Engine Control System - 3.6l (ly7) - Troubleshooting Buick LaCrosse I

Important Preliminary Inspections Before Starting

Before using this article perform the Diagnostic System Check - Vehicle in Vehicle DTC Information and verify all of the following conditions

1. The engine control module (ECM) and the malfunction indicator lamp (MIL) are operating correctly.
2. There are no diagnostic trouble codes (DTCs) stored.
3. The scan tool data is within the normal operating range. Refer to «Scan Tool Data List»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-1-of-2__scan-tool-data-list) .
4. Verify the customer concern and locate the correct symptom. Inspect the items indicated under that symptom.
5. Several of the symptom procedures ask for a careful visual/physical inspection. This step is extremely important and can lead to correcting a condition without further inspections and can save valuable time.
6. If an intermittent condition exists as a start and then a stall, inspect for any DTCs related to the theft deterrent system. 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) in Vehicle DTC Information.
7. Verify the proper installation of any of the following non-original equipment accessories: Lights Cellular phone Remote starter system Non-factory installed alarm

1. Use the following tables when diagnosing a symptom concern: «Hard Start»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__hard-start) «Surges/Chuggles»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__surgeschuggles) «Lack of Power, Sluggishness or Sponginess»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__lack-of-power-sluggishness-or-sponginess) «Detonation/Spark Knock»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__detonationspark-knock) «Hesitation, Sag, Stumble»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__hesitation-sag-stumble) «Cuts Out, Misses»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__cuts-out-misses) «Poor Fuel Economy»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__poor-fuel-economy) «Poor Fuel Fill Quality»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__poor-fuel-fill-quality) «Rough, Unstable or Incorrect Idle and Stalling»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__rough-unstable-or-incorrect-idle-and) «Dieseling, Run-On»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__dieseling-run-on) «Backfire»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__backfire)
2. If the condition cannot be isolated using the appropriate table, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) for further diagnosis.

Intermittent Conditions

Intermittent Conditions

Hard Start

Hard Start

Surges/Chuggles

Surges/Chuggles

Lack of Power, Sluggishness or Sponginess

Lack of Power, Sluggishness or Sponginess

Detonation/Spark Knock

Detonation/Spark Knock

Hesitation, Sag, Stumble

Hesitation, Sag, Stumble

Cuts Out, Misses

Cuts Out, Misses

Poor Fuel Economy

Poor Fuel Economy

Poor Fuel Fill Quality

Poor Fuel Fill Quality

Rough, Unstable or Incorrect Idle and Stalling

Rough, Unstable or Incorrect Idle and Stalling

Dieseling, Run-On

Dieseling, Run-On

Backfire

Backfire

Description

The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.

The Engine Cranks but Does Not Run diagnostic table assumes the following

1. The battery is completely charged. Refer to «Battery Inspection/Test»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) .
2. The engine cranking speed is within specifications. Refer to «Engine Cranks Slowly»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) .
3. There is adequate fuel in the fuel tank.

Diagnostic Aids

1. The engine control module (ECM) uses the camshaft position (CMP) sensors to determine engine speed and position when there is a crankshaft position (CKP) sensor condition.
2. The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a CKP sensor condition in the signal circuit, the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the CMP sensors. During a limp home mode, the following additional DTCs may set and should be ignored: DTC P0324 Knock Sensor (KS) Module Performance DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1
3. Refer to «Symptoms - Engine Controls»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) and «Hard Start»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__hard-start) for further diagnosis.

Test Description

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

1. 2: This step determines if there is a condition with the main relay causing the no start condition. Use the Capture Info function to store any DTC information that may have set previously, before clearing the DTC information.
2. 3: This step determines if there is an internal ECM condition or sub-system component DTC causing the no start.
3. 5: This step determines if the fuel pump is turning ON. An audible sound can be heard at the fuel injector rail when the fuel pump is turned ON.

Engine Cranks but Does Not Run

Circuit Description

When the ignition switch is turned ON, the control module enables the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain on as long as the engine is running or cranking and the control module is receiving reference pulses. If no reference pulses are present, the control module de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped.

Listen for an audible hiss from the fuel pump when the fuel pump relay is commanded ON. A vibration in the fuel feed line when the fuel pump relay is commanded ON indicates that the fuel pump is operating.

For an intermittent condition, refer to Intermittent Conditions .

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 circuit.
3. 7: This step tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.
4. 9: This step verifies that the fuel pump fuse is providing voltage to the fuel pump relay.
5. 10: This step jumps the fuel pump relay in order to activate the fuel pump.
6. 15: 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.

Fuel Pump Electrical Circuit Diagnostic

System Description

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The fuel system is a returnless on-demand design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

The fuel tank stores the fuel supply. An electric turbine style fuel pump attaches to the fuel sender assembly inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter, contained in the fuel sender assembly and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel sender assembly. The function of the venturi pump is to fill the fuel sender assembly reservoir. The fuel pressure regulator, a part of the fuel sender assembly, maintains the correct fuel pressure to the fuel injection system. The fuel pump and sender assembly contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cracking times.

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 primary fuel tank module 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 engine control module (ECM) enables the appropriate fuel injector on the intake stroke for each cylinder. A voltage is supplied directly to the fuel injectors. The ECM controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or low, will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

1. Monitoring the misfire current counters or misfire graph, may help isolate the fuel injector that is causing the condition.
2. Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
3. 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-36l-ly7-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 121

Fuel Injector Balance Test Example (Typical)

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

1. 3: The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 5: This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated. The fuel pressure should reach a steady value.
3. 6: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. (Scheme 121)

Fuel Injector Balance Test Procedure

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.

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

1. 3: The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 4: The fuel pressure should be within the specified range.
3. 5: This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated. The fuel pressure should reach a steady value.
4. 6: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.

Fuel Injector Balance Test with Tech 2

The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected when the evaporative emission (EVAP) leak diagnostic completes one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP leak diagnostic completes two test cycles for a large leak or up to eight test cycles for a small leak, only when a condition is detected.

1. Operate the vehicle under the condition of the customers concern. Under high temperature conditions fuel vapors may increase to the point of EVAP canister vapor saturation. Fuel vapors would then be released into the atmosphere. Once the engine is running and EVAP purge is enabled, all fuel vapor release would be eliminated.
2. Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.

1. 3: This step tests for location of fuel leakage in the fuel lines.
2. 4: This step tests for fuel leaks below the fuel level in the fuel tank.
3. 5: This step tests for a location of fuel vapors escaping above the fuel level in the fuel tank.

Fuel Tank Leak Test

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel rail and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.

Alcohol concentrations more than 10 percent in the fuel can be detrimental to fuel system components. Alcohol contamination may cause fuel system corrosion, deterioration of rubber components and subsequent fuel filter restriction. Fuel contaminated with alcohol may cause driveability conditions such as hesitation, lack of power, stalling or no start. Some types of alcohol are more detrimental to fuel system components than others.

Alcohol in Fuel Testing Procedure

The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If alcohol contamination is suspected then use the following procedure to test the fuel quality.

1. Using a 100 ml (3.38 oz.) specified cylinder with 1 ml (0.34 oz.) graduation marks, fill the cylinder with fuel to the 90 ml (3.04 oz.) mark.
2. Add 10 ml (0.34 oz.) of water in order to bring the total fluid volume to 100 ml (3.38 oz.) and install a stopper.
3. Shake the cylinder vigorously for 10-15 seconds.
4. Carefully loosen the stopper in order to release the pressure.
5. Re-install the stopper and shake the cylinder vigorously again for 10-15 seconds.
6. Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer, that now contains both alcohol and water, will be more than 10 ml (0.37 oz.). For example, if the volume of the lower layer is increased to 15 ml (0.51 oz.), this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because this procedure does not extract all of the alcohol from the fuel.

Particulate Contaminants in Fuel Testing Procedure

The fuel sample should be drawn from the bottom of the tank so that any contaminants present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy or contaminated with water as indicated by a water layer at the bottom of the sample, use the following procedure to diagnose the fuel.

1. Using an approved fuel container, draw approximately 0.5 liter (0.53 qt) of fuel.
2. Place the cylinder on a level surface for approximately 5 minutes in order to allow settling of the particulate contamination.

Particulate contamination will show up in various shapes and colors. Sand will typically be identified by a white or light brown crystals. Rubber will appear as black and irregular particles. If particles are found, clean the entire fuel system thoroughly. Refer to Fuel System Cleaning .

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.

Ethanol concentrations of greater than 10 percent can cause driveability conditions and fuel system deterioration. Fuel with more than 10 percent ethanol could result in driveability conditions such as hesitation, lack of power, stalling or no start. Excessive concentrations of ethanol used in vehicles not designed for it may cause fuel system corrosion, deterioration of rubber components and fuel filter restriction.

Test Procedure

1. Test the fuel composition using J 44175 Fuel Composition Tester and J44175-3 Instruction Manual. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2__special-tools) .
2. If water appears in the fuel sample, clean the fuel system. Refer to «Fuel System Cleaning»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2) .
3. Subtract 50 from the reading on the DMM in order to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the Fuel Composition Test Examples table.
4. If the fuel sample contains more than 15 percent ethanol, add fresh, regular gasoline to the vehicle's fuel tank.
5. Test the fuel composition.
6. If testing shows the ethanol percentage is still more than 15 percent, replace the fuel in the vehicle. Refer to «Fuel Tank Draining Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2) .

Fuel Composition Test Examples

An intake manifold runner control (IMRC) valve is used to change the intake manifold plenum configuration. When the IMRC valve is open, the intake manifold is configured to one large plenum. When the IMRC valve is closed, the intake manifold is configured to 2 smaller plenums. The IMRC valve improves engine performance at low and high engine speeds.

Ignition voltage is supplied to the IMRC solenoid. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground or shorted to a voltage by monitoring the feedback voltage.

The ignition voltage circuit and the IMRC control circuit are routed to the IMRC solenoid through an IMRC driver module. The IMRC driver module is an amplifier that is used to strengthen the IMRC solenoid's ability to remain in the commanded position during high load and current demands.

1. Inspect the IMRC solenoid valve for witness marks that indicate that the valve was hitting the intake manifold. This condition may be temperature related.
2. A condition with the IMRC driver module, the wiring from the module to the IMRC solenoid or the solenoid itself will not set a DTC.

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

1. 2: This diagnostic table will only diagnose the IMRC solenoid and the IMRC driver module. If there is a DTC set for the IMRC solenoid, refer to the appropriate DTC table.
2. 5: This step tests the IMRC driver module. The test lamp should turn ON and OFF when commanded with a scan tool. If the test lamp does not turn ON and OFF and there are no IMRC DTCs stored, replace the IMRC driver module.

Intake Manifold Runner Control System Diagnosis

The engine control module (ECM) controls the ignition coils by pulsing the ignition control (IC) circuits, which triggers an ignition coil and fires the spark plug. The ECM controls the sequencing and the timing of each ignition coil. The ignition system consist of the following components

1. The 6 ignition coils
2. The crankshaft position (CKP) sensor
3. The 4 camshaft position (CMP) sensors
4. The ECM

The ignition coils use the following circuits

1. An IC circuit
2. An ignition 1 voltage circuit
3. Two ground circuits

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2) .
3. Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause a condition with the ignition coils.
4. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

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

1. 4: The ignition coils for each bank are fused separately. If a fuse opens or the ignition 1 voltage circuit opens between the fuse and the splice, all the ignition coils for one bank of the engine would be inoperative. If the ground circuit opens at the engine block, the ignition coils would be inoperative for one bank of the engine.
2. 5: This step tests for an open or a high resistance in the ignition 1 voltage circuit of the ignition coil. If the DMM does not display near battery voltage there is an open or a high resistance in the circuit.
3. 6: This step determines if the ground circuit is open. If the circuit is open, the ignition coils would be inoperative for one bank of the engine.
4. 7: This step determines if the ignition 1 voltage circuit is shorted to ground. If the fuse is open, the ignition coils would be inoperative for one bank of the engine.

Electronic Ignition (EI) System Diagnosis

Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the 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 complies with the local area requirements.

Conditions for Updating the I/M System Status

Each system requires at least one and sometimes several, diagnostic tests. The results of these tests are reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed or any one of the DTCs comprising the monitor have illuminated the malfunction indicator lamp (MIL). Once all of the tests are completed, the I/M System Status display will indicate YES in the Completed column. For example, when the heated oxygen sensor (HO2S) Heater Test indicates YES, all of the oxygen sensor heaters have been diagnosed. If the vehicle has four heated oxygen sensors, all four heater circuits have been diagnosed. 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 as part of a service procedure.

Monitored Emission Control Systems

The OBD II system monitors all emission control systems that are on-board. Not all vehicles need every possible emission control system. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following; if equipped

1. Air conditioning system refrigerant
2. Catalytic converter efficiency
3. Comprehensive component monitoring-Emission related inputs and outputs
4. Evaporative emissions (EVAP) system
5. Fuel delivery system
6. Heated catalyst monitoring
7. Misfire monitoring
8. Oxygen sensor system (O2S or HO2S)
9. Oxygen sensor heater system (HO2S Heater)

For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table . Systems such as fuel delivery, misfire and comprehensive components may not be listed in a system status list. These tests run continuously on some vehicles and may not require an indicator.

The I/M System Status display provides an indication of when the control module has completed the required tests. This does not necessarily mean that the test has passed, only that a decision was made. If the diagnostic fails, a DTC will indicate the failure. If a failure indication is present for a DTC associated with one of the I/M regulated systems, it may prevent other required tests from running. For example, a DTC for the control circuit of the EVAP purge solenoid may not be listed in the Inspection/Maintenance System DTC Table because it is a continuous test. If this DTC is set, the Active Tests for the EVAP system may not run.

The I/M System Status information may be useful for a technician to determine if diagnostics have run when verifying repairs.

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

1. 1: Any DTCs set, even those that are not listed in the Inspection/Maintenance System DTC Table, may prevent the required DTCs from running. If there is any question as to whether a set DTC is disabling the required I/M diagnostic, review the Conditions for Running in the diagnostic procedures for the DTC required by the I/M diagnostic. A list of disabling DTCs, if applicable, is contained in the supporting text for that DTC.
2. 2: Anytime a control module is reprogrammed or the diagnostic trouble codes are cleared as part of a repair procedure, all the I/M System Status indicators will reset to NO.
3. 3: Use discretion when determining whether the entire system set procedure needs to be performed. For example, if the only tests that have not run are those that require the engine to be at operating temperature, then only those individual tests need to be run. There is no need to allow the engine to completely cool in order to run these tests.

Inspection/Maintenance (I/M) System Check

The purpose of this procedure is to satisfy the criteria necessary to execute all of the I/M readiness diagnostics. This includes completing the trips for those particular diagnostics. When all diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform this test if more than one of the I/M System Status indicators is set to NO.

Conditions for Running

1. The barometric pressure (BARO) is more than 75 kPa.
2. The engine coolant temperature (ECT) at start-up is less than 42°C (108°F).
3. The intake air temperature (IAT) is between 2-32°C (36-90°F).
4. The battery voltage is between 11-15 volts.
5. The fuel level is between 1/4 and 3/4.

Rough road conditions may prevent some of the tests from running. Extreme high or low ambient temperatures may prevent tests such as heated oxygen sensor (HO2S) heater and evaporative emission (EVAP) system from initiating. If a step is interrupted before completion, perform the remaining portion of the set procedures. Any portion of the set procedure that requires the engine at operating temperature may be repeated. This allows most of the diagnostics to run and the remaining tests can be performed using the individual System Set Procedures.

If the vehicle has recently run, start this procedure at step 3. This will allow the tests that require the engine at operating temperature to run. Using this method allows shorter cool down periods if the tests requiring a cold start do not initiate.

The scan tool can be used to monitor each of the I/M System Status indicators during the I/M Complete System Set Procedure. When all of the indicators for a test step have updated to YES, testing can move on to the next step even if the remaining portion of the test is not complete. For example, step 3 is designed to run the catalyst and HO2S tests. The procedure instructs the technician to operate the vehicle in the enable conditions for 8-10 minutes. If both tests have updated to YES within 4 minutes, it is not necessary to continue with the enable conditions and testing can advance to the next step.

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

1. 1: Make sure you perform the I/M system check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2: This step is to initiate the HO2S heater tests.
3. 3: This step is to run the oxygen sensor and the catalyst tests. The oxygen sensor tests begin once the engine is at operating temperature, in Closed Loop fuel control and a calibrated amount of time has elapsed. The catalyst test will run during the specified cruise period.
4. 4: This step is to run the EVAP tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
5. 5: Perform the individual system test for any of the systems that do not update to YES.
6. 6: The I/M system status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Inspection/Maintenance (I/M) Complete System Set Procedure

Inspection/Maintenance (I/M) System DTC Table

Inspection/Maintenance (I/M) System DTC Table

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. Failure to meet the necessary requirements may produce inaccurate test results.

1. The engine coolant is at operating temperature of 90-100°C (194-212°F).
2. The engine is in closed loop fuel control.

If the status does not update, repeat this test until the I/M System Status updates to YES.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the malfunction indicator lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs).

The first failure of a type B DTC does not constitute a final determination of pass or fail and will not update the I/M System Status to YES. A second trip is required and all the conditions to run must be met in order for the test to run again. These conditions may include a partial to complete engine cool down.

The I/M System Status will update only when an emission related DTC fails the second time or when all of the tests pass.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.

If a diagnostic test is difficult to run, maintain necessary enable conditions until the system status updates to YES.

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

1. 1: Perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2: The Catalyst Test runs during the specified cruise period.
3. 3: This step is to identify a first failure of a type B DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type B DTC. A first failure of a type B DTC will not allow the I/M System Status to update to YES. Refer to «Diagnostic Aids»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
4. 4: This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC.
5. 5: The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Inspection/Maintenance (I/M) Catalyst System Set Procedure

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the evaporative emission (EVAP) system. The test may be used to set the I/M System Status indicators to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing the EVAP System Test. Failure to meet the necessary requirements may produce inaccurate test results.

1. The barometric pressure (BARO) is more than 75 kPa.
2. The engine coolant temperature (ECT) is 0-42°C (32-107°F).
3. The intake air temperature (IAT) is between 2-32°C (36-88°F).
4. The fuel level is between 1/4 and 3/4.
5. The battery voltage is between 11-16 volts.
6. The engine is in Closed Loop fuel control.
7. The vehicle has been driven for 10 minutes for at least 10 km (6 miles) and then the engine idles for 1.0 minute.

1. Extreme high or low ambient temperatures may prevent the EVAP system tests from initiating. Performing a visual inspection prior to running the EVAP Test may prevent having to repeat the test. A loose fuel cap may cause the test to abort or fail and prevent the I/M System Status from updating. A failed or aborted test will require the engine to cool down in order to meet the enable criteria to run another test.
2. The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the malfunction indicator lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs).
3. The first failure of a type B DTC does not constitute a final determination of pass or fail and will not update the I/M System Status to YES. A second and third trip is required and all the conditions to run must be met in order for the test to run again. These conditions require a complete engine cool down before the EVAP I/M ready status changes to YES.
4. The I/M System Status will update only when an emission related DTC fails the second time or when all of the tests pass.
5. If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.
6. If a diagnostic test is difficult to run, maintain necessary enable conditions until the system status updates to YES.

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

1. 1: Make sure you perform the I/M system check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2: The engine coolant temperature must be less than 42°C (107°F) for the EVAP test to run. The ignition can be turned ON to monitor the engine coolant temperature with a scan tool, without starting the engine. This will determine if another test will run. This must be performed 3 times before going to the next portion of the EVAP test.
3. 4: This step is to identify a first failure of a type B DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type B DTC. A first failure of a type B DTC will not allow the I/M System Status to update to YES. Refer to «Diagnostic Aids»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
4. 5: This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC.
5. 6: The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure

The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the oxygen sensor (O2S, HO2S) system. The test may be used to set the I/M System Status to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. Failure to meet the necessary requirements may produce inaccurate test results.

1. The engine OFF time is more than 5 minutes.
2. The ignition 1 voltage is between 11-15 volts.

If the status does not update, repeat this test until the I/M System Status updates to YES.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the malfunction indicator lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs).

The first failure of a type B DTC does not constitute a final determination of pass or fail and will not update the I/M System Status to YES. A second trip is required and all the conditions to run must be met in order for the test to run again. These conditions may include a partial to complete engine cool down.

The I/M System Status will update only when an emission related DTC fails the second time or when all of the tests pass.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.

If a diagnostic test is difficult to run, maintain necessary enable conditions until the system status updates to YES.

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

1. 1: Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2: The oxygen sensor tests begin shortly after the indicated speed is achieved. The engine RPM may be too low in overdrive on manual transmission vehicles. If difficulty is encountered updating the status, operate the vehicle in the recommended gear during the test.
3. 3: This step is to identify a first failure of a type B DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type B DTC. A first failure of a type B DTC will not allow the I/M System Status to update to YES. Refer to «Diagnostic Aids»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
4. 4: This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC.
5. 5: The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any Emission Related DTC sets after the tests are complete, the DTC will require diagnosis.

Inspection/Maintenance (I/M) Heated Oxygen Sensor/Oxygen Sensor (HO2S/O2S) System Set Procedure

The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the heated oxygen sensor (HO2S) system. The test may be used to set the I/M System Status to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. Failure to meet the necessary requirements may produce inaccurate test results.

1. The engine is running.
2. The battery voltage is between 11-15 volts.

The HO2S Heater Tests will normally run within the 2 minutes allotted in the procedure. If there is an indeterminate condition, the test may take up to 8 minutes on some vehicles before a decision of pass or fail is made. If the test does not update within the allotted period of time, continue operation within the enable conditions until the test updates to YES. If the test does not update to YES, it may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent the HO2S Heater Test from initiating. The oxygen sensor heaters are operated by the engine control module (ECM). The control module has the ability to monitor the current required by the heaters and does this on a continuous basis.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the malfunction indicator lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs).

The first failure of a type B DTC does not constitute a final determination of pass or fail and will not update the I/M System Status to YES. A second trip is required and all the conditions to run must be met in order for the test to run again. These conditions may include a partial to complete engine cool down.

The I/M System Status will update only when an emission related DTC fails the second time or when all of the tests pass.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.

If a diagnostic test is difficult to run, maintain necessary enable conditions until the system status updates to YES.

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

1. 1: Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2: Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria. The HO2S Heater Tests may not complete when initiated from a cold start and may require running under a load in order to complete the tests.
3. 3: This step is to identify a first failure of a type B DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type B DTC. A first failure of a type B DTC will not allow the I/M System Status to update to YES. Refer to «Diagnostic Aids»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
4. 4: This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC.
5. 5: The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Inspection/Maintenance (I/M) Heated Oxygen Sensor (HO2S) Heater System Set Procedure

See also:
• Diagnostic System Check - Vehicle
• Scan Tool Data List
• Diagnostic Trouble Code (DTC) List - Vehicle
• Engine Controls Schematics
• Symptoms - Engine Electrical
• Testing for Electrical Intermittents
• Testing for Continuity
• Power and Grounding Component Views
• Symptoms - Theft Deterrent
• Temperature vs Resistance - Engine Coolant Temperature (ECT) Sensor
• Special Tools
• Ignition System Specifications
• Spark Plug Inspection
• DTC P2178
• Loss of Coolant
• Oil Consumption Diagnosis
• Engine Compression Test
• Setting Camshaft Timing
• Camshaft Timing Drive Components Cleaning and Inspection
• Torque Converter Diagnosis Procedure
• Symptoms - HVAC Systems - Automatic
• Knock Sensor (KS) System Description
• DTC P0327 or P0332
• Symptoms - Engine Exhaust
• Symptoms - Automatic Transmission
• Draining and Filling Cooling System (LY7 Static Fill)
• Engine Overheating (LY7)
• DTC P0101
• Symptoms - Instrument Panel, Gages and Console
• Symptoms - Hydraulic Brakes
• DTC P0506 or P0507
• Engine Mount Inspection
• DTC P0850 (3.6L)
• Battery Inspection/Test
• Engine Cranks Slowly
• Engine Control Module (ECM) Connector End Views
• Engine Controls Connector End Views
• Restricted Exhaust
• Wiring Repairs
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• GASOLINE/GASOLINE VAPORS CAUTION
• Lifting and Jacking the Vehicle
• Intake Manifold Replacement - Upper
• Measuring Voltage Drop
• Circuit Testing
• ROAD TEST CAUTION
• DTC P2231
• Hard Start
• Surges/Chuggles
• Lack of Power, Sluggishness or Sponginess
• Detonation/Spark Knock
• Hesitation, Sag, Stumble
• Cuts Out, Misses
• Poor Fuel Economy
• Poor Fuel Fill Quality
• Rough, Unstable or Incorrect Idle and Stalling
• Dieseling, Run-On
• Backfire
• Intermittent Conditions
• Symptoms - Engine Controls
• Important Preliminary Inspections Before Starting
• Inspection/Maintenance (I/M) System DTC Table