Engine Control System - 3.5L - Troubleshooting: Diagnosis Pontiac G6 I

Important Preliminary Inspections Before Starting

Before using the Symptom tables, perform the following

1. Perform «Diagnostic System Check - Vehicle»(ref-242980-S19231637582006082100000) 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»(ref-243059-S35183172092006082100000) .
2. Verify the customer concern.
3. Perform the «Visual/Physical Check»(ref-243025-S11756538572006082100000) . 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.

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 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 a good 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 good ground. If the MIL does not illuminate, test the MIL control circuit for an open or high resistance. If the MIL control circuit tests OK, replace the IPC. If the MIL does illuminate, but does not when commanded ON with a scan tool, replace the ECM.

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»(ref-242980-S20451683192006082100000) : 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»(ref-243025-S00828068912006082100000) .
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 «Electronic Ignition (EI) System Diagnosis»(ref-243025-S00828068912006082100000) .
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»(ref-243047-S19836103572006082100000) .
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»(ref-243026-S36270575562006082100000) .
8. Turn OFF the ignition.
9. Install the J 34730-1A 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 380-410 kPa (55-60 psi). If the fuel pressure is not within 380-410 kPa (55-60 psi) refer to «Fuel System Diagnosis»(ref-243025-S42673721662006082100000) .
10. Inspect for the following conditions: Compare the actual engine coolant temperature to the ECT parameter. Refer to «DTC P0116, P0125, OR P0128»(ref-243042-S03727015222006082100000) . Air filter and air intake system for restrictions and obstructions Test the fuel for contamination. Refer to «Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)»(ref-243025-S06924987942006082100000) . Inspect the spark plug and spark plug wires. Refer to «Spark Plug Inspection»(ref-242989-S12052747542006082100000) . Test the exhaust system for restrictions. Refer to «Restricted Exhaust»(ref-243054-S19494961302006082100000) .

Circuit Description

The crankshaft position (CKP) sensor is a 24X sensor. It provides 24 digital ON/OFF signals to the powertrain control module (PCM) per revolution of the crankshaft. This information is used by the PCM for ignition timing, fuel injector timing, misfire diagnostics, and tachometer display. The PCM supplies 12 volts to the sensor on the 12-volt reference circuit, and provides a ground on the low reference circuit. The CKP sensor provides signals to the PCM on the medium resolution engine speed signal circuit.

Diagnostic Aids

A faulty CKP sensor, CMP sensor, or a short to ground on either 12-volt reference circuit may cause the CKP signal to be lost, preventing the engine from running.

When the ignition is turned ON, the powertrain control module (PCM) turns ON the fuel pump relay, which turns ON the in-tank fuel pump. The in-tank fuel pump remains ON as long as the engine is cranking or running and the PCM is receiving reference pulses. If there are no reference pulses, the PCM turns the in-tank fuel pump OFF 2 seconds after the ignition is turned ON or 2 seconds after the PCM no longer receives reference pulses.

1. Inspect the ground connection for the fuel pump. Ensure all ground connections are clean and tight.
2. The following conditions may have caused the fuel pump fuse to open: The fuse is faulty. There is an intermittent short in the fuel pump power feed circuit. The fuel pump has an intermittent internal problem.
3. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-242973-S38322986792006082100000) .

Component Testing

Fuel Injector Coil Test

Verify the resistance of each fuel injector with one of the following methods

1. If the engine coolant temperature (ECT) sensor is between 10-32°C (50-90°F), the resistance of each fuel injector should be 11-14 ohms. If the injectors measure OK, perform the AFIT Test Procedure. If not within the specified range, replace the fuel injector.
2. If the ECT sensor is not between 10-32°C (50-90°F), measure and record the resistance of each fuel injector with a DMM. Subtract the lowest resistance value from the highest resistance value. The difference between the lowest value and the highest value should be equal to or less than 3 ohms. If the difference is equal to or less than 3 ohms, refer to AFIT Test Procedure for further diagnosis of the fuel injectors. If the difference is more than 3 ohms, add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Compute the difference between the highest individual fuel injector resistance value and the average resistance value. Replace the fuel injector that displays the greatest difference above or below the average.

AFIT Test Procedure

1. Turn OFF all accessories.
2. Turn OFF the ignition.
3. Install the AFIT. Refer to the AFIT User Guide.
4. Turn ON the AFIT and select the vehicle.
5. Turn ON the ignition and perform the Injector Test. If the AFIT aborts testing due to fuel pressure or fuel leak down, refer to «Fuel System Diagnosis»(ref-243025-S42673721662006082100000) .
6. View the test results. If any injector exceeds the recommended tolerance, replace the injector(s).

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

FUEL INJECTOR REPLACEMENT

1. Monitoring the misfire current counters, or misfire graph, may help to 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 customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.

Fuel Injector Coil Test

Verify the resistance of each fuel injector with one of the following methods

1. If the engine coolant temperature (ECT) sensor is between 10-32°C (50-90°F), the resistance of each fuel injector should be 11-14 ohms. If the injectors measure OK, perform the Fuel Injector Balance Test-Fuel Pressure Test. If not within the specified range, replace the fuel injector.
2. If the ECT sensor is not between 10-32°C (50-90°F), measure and record the resistance of each fuel injector with a DMM. Subtract the lowest resistance value from the highest resistance value. The difference between the lowest value and the highest value should be equal to or less than 3 ohms. If the difference is equal to or less than 3 ohms, refer to Fuel Injector Balance Test-Fuel Pressure Test for further diagnosis of the fuel injectors. If the difference is more than 3 ohms, add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Compute the difference between the highest individual fuel injector resistance value and the average resistance value. Replace the fuel injector that displays the greatest difference above or below the average.

Fuel Injector Balance Test-Fuel Pressure Test

1. Install a fuel pressure gage. Refer to «FUEL PRESSURE GAGE INSTALLATION AND REMOVAL»(ref-242989-S40680608532006082100000) .
2. Turn ON the ignition, with the engine OFF.
3. Command the fuel pump relay ON with a scan tool.
4. Observe the fuel pressure gage with the fuel pump commanded ON. The fuel pressure should be 384-425 kPa (56-62 psi). If the fuel pressure is not 384-425 kPa (56-62 psi), refer to «Fuel System Diagnosis»(ref-243025-S42673721662006082100000) .
5. Monitor the fuel pressure gage for one minute. The fuel pressure should not decrease more than 34 kPa (5 psi). If the fuel pressure decreases more than 34 kPa (5 psi), refer to «Fuel System Diagnosis»(ref-243025-S42673721662006082100000) .
6. Perform the Fuel Injector Balance Test with Special Tool or the Fuel Injector Balance Test with Tech 2.

Fuel Injector Balance Test with Special Tool

1. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position.
2. Disconnect the multi-way harness connector of the fuel injectors.
3. Connect the J 39021 , the J 39021-210 , and the J 39021-410 to the fuel injector multi-way connector.
4. Command the fuel pump relay ON and then OFF three times with a scan tool. On the last command, as the fuel pressure begins to slowly degrade and stabilize, select a fuel pressure within 34 kPa (5 psi) of the maximum pump pressure. Record this fuel pressure. This is the starting pressure at which you will pulse each injector.
5. Command the fuel pump relay ON one more time and energize the fuel injector by depressing the Push to Start Test button on the J 39021 at the previously selected pressure.
6. After the injector stops pulsing, select Min from the Display Mode and record the Min pressure.
7. Clear the Min/Max results.
8. Select Normal from the Display Mode.
9. Repeat steps 5 through 8 for each fuel injector.
10. Perform the Pressure Drop Calculation.

Fuel Injector Balance Test with Tech 2

1. Command the fuel pump relay ON and then OFF three times with a scan tool. On the last command, as the fuel pressure begins to slowly degrade and stabilize, select a fuel pressure within 34 kPa (5 psi) of the maximum pump pressure. Record this fuel pressure. This is the starting pressure at which you will pulse each injector.
2. With a scan tool, select the Fuel Injector Balance Test function within the Special Functions menu.
3. Select an injector to be tested.
4. Press Enter to prime the fuel system.
5. Energize the fuel injector by depressing the Pulse Injector button on the scan tool at the previously selected pressure.
6. After the injector stops pulsing, select Min from the Display Mode on the CH-48027 and record the Min pressure.
7. Clear the Min/Max results on the CH-48027 .
8. Select Normal from the Display Mode on the CH-48027 .
9. Press Enter on the scan tool to bring you back to the Select Injector screen.
10. Repeat steps 3 through 9 for each fuel injector.
11. Perform the Pressure Drop Calculation.

Pressure Drop Calculation

1. Subtract the minimum pressure from the starting pressure for one fuel injector. The result is the pressure drop value.
2. Obtain a pressure drop value for each fuel injector.
3. Add all of the individual pressure drop values except for the injector suspected of being faulty. This is the total pressure drop.
4. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be more than 20 kPa (3 psi). If the difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the fuel injector.

The powertrain control module (PCM) enables the appropriate fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The PCM 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»(ref-243025-S27832649812006082100000) or «Fuel Injector Balance Test with Tech 2»(ref-243025-S17297701022006082100000) .

The scan tool first energizes the fuel pump and then the fuel 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)

Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)

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 of 10 percent or greater in 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 specified cylinder with 1 ml graduation marks, fill the cylinder with fuel to the 90 ml mark.
2. Add 10 ml of water in order to bring the total fluid volume to 100 ml 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, which would now contain both alcohol and water, will be more than 10 ml. For example, if the volume of the lower layer is increased to 15 ml, 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 water 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 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 .

The manifold absolute pressure (MAP) sensor responds to changes in intake manifold pressure which gives an indication of the engine load. The MAP sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit and provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit, which is relative to the pressure changes in the manifold. With low MAP, such as during idle or deceleration, the PCM should detect a low MAP sensor signal voltage. With high MAP, such as ignition ON, engine OFF or wide open throttle (WOT), the PCM should detect a high MAP sensor signal voltage. The MAP sensor is also used in order to calculate the barometric pressure (BARO) 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 PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 sets. If the PCM detects a MAP sensor signal voltage that is excessively high DTC P0108 sets.

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

There are 3 dual-tower ignition coils that are part of the ignition control module (ICM). The ICM contains coil driver circuits that command the coils to operate. The ICM has the following circuits

1. An ignition voltage circuit
2. A ground
3. An ignition control (IC) 1 control circuit for the 1-4 ignition coil
4. An IC 2 control circuit for the 2-5 ignition coil
5. An IC 3 control circuit for the 3-6 ignition coil
6. A low reference circuit

The powertrain control module (PCM) controls each dual-tower ignition coil by transmitting timing pulses on the ignition coil control circuit to the ICM for the proper coil to enable a spark event.

Electronic Ignition (EI) System Diagnosis

Conditions for Running

Cold Start

1. The barometric pressure (BARO) is more than 74 kPa.
2. The engine coolant temperature (ECT) is below 30°C (86°F).
3. The intake air temperature (IAT) is between 4-30°C (39-86°F).
4. The difference between the IAT and the ECT is 6°C (10.8°F) or less.
5. The battery voltage is between 10-18 volts.
6. The fuel level is between 15-85 percent.

Inspection/Maintenance (I/M) System DTC Table

Inspection/Maintenance (I/M) System DTC Table

Conditions for Running the Test

1. The ignition is ON.
2. The battery voltage is between 9-18 volts.
3. The engine coolant temperature (ECT) is less than 70°C (158°F).
4. The fuel level is 15-85 percent of capacity.
5. The vehicle speed is less than 4.8 km/h (3 mph).
6. Stored DTCs have been cleared.

Test Procedure

1. Install a scan tool.
2. With a scan tool, select the service bay test in the special functions menu.
3. Follow the instructions on the scan tool.
4. Check DTCs with a scan tool.
5. Continue with the published service manual diagnostic DTC procedure.