Engine Controls - 3.4l (Troubleshooting) Buick Rendezvous I

Important Preliminary Checks Before Starting

Before using the Symptom tables use the following

1. Perform «Diagnostic System Check - Engine Controls»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-diagnostic-information-and-procedures) and verify all of the following items: Ensure no DTCs are stored. Scan tool data is within normal operating range. Refer to «Scan Tool Data List»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-diagnostic-information-and-procedures__scan-tool-data-list) .
2. Verify the customer complaint.
3. Perform the Visual/Physical Check in this section.

Locate the correct symptom in the list at the end of this section. Follow the procedures in the appropriate diagnostic table. If the problem can not be duplicated, or is determined to be intermittent, refer to 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 problem without further tests and can save valuable time. This inspection should include the following areas

1. Inspect the PCM grounds for being clean, tight, and in their proper location. Refer to «Master Electrical Component List»(/buick/rendezvous/i-2001-2007/remont/electrical-component-locations/#wiring-systems-component-locator__master-electrical-component-list) and «Power and Grounding Component Views»(/buick/rendezvous/i-2001-2007/remont/electrical-component-locations/#wiring-systems-component-locator) in Wiring Systems.
2. Inspect vacuum hoses for splits, kinks, and proper connections, as shown on Vehicle Emission Control Information label. Inspect thoroughly for any type of leak or restriction. Refer to «Emission Hose Routing Diagram»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-introduction-service-replacement) .
3. Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking, especially between the (MAF) sensor and the throttle body.
4. Inspect for air leaks at throttle body mounting area, MAF sensor and intake manifold sealing surfaces.
5. Inspect the wiring harness for poor connections, pinches, cuts, or other damage.
6. Inspect for loose, damaged, or missing sensors/components.

Use the following tables when diagnosing a symptom complaint

1. «Hard Start»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__hard-start)
2. «Surges/Chuggles»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__surgeschuggles)
3. «Lack of Power, Sluggishness, or Sponginess»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__lack-of-power-sluggishness-or-sponginess)
4. «Detonation/Spark Knock»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__detonationspark-knock)
5. «Hesitation, Sag, Stumble»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__hesitation-sag-stumble)
6. «Cuts Out, Misses»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__cuts-out-misses)
7. «Poor Fuel Economy»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__poor-fuel-economy)
8. «Poor Fuel Fill Quality»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__poor-fuel-fill-quality)
9. «Rough, Unstable, or Incorrect Idle and Stalling»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__rough-unstable-or-incorrect-idle-and)
10. «Dieseling, Run-On»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__dieseling-run-on)
11. «Backfire»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__backfire)
12. «Engine Cranks but Does Not Run»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting)

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

Circuit Description

Ignition voltage is supplied to the malfunction indicator lamp (MIL). The powertrain control module (PCM) turns the MIL ON by grounding the MIL control circuit. There should be a steady MIL with the ignition ON and the engine OFF.

MIL Operation

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

MIL Function

1. The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
2. The MIL illuminates during a bulb test and a system test.
3. A DTC will be stored if a MIL is requested by the PCM.

MIL Illumination

1. The MIL will illuminate with ignition switch ON and the engine not running.
2. The MIL will turn OFF when the engine is started.
3. The MIL will remain ON if the self-diagnostic system has detected a malfunction.
4. The MIL may turn OFF if the malfunction is not present.
5. If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
6. If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.

Test Description

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

1. 4: This step tests for a short to voltage on the MIL control circuit. With the fuse removed there should be no voltage on the MIL control circuit.

Malfunction Indicator Lamp (MIL) Inoperative

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

The MIL is located on the instrument panel (IPC).

MIL Function

1. The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
2. The MIL illuminates during a bulb test and a system test.
3. A DTC will be stored if a MIL is requested by the diagnostic.

MIL Illumination

1. The MIL will illuminate with ignition switch ON and the engine not running.
2. The MIL will turn OFF when the engine is started.
3. The MIL will remain ON if the self-diagnostic system has detected a malfunction.
4. The MIL may turn OFF if the malfunction is not present.
5. If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
6. If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.

Diagnostic Aids

If the problem is intermittent, refer to Intermittent Conditions .

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

1. 2: This step determines if the condition is with the MIL control circuit or the PCM.

Malfunction Indicator Lamp (MIL) Always On

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/rendezvous/i-2001-2007/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. The engine cranking speed is acceptable. Refer to «Engine Cranks Slowly»(/buick/rendezvous/i-2001-2007/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) in Engine Electrical.
3. There is adequate fuel in the fuel tank.

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

1. 3: This step determines if the ignition relay is providing the listed fuses with voltage.
2. 5: This step determines if the fuel pump is operating electrically.
3. 6: If all the Cylinder Injector Circuit Status parameters display Fault, this indicates a condition with the injector supply voltage circuit.

Engine Cranks but Does Not Run

The ignition relay is normally an open relay. The relay armature is held in the open position by spring tension. When the ignition switch is turned to the Run or Start position, current will flow through the relay coil. A wire connected to the other end of the relay coil completes the path to ground. The electromagnetic field created by the relay coil overcomes the spring tension and moves the armature, allowing the relay contacts to close. The closed relay contacts allow current to flow from the battery to the following fuses

1. The Eng Controls fuse
2. The Fuel INJ fuse
3. The Elec Eng fuse
4. The O2 Sensors fuse
5. The Trans Sol fuse
6. The ABS fuse
7. The AWD fuse

When the ignition switch is turned to the OFF position, the electromagnetic field collapses. This action allows the spring tension to move the armature away from the relay contacts, which interrupts current flow to the fuses.

If the ignition relay fails to close, the engine will crank but will not run. The class 2 communications will be available with the use of a scan tool.

The ignition relay table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.

Ignition Relay 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.

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.

If the condition is intermittent, 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. 4: This step verifies that the PCM is providing voltage to the fuel pump relay.
4. 5: This step tests for an open in the fuel pump relay ground circuit.
5. 6: This step determines if a voltage is constantly being applied to the fuel pump relay.
6. 12: This tests for a grounded fuel pump supply voltage circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump supply voltage circuit.
7. 15: This step jumps the fuel pump relay in order to activate the fuel pump.
8. 16: This step tests for an open in the fuel pump feed circuit between the in-line connector and the fuel pump relay.
9. 17: This step tests for an open or high resistance in the fuel pump ground circuit.
10. 20: 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 Diagnosis

System Description

When the ignition is turned ON, the powertrain control module (PCM) will turn ON the in-tank fuel pump. The in-tank fuel pump will remain ON as long as the engine is cranking or running and the PCM is receiving ignition reference pulses. If there are no ignition reference pulses, the PCM will turn the in-tank fuel pump OFF 2 seconds after the ignition is turned ON or 2 seconds after the engine stops running.

The in-tank fuel pump is an electric pump attached to the fuel sender assembly. The fuel pump is designed to provide fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate fuel return pipe.

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. 6: This step tests the fuel pressure regulator. The fuel pressure regulator is controlled by engine vacuum. With engine vacuum applied, the pressure should drop the specified value.
4. 9: This step inspects the fuel pressure regulator for a fuel leak from the vacuum port. If fuel leaks from the fuel pressure regulator while the fuel pump is commanded ON, replace the fuel pressure regulator.
5. 10: This step tests for a loss of fuel pressure between the fuel feed pipe shut off adapter and the fuel pump.
6. 11: This step tests for a leaking fuel injector, or fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.
7. 14: This step tests for a restricted fuel return pipe. If the fuel pressure is within the specified values, a restriction in the fuel return pipe is indicated.
8. 16: This step determines if the fuel pressure regulator, or the fuel pump, is the cause of the low fuel pressure. If the pressure rises above the specified value, the fuel pump is OK.
9. 18: 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. The control module 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/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting) or «Fuel Injector Balance Test with Tech 2»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-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. 6: This step determines if the ignition 1 voltage circuit under the intake plenum is causing the concern.
4. 8: 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 136

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 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 Tech 2

The powertrain control module (PCM) enables the appropriate fuel injector on the intake stroke for each cylinder. A 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.

1. Monitoring the fuel injector circuit status with a scan tool, while moving the fuel injector harness, may help isolate an intermittent condition.
2. Performing the Fuel Injector Coil Test may help isolate an intermittent condition. Refer to «Fuel Injector Coil Test»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__intermittent-conditions) .

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

1. 4: This step tests for a short to ground on the ignition 1 voltage supply circuit of the fuel injector.
2. 5: This step tests for a short to a PCM ground on the ignition 1 voltage supply circuit of the fuel injector.
3. 6: This step tests for an open between the multi-way connector and the fuel injectors.
4. 7: This step tests for an open or high resistance between the multi-way connector and the fuel injectors.

Fuel Injector Circuit Diagnosis

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) diagnostics completes one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics completes two test cycles.

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. Test for fuel leaking in the following locations: The fuel tank The fuel feed and return pipes
3. Test for fuel vapor leaks in the following locations: The fuel tank, fill limiter vent valve, and rollover valves The fuel fill pipe, hose, and fuel fill cap The fuel sender housing and seal The fuel tank pressure (FTP) sensor seal The EVAP vapor pipe
4. Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.

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

1. 1: Perform this procedure to determine that no EVAP diagnostic trouble code (DTC) is present.
2. 3: This test is to locate fuel leakage in the fuel lines.
3. 4: This tests for fuel leaks below the fuel tank fuel level.
4. 5: This test is to locate 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 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.
2. If water appears in the fuel sample, perform the following steps: Clean the fuel system. Refer to «Fuel System Cleaning»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-introduction-service-replacement__fuel-system-cleaning) . Replace the fuel filter. Refer to «Fuel Filter Replacement»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-introduction-service-replacement) .
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 System Cleaning»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-introduction-service-replacement__fuel-system-cleaning) .

Fuel Composition Test Examples

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, use the following procedure to test the fuel quality

1. Fill the cylinder with fuel to the 90 ml mark using a 100 ml specified cylinder with 1 ml graduation marks.
2. Add 10 ml of water 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 to release the pressure.
5. 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 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. Draw approximately 0.5 liter of fuel using an approved fuel container.
2. Place the cylinder on a level surface for approximately 5 minutes to allow settling of the particulate contamination.

Particulate contamination will show up in various shapes and colors. Sand will typically be identified by 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.

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

1. 4: This step tests the ability of the MAP sensor to correctly indicate BARO.

1. 12: The measurement noted in this step will be used in subsequent steps if the measurement does not exceed the specified value.

1. 15: This step calculates the resistance in the 5-volt reference circuit.

1. 16: This step calculates the resistance in the low reference circuit.

Manifold Absolute Pressure (MAP) Sensor Diagnosis

The engine idle speed is controlled by the idle air control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by 2 circuits from the powertrain control module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed diagnostic trouble code (DTC) sets.

Inspect for the following conditions

1. High resistance in an IAC valve control circuit
2. The correct positive crankcase ventilation (PCV) valve, properly installed and proper operation of the PCV valve
3. Proper operation and installation of all air intake components
4. Proper installation and operation of the mass air flow (MAF) sensor, if equipped
5. A tampered with or damaged throttle stop screw
6. A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped
7. A skewed high throttle position (TP) sensor
8. Excessive deposits in the IAC passage or on the IAC pintle
9. Excessive deposits in the throttle bore or on the throttle plate
10. Vacuum leaks
11. A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve. Refer to «Symptoms - Engine Controls»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting) .
12. If the problem is determined to be intermittent, refer to «Intermittent Conditions»(/buick/rendezvous/i-2001-2007/remont/testing-diagnostics/#engine-controls-34l-troubleshooting__intermittent-conditions) .

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

1. 5: This test will determine the ability of the PCM and IAC valve control circuits to control the IAC valve.
2. 7: This test will determine the ability of the PCM to provide the IAC control valve circuits with a ground. On a normally operating system, the test lamp should not flash while the IAC Counts are incrementing.

Idle Air Control (IAC) System Diagnosis

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

1. The IC timing signal circuit
2. The IC timing control circuit
3. The low-resolution engine speed signal circuit
4. A low reference signal circuit

The ICM sends 3X signals to the PCM. The ICM controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions

1. The PCM receives the second 3X signal.
2. The PCM applies 5 volts to the IC timing signal circuit.

Electronic Ignition (EI) System Diagnosis

The ignition system uses 2 different types of crankshaft position (CKP) sensors. The ignition control module (ICM) has independent power and ground circuits. The CKP sensor B is used above 1650 RPM. The CKP sensor B provides the ICM with 7X signals. A signal converter within the ICM produces digital 3X pulses to the powertrain control module (PCM). The 3X signal is passed to the PCM on the low resolution engine speed signal circuit. The CKP sensor B is connected directly to the ICM, and consists of the following circuits

1. The CKP sensor signal circuit
2. The low reference circuit

The CKP sensor A connects directly to the PCM, and consists of the following circuits

1. The 12-volt reference circuit
2. The medium resolution engine speed signal circuit
3. The low reference circuit

The CKP sensor system diagnosis is used to diagnose a fault with CKP sensor B or any of the CKP sensor B circuits.

Crankshaft Position Sensor (CKP) 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 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 comprising 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. Not all vehicles have a full complement of emission control systems. 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

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

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 and do not require an I/M System Status indicator.

Inspection/Maintenance (I/M) System Check

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 diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform this test when more than one or all of the I/M System Status indicators are set to NO.

Conditions for Running

Cold Start

1. The barometric pressure is more than 65 kPa.
2. The engine coolant temperature (ECT) is below 35°C (95°F).
3. The intake air temperature (IAT) is below 35°C (95°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.

Rough road conditions may prevent some of the tests from running. Extreme high or low ambient temperatures may prevent tests such as HO2S Heater and 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.

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 EVAP, AIR, and HO2S tests. The procedure instructs the technician to operate the vehicle in the enable conditions for 6 minutes. If all 3 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. 2: This step is to run the HO2S Heater Tests and initiate the EVAP System Test. Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria.
2. 3: This step is to run the EVAP, AIR and the Oxygen Sensor Tests. The EVAP Test begins once the engine coolant reaches a calibrated temperature. The AIR Test, if equipped, begins shortly after Closed Loop and the indicated speed is achieved. 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.
3. 4: This step is to run the EGR Tests. The EGR Tests are run during a gradual deceleration with a closed throttle. The vehicle speed is required in order to maintain a high, steady MAP signal.
4. 5: This step is to run the Catalyst Tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
5. 7: 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 inspection/maintenance (I/M) readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. 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 other tests for that system have not run.

1. The engine has been running longer than 10 minutes.
2. The engine load must be stable.
3. The idle air control (IAC) position parameter does not change more than 5 counts.
4. The throttle position (TP) is below 1.5 percent.
5. The short term FT is between -20 and +20 percent.
6. The transaxle is in drive for automatic transaxles, or in neutral for manual transaxles with the clutch pedal depressed.
7. The barometric pressure is more than 74 kPa.
8. The engine coolant temperature (ECT) is between 75-126°C (167-258.8°F).
9. The engine is in Closed Loop fuel control.
10. The battery voltage is more than 10.7 volts.
11. The intake air temperature (IAT) is between -20 and +100°C (-4 and +212°F).
12. The difference between the engine speed and the desired engine speed is less than 200 RPM.
13. The mass air flow (MAF) is between 3-10 grams per second.

The control module runs a maximum of 6 tests per trip until the Catalyst System Status updates to YES. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

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 A/C compressor clutch turning ON may cause the test to abort.

Inspection/Maintenance (I/M) Catalyst 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 exhaust gas recirculation (EGR) system. The test may be used to set the I/M System Status indicators to YES. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. 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 other tests for that system have not run.

1. The barometric pressure is more than 74 kPa.
2. The ignition 1 voltage is between 11-18 volts.
3. The intake air temperature (IAT) is between 0-100°C (32-212°F).
4. The A/C Relay Command parameter does not change.
5. The Current Gear parameter does not change.
6. The engine coolant temperature (ECT) is more than 75°C (167°F).
7. The engine speed is between 1,050-1,400 RPM.
8. The manifold absolute pressure (MAP) is between 15-70 kPa.
9. The mass air flow (MAF) sensor does not change more than 2 grams per second.
10. The throttle position (TP) sensor is less than one percent.
11. The vehicle speed is more than 48 km/h (30 mph) during deceleration.
12. The idle air control (IAC) position does not change more than 5 counts when the above conditions are met.

The control module only runs the EGR Active Tests during a gradual deceleration with a closed throttle and a vehicle speed above 48 km/h (30 mph). Several deceleration cycles may be necessary in order to accumulate a sufficient number of EGR flow samples. The procedure outlined in the table is for a clear, flat road. If the procedure is performed on a road with a slight down hill grade, the test may acquire the necessary sample counters in one or two decel trips. If the test is interrupted during the procedure, it may take more than three deceleration cycles to complete the test. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

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 A/C compressor clutch turning ON may cause the test to abort.

If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the System Status updates to YES.

Inspection/Maintenance (I/M) Exhaust Gas Recirculation (EGR) 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 evaporative emission (EVAP) system. The test may be used to set the I/M System Status indicators to YES. The I/M System Status display on the scan tool indicates whether or not the control module has completed the required test. The required test is complete when either all of the DTCs comprising the test have run and passed, or when any one of the DTCs comprising the test has illuminated the malfunction indicator lamp (MIL). Once the test is complete, the I/M System Status display will indicate YES in the completed column. Performing a visual inspection prior to running the EVAP test may prevent having to repeat the test due to the fact that a failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.

1. The barometric pressure is more than 75 kPa.
2. The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
3. The fuel level is between 15-85 percent.
4. The battery voltage is between 10-18 volts.
5. The intake air temperature (IAT) is between 4-30°C (39-86°F).
6. The startup ECT and IAT are within 9°C (16°F) of each other.
7. The vehicle speed sensor (VSS) is less than 121 km/h (75 mph).

Extreme high or low ambient temperatures may prevent the EVAP System Tests from initiating.

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 A/C compressor clutch turning ON may cause the test to abort.

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

The purpose of this test is to satisfy the enable criteria necessary to execute 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. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. 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 other tests for that system have not run.

1. The engine coolant temperature (ECT) is less than 35°C (95°F).
2. The engine is running in Closed Loop fuel control.
3. The engine has been running for more than 1 minute.
4. The battery voltage is between 9-18 volts.
5. The mass air flow (MAF) is between 15-31 grams per second.
6. The engine speed is between 1,300-3,000 RPM.
7. The throttle position (TP) sensor is more than 2 percent.
8. The vehicle speed sensor (VSS) is between 33-120 km/h (20-75 mph).
9. The short term fuel trim is between 97.5-102.5.
10. The intake air temperature (IAT) is less than 35°C (95°F).
11. The startup engine coolant temperature (ECT) and IAT are within 6°C (10.8°F) of each other.

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 A/C compressor clutch turning ON may cause the test to abort.

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. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. 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 other tests for that system have not run.

1. The engine coolant temperature (ECT) is less than 35°C (95°F).
2. The intake air temperature (IAT) is less than 35°C (95°F).
3. The difference between the IAT and the ECT is less than 6°C (10.8°F).
4. The battery voltage is between 10-18 volts.
5. The engine speed is between 600-3,000 RPM.
6. The mass air flow (MAF) is between 4-26 grams per second.

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 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.

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 A/C compressor clutch turning ON may cause the test to abort.

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

The evaporative emission (EVAP) Service Bay Test raises the engine coolant temperature (ECT) threshold so that the temperature sensitive EVAP diagnosis tests can run while in service environments. When the EVAP tests are run the service bay test will indicate a pass or will indicate a specific DTC has failed. The EVAP service bay test can be used to verify an existing condition and verify that the EVAP system is OK after a repair is completed.

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.

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.

See also:
• Diagnostic System Check - Engine Controls
• Scan Tool Data List
• Master Electrical Component List
• Power and Grounding Component Views
• Emission Hose Routing Diagram
• Testing for Intermittent Conditions and Poor Connections
• Power Distribution Schematics
• Checking Aftermarket Accessories
• Diagnostic System Check - Engine Electrical
• Powertrain Control Module (PCM) Replacement
• Temperature vs Resistance
• DTC P0117
• DTC P0506
• Spark Plug Inspection
• Oil Consumption Diagnosis
• Engine Compression Test
• DTC P0172
• Torque Converter Diagnosis Procedure
• Ignition System Specifications
• Cooling System Description and Operation
• Symptoms - Engine Mechanical
• Symptoms - Instrument Panel, Gages and Console
• Base Engine Misfire without Internal Engine Noises
• Wiring Repairs
• Engine Controls Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Diagnostic System Check - Instrument Cluster
• Circuit Testing
• Connector Repairs
• Diagnostic Trouble Code (DTC) List
• Engine Cranks Slowly
• Restricted Exhaust
• Probing Electrical Connectors
• Circuit Protection - Fusible Links
• Ignition Switch Replacement
• Fuel Pressure Gage Installation and Removal
• Fuel Pressure Relief Procedure
• Testing for Continuity
• Fuel Injector Cleaning Procedure
• Lifting and Jacking the Vehicle
• Fuel System Cleaning
• Altitude vs Barometric Pressure
• Crankshaft and Bearings Cleaning and Inspection
• Road Test Caution
• Intermittent Conditions
• 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
• Engine Cranks but Does Not Run
• Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)
• Inspection/Maintenance (I/M) System DTC Table