 inches Hg is reached. Observe the MAP sensor pressure for less than 34 kPa. If more than 34 kPa, test for an intermittent and for a poor connection at the MAP sensor.
12. With the ignition ON and the engine OFF.
13. Disconnect the MAP sensor.
14. Measure for 4.8-5.2 volts from the 5-volt reference circuit of the MAP sensor to a good ground, with a DMM. If more than specified value than test the circuit for a short to voltage or faulty control module. If less than specified value than test the circuit for high resistance, an open or an intermittent and poor connection or at the control module or a faulty control module.
15. Disconnect the MAP sensor
16. Use a scan tool and observe the MAP sensor for less than 12 kPa. If the MAP sensor is more than 12 kPa then test the MAP sensor signal circuit for a short to voltage or a faulty control module.
17. Use a 3-amp fused jumper wire and connect it between the MAP sensor 5-volt reference circuit and the MAP sensor signal circuit.
18. Use a scan tool and observe the MAP sensor for more than 103 kPa. If the MAP sensor is less than 103 kPa then test the MAP sensor signal circuit for high resistance or a faulty control module.
19. With the 3-amp fused jumper wire still connected between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor. Observe the MAP sensor parameter with the scan tool for 4.9 volts. If more than 4.9 volts then replace the MAP sensor. If less than 4.9 volts then, test the MAP sensor signal circuit between the control module and the MAP sensor for a short to ground, an open or high resistance. Test for an intermittent and for a poor connection at the control module, if tests OK then replace the control module.
20. Turn OFF the ignition and allow the control module to power down.
21. With a DMM measure for less than 5 ohms of resistance between the low reference circuit of the MAP sensor and a good ground. If the resistance is more than 5 ohms, then test the circuit for a high resistance or a faulty control module.
22. If the MAP sensor circuits test normal, then replace the MAP sensor.

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

Repair Verification

Diagnostic Repair Verification

The ignition control module (ICM) has independent power and ground circuits. The circuits between the ICM and the powertrain control module (PCM) consists of the following circuits

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

For a complete system description, refer to Electronic Ignition (EI) System Description .

Electronic Ignition (EI) System Diagnosis

The ignition control module (ICM) monitors the crankshaft position (CKP) sensor sync signal when the engine is cranking. The CKP sync signal is passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The CKP sync signal is used to determine the correct cylinder pair and initiate the ignition coil firing sequence. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 signal circuit. The 18X reference pulses are used for fuel injection and ignition control. After the ICM receives both signals, the ICM passes the 18X and 3X reference signals to the powertrain control module (PCM). The camshaft position sensor and the CKP sensor share a 12-volt reference and a low reference circuit. The CKP sensor consists of the following circuits

1. A 12-volt reference circuit
2. A low reference circuit
3. A CKP sensor 1 signal circuit
4. A CKP sensor 2 signal circuit

Crankshaft Position Sensor (CKP) System Diagnosis

Description

Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the inspection/maintenance (I/M) emission inspection in order to renew license plates. This is accomplished by viewing the I/M System Status display on a scan tool. Using a scan tool, the technician can observe the I/M System Status in order to verify that the vehicle meets the criteria that comply with the local area requirements.

Conditions for Updating the I/M System Status

Each system monitor requires at least one and sometimes several diagnostic tests. The result of each test is reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs composing the monitor have Run and Passed or when any one of the DTCs comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the system monitor is complete, the I/M System Status display will indicate YES in the Completed column.

For example, when the HO2S Heater Status indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has four heated oxygen sensors, either all four heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

1. The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
2. The battery has been disconnected or discharged below operating voltage.
3. The control module power or ground has been interrupted.
4. The control module has been reprogrammed.
5. The control module DTCs have been cleared.

Monitored Emission Control Systems

The OBD II System monitors all emission control systems that are on-board. The OBD II regulations require monitoring of the following

1. The air conditioning system
2. The catalytic converter efficiency
3. Comprehensive component monitoring-Emission related inputs and outputs
4. The evaporative emission (EVAP) system
5. The fuel delivery system
6. Heated catalyst monitoring
7. Misfire monitoring
8. The oxygen sensor system (O2S or HO2S)
9. The oxygen sensor heater system (HO2S heater)

For the specific DTCs required for each system, refer to. Systems such as fuel delivery, misfire and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.

Review the I/M System Status indicators. All I/M System Status indicators should report YES.

1. Observe the Engine DTC information with a scan tool. If a DTC is set that would prevent the I/M System Status tests from completing, diagnose that DTC before continuing. Refer to «Inspection/Maintenance (I/M) System DTC Table»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting__inspectionmaintenance-im-system-dtc-table) .
2. Review applicable service bulletins for software updates that would prevent the I/M System Status tests from completing. If a control module re-program or other repair is required, perform the «Inspection/Maintenance (I/M) Complete System Set Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .
3. Observe the I/M System Status indicators. If any I/M System Status indicators report NO, perform the «Inspection/Maintenance (I/M) Complete System Set Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting) .

The purpose of the Inspection/Maintenance (I/M) complete system set procedure is to satisfy the enable criteria necessary to execute all of the I/M readiness diagnostics and complete the trips for those particular diagnostics. When all I/M monitored diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform the Inspection/Maintenance (I/M) Complete System Set Procedure if any I/M System Status indicators are set to NO.

Conditions for Meeting a Cold Start

1. The ignition voltage between 11.0 and 18.0 volts
2. The barometric pressure (BARO) is more than 75 kPa
3. The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F)
4. The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
5. The difference between the IAT and the ECT is 6°C (10.8°F)
6. The ambient air temperature is between 4-30°C (39-86°F)
7. Fuel level is between 15 and 85 percent
8. Vehicle has NOT been refueled since the last cold start ignition cycle

Review the Inspection/Maintenance (I/M) System Status indicators. All I/M System Status indicators should report YES.

Inspection/Maintenance (I/M) System Set Procedure

1. Ensure that the vehicle meets the conditions for a cold start listed above. If the EVAP I/M System Status indicator displays NO, perform the EVAP Service bay test if applicable. If the EVAP Service bay test is NOT available, it may take up to 6 drive cycles, with 17 hours between drive cycles for the EVAP I/M System Status Indicator to transition to YES. The EVAP I/M System Status indicator requires several drive and 17 hour key OFF cycles to complete before the indicator will transition. If the O2S Heater System Status indicator displays NO, ensure that the ignition has been turned OFF for at least 10 hours.
2. Turn OFF all accessories; HVAC system, other electrical loads, including aftermarket/add-on equipment, etc. and open the hood.
3. Set the vehicle parking brake and ensure the vehicle is in park for automatic transmission or neutral for manual transmission.
4. Turn the ignition ON with the engine OFF for 1 minute.
5. Start and idle the engine for 2 minutes and until 65°C (149°F) is achieved.
6. Run the engine for 6.5 minutes within the following conditions: MAF parameter between 4-30 g/s Engine speed steady between 1000-3000 RPM
7. Return the engine to idle for 1 minute.
8. Apply and hold brake pedal and shift to Drive for automatic or apply clutch pedal for manual and operate the vehicle within the following conditions for 2 minutes: Depress the accelerator pedal until TP Sensor angle is more than 2 percent. MAF signal between 15-30 g/s RPM steady between 1200-2000 RPM
9. Release the accelerator pedal and shift the vehicle to Park for automatic or Neutral and release clutch pedal for manual and allow the engine to idle for 2 minutes.
10. Quickly depress the accelerator pedal until TP Sensor Angle is more than 8 percent and return to idle, repeat 3 times.
11. Allow engine to idle for at least 2 minutes.
12. Close the hood, release the parking brake and drive vehicle at 24 km/h (15 mph) or slower for 2 minutes.
13. Continue to drive the vehicle for at least 5.5 miles between 45-112 km/h (28-70 mph) with the vehicle reaching at least 80 km/h (50 mph).
14. Release the accelerator pedal for at least 3 seconds. This will allow the vehicle to enter the decel fuel cut off. Repeat 4 more times.
15. Depress the accelerator pedal until the TP Sensor angle is between 3-20 percent and maintain for 1 minute.
16. Safely stop the vehicle, with the engine in drive for automatic or neutral with the clutch pedal depressed and parking brake applied for manual. Allow the vehicle to idle for 2 minutes.
17. Shift the vehicle to park for automatic and neutral for manual. Turn OFF the ignition and exit the vehicle. Do NOT disturb the vehicle for 45 minutes.
18. Observe the Inspection/Maintenance (I/M) System Status with a scan tool. All of the I/M System Status indicators should display YES. If the EVAP I/M System Status indicator displays NO turn OFF the ignition for 17 hours, ensure that the vehicle meets the conditions for a cold start and repeat steps 13-18 three more times or until the EVAP I/M System Status indicator transitions to YES. If the indicator continues to display NO, refer to the «Inspection/Maintenance (I/M) System DTC Table»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting__inspectionmaintenance-im-system-dtc-table) to identify the DTCs that did not run.

1. If any of the I/M System Status indicators display NO, refer to the «Inspection/Maintenance (I/M) System DTC Table»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-troubleshooting__inspectionmaintenance-im-system-dtc-table) for the indicator which did not display YES. The I/M System DTC Table identifies the DTCs associated with each I/M System Status Indicator.

Inspection/Maintenance (I/M) System DTC Table

Inspection/Maintenance (I/M) System DTC Table

See also:
• Diagnostic System Check - Vehicle
• Scan Tool Data List
• Testing for Intermittent Conditions and Poor Connections
• Master Electrical Component List
• Power and Grounding Connector End Views
• Emission Hose Routing Diagram (L26, NU3)
• Symptoms - Engine Exhaust
• Symptoms - Engine Mechanical
• Symptoms - Engine Cooling
• Charging System Test
• Restricted Exhaust
• Air Conditioning (A/C) System Performance Test (L26)
• Symptoms - HVAC Systems - Manual
• Symptoms - HVAC Systems - Automatic
• ABS Description and Operation
• Symptoms - Antilock Brake System
• Crankcase Ventilation System Inspection/Diagnosis
• Brakes Drag
• DTC P0442
• Spark Plug Wire Inspection
• Ignition System Specifications
• Temperature vs Resistance
• Electronic Ignition (EI) System Description
• Powertrain Control Module (PCM) Connector End Views
• Engine Controls Connector End Views
• Circuit Testing
• Connector Repairs
• Wiring Repairs
• Scan Tool Output Controls
• Diagnostic Repair Verification
• Instrument Panel Cluster (IPC) Replacement
• Battery Inspection/Test
• Engine Cranks Slowly
• Diagnostic Trouble Code (DTC) List - Vehicle
• DTC P0685
• Spark Plug Inspection
• Control Module References
• Fuel Pressure Relief Procedure
• Testing for Continuity
• Special Tools
• Measuring Frequency
• Fuel System Cleaning
• Manifold Absolute Pressure (MAP) Sensor Replacement
• Using Connector Test Adapters
• DTC P0140
• DTC P2A01
• Symptoms - Fuel System
• Symptoms - Ignition System
• Symptoms - Sensors/Systems
• Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool)
• Inspection/Maintenance (I/M) System DTC Table