Engine Control System (Troubleshooting) - 3.5l (lx9) Chevrolet Malibu VI

Important Preliminary Inspections Before Beginning

Perform Diagnostic System Check - Vehicle in Vehicle DTC Information before using the symptom tables and verify that all of the following are true

1. The control module and malfunction indicator lamp (MIL) are operating correctly.
2. There are no DTCs stored.
3. The scan tool data is within the normal operating range, refer to «Scan Tool Data List»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-diagnosis-information-procedures-35l-lx9__scan-tool-data-list) .
4. Verify the customer concern and locate the correct symptom in the table of contents. Inspect the items indicated under that symptom.

Visual/Physical Inspection

Several of the symptom procedures ask for a careful visual and physical inspection. This step is extremely important. The visual and physical inspection can lead to correcting a problem without further inspections and can save valuable time. Ensure that

1. The control module grounds are clean, tight and in the proper location.
2. The vacuum hoses are not split or kinked and properly connected, as shown on the Vehicle Emission Control Information label. Inspect thoroughly for any type of leak or restriction.
3. The mass air flow (MAF) sensor is properly installed.
4. The air intake ducts are not collapsed or damaged.
5. There are no leaks at the throttle body mounting area, the MAF sensor, or the intake manifold sealing surfaces.
6. The ignition wires are not cracked, brittle, or carbon tracked.
7. The engine harness wiring and terminals are properly connected and are not pinched or cut.

Intermittent

Faulty electrical connections or wiring cause most intermittent problems. Perform a careful visual and physical inspection of the suspect connectors for the following conditions

1. Improperly mated connector halves
2. Terminals that are not seated
3. Terminals that are damaged or improperly formed

Reform or replace connector terminals in the problem circuit in order to ensure proper contact tension. Refer to Connector Repairs in Wiring Systems. Remove the terminal from the connector body in order to inspect for poor terminal wire connection. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Road test the vehicle with the DMM connected to the suspected circuit. An abnormal reading that occurs when the malfunction occurs is a good indication that there is a malfunction in the circuit being monitored.

Use a scan tool in order to help detect intermittent conditions. Useful features of the GM scan tool include the following

1. Trigger the Snapshot feature in order to capture and store engine parameters when the malfunction occurs. Review this stored information in order to see the specific running conditions that caused the malfunction.
2. Freeze Frame/Failure Records can also aid in locating an intermittent condition. Review and capture the information in the Freeze Frame/Failure Record associated with the intermittent DTC being diagnosed. Drive the vehicle within the conditions that were present when the DTC originally set.
3. Use the Plot Function on the scan tool in order to plot selected data parameters. Review this stored information to aid in locating an intermittent problem. Refer to the scan tool Users Guide for more information.

Any of the following may cause an intermittent malfunction indicator lamp (MIL) with no stored DTC

1. The ignition coils are shorted to a ground or arcing at the ignition wires or the spark plugs.
2. The control module grounds are loose or dirty. Refer to «Engine Controls Schematics»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-introduction-35l-lx9) .
3. The ignition control (IC) wires are routed too close to the secondary ignition wires, coils, or the generator. Ensure that all of the circuits from the control module to the ignition coils have good connections.
4. There is an open diode across the A/C compressor clutch or any other open diodes.

Use the following tables when diagnosing a symptom complaint

1. «Hard Start»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__hard-start)
2. «Surges/Chuggles»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__surgeschuggles)
3. «Lack of Power, Sluggishness, or Sponginess»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__lack-of-power-sluggishness-or-sponginess)
4. «Detonation/Spark Knock»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__detonationspark-knock)
5. «Hesitation, Sag, Stumble»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__hesitation-sag-stumble)
6. «Cuts Out, Misses»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__cuts-out-misses)
7. «Poor Fuel Economy»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__poor-fuel-economy)
8. «Poor Fuel Fill Quality»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__poor-fuel-fill-quality)
9. «Rough, Unstable, or Incorrect Idle and Stalling»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__rough-unstable-or-incorrect-idle-and)
10. «Dieseling, Run-On»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__dieseling-run-on)
11. «Backfire»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__backfire)

Intermittent Conditions

Intermittent Conditions

Hard Start

Hard Start

Surges/Chuggles

Surges/Chuggles

Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

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.

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

Battery positive voltage is supplied directly 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

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»(/chevrolet/malibu/vi-2003-2006/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. The engine cranking speed is acceptable. Refer to «Engine Cranks Slowly»(/chevrolet/malibu/vi-2003-2006/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) in Engine Electrical.
3. There is adequate fuel in the fuel tank

Engine Cranks but Does Not Run

The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit, via an internal integrated circuit, called an output driver module. When the PCM commands the relay ON, the relay coil creates an electromagnetic field. This electromagnetic field overcomes the spring tension and pulls the armature contact into the stationary contact of the relay load circuit. The closing of the relay contacts allows the current to flow from the battery to the following fuses and relays

1. ETC fuse
2. Emission fuse
3. A/C relay
4. Air pump relay, if equipped

When the ignition switch is turned to the OFF position, power is interrupted to the output driver module in the PCM and the relay electromagnetic field collapses. This action allows the spring tension pulling on the armature to separate from the relay load circuit contact, which interrupts current flow to the fuses and relays.

If the powertrain 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 powertrain relay system diagnosis table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.

Powertrain Relay Diagnosis

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 «Intermittent Conditions»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__intermittent-conditions) .

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

1. 3: This step determines if the condition is located on the coil side or the switch side of the circuit.
2. 4: This step verifies that the PCM is providing voltage to the fuel pump relay.
3. 5: This step tests for an open in the ground circuit to the fuel pump relay.
4. 6: This step determines if a voltage is constantly being applied to the fuel pump relay.
5. 13: This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.

Fuel Pump Electrical Diagnosis

System Description

The powertrain control module (PCM) enables the fuel pump relay when the ignition switch is turned ON. The PCM will disable the fuel pump relay within 2 seconds unless the PCM detects ignition reference pulses. The PCM continues to enable the fuel pump relay as long as ignition reference pulses are detected. The PCM 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 (EVAP).

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 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 contain a 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 cranking times.

Fuel System Diagnosis

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»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9) or «Fuel Injector Balance Test with Tech 2»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9) .

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 124

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 Procedure

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)

The number below refers to the step number 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 Procedure

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»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9) .
3. For an intermittent condition refer to «Intermittent Conditions»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-troubleshooting-35l-lx9__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

Description

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 emissions (EVAP) diagnostics complete one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics complete 2 test cycles.

1. Operate the vehicle under the condition of the customer's 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 pipe
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. 3: This test is to locate fuel leakage in the fuel lines.
2. 4: This step tests for fuel leaks below the fuel tank fuel level.
3. 5: This test is to locate fuel vapors escaping above the fuel level in the fuel tank.

Fuel Tank Leak Test

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 .

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

Test Procedure

1. Turn ON the J 44175 Fuel Composition Tester.
2. Verify the fuel composition tester is operational by measuring the AC frequency output with a DMM. Refer to «Measuring Frequency»(/chevrolet/malibu/vi-2003-2006/remont/body-electrical/#wiring-systems-specifications-component-views-and-connector-end-views__measuring-frequency) in Wiring Systems. A frequency without a fuel sample in the test cell indicates that the tester is working correctly.
3. Install the J 34730-1A Fuel Pressure Gage. Refer to «Fuel Pressure Gage Installation and Removal»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-introduction-22l-l61) .
4. Close the bleed valve on the fuel pressure gage.
5. Place the bleed hose (1) of the fuel pressure gage into the 100 ml beaker (2).
6. Command the fuel pump relay ON with a scan tool.
7. Slowly open the bleed valve on the fuel pressure gage, until an adequate fuel sample is obtained.
8. If water appears in the fuel sample, clean the fuel system and replace the fuel in the vehicle. Refer to «Fuel System Cleaning»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-introduction-22l-l61__fuel-system-cleaning) .
9. Pour the fuel sample from the beaker (1) into the J 44175 , until the level of the fuel is at the top of each fuel test port (2).
10. Observe the diagnostic LEDs on the fuel composition tester. If the red fuel diagnostic LED is illuminated, a fuel contamination condition exists. Refer to «Fuel System Cleaning»(/chevrolet/malibu/vi-2003-2006/remont/testing-diagnostics/#engine-control-system-introduction-22l-l61__fuel-system-cleaning) .
11. Measure the output frequency of the fuel composition tester.
12. Subtract 50 from the reading on the DMM to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the following table.
13. If the fuel sample contains more than 10 percent ethanol, replace the fuel in the vehicle.

Fuel Composition Test Examples

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

1. 4: This step tests the MAP sensor's ability 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

There are three 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 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 IC control circuit to the ICM for the proper coil to enable a spark event.

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 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 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.

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 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.

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 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.

1. The vehicle speed sensor (VSS) is between 45-112 km/h (28-20 mph).
2. The barometric pressure is more than 74 kPa.
3. The manifold absolute pressure (MAP) sensor parameter does not change more than 1.1 kPa.
4. The traction control is not active.
5. The ignition 1 voltage is between 11-18 volts.
6. The intake air temperature (IAT) is between -7 to +100°C (20-212°F).
7. The A/C Relay Command parameter does not change.
8. The Current Gear parameter does not change.
9. The engine coolant temperature (ECT) is between 75-126°C (167-258°F).
10. The engine speed is between 1,000-1,500 RPM.
11. The manifold absolute pressure (MAP) is between 17-43 kPa.
12. The engine is not running in Decel Fuel Cutoff mode.
13. The EGR position is less than 1 percent.
14. The throttle position (TP) sensor is less than one percent.
15. The vehicle speed is more than 45 km/h (28 mph) during deceleration.

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 provides an indication of when 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. 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 74 kPa.
2. The engine coolant temperature (ECT) is below 30°C (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 8°C (14°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 heated oxygen sensor/ oxygen sensor (HO2S/O2S) 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 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.

1. DTCs P0133, P0136, P0140, P0153, P0156, P0160, P1133, P1134, P1153, P1154 are not set.
2. The startup engine coolant temperature (ECT) is less than 35°C (95°F).
3. The engine is running in Closed Loop fuel control.
4. The engine has been running for more than 1 minute.
5. The battery voltage is between 9-18 volts.
6. The mass air flow (MAF) is between 15-30 grams per second.
7. The engine speed is between 1,300-3,000 RPM.
8. The throttle position (TP) sensor is more than 2 percent.
9. The vehicle speed sensor (VSS) is between 33-120 km/h (20-75 mph).
10. The short term fuel trim is between 97.5-102.5.
11. The startup intake air temperature (IAT) is less than 35°C (95°F).
12. The startup engine coolant temperature (ECT) and IAT are within 6°C (10.8°F) of each other.
13. The exhaust gas recirculation (EGR) tests are not active.
14. The catalyst test are not active.
15. The EVAP canister purge duty cycle is more than 0 percent.

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 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.

1. DTCs P0135, P0141, P0155, P0161 are not set.
2. The catalyst tests are not active.
3. The exhaust gas recirculation (EGR) tests are not active.
4. The engine coolant temperature (ECT) is more than 65°C (149°F).
5. The engine has been running longer than 100 seconds.
6. The battery voltage is between 9-18 volts.
7. The engine speed is between 600-3,000 RPM.
8. The mass air flow (MAF) is between 4-30 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

See also:
• Diagnostic System Check - Vehicle
• Scan Tool Data List
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Engine Controls Schematics
• Charging System Test
• Power Distribution Schematics
• Service Programming System (SPS)
• Temperature vs Resistance
• Spark Plug Inspection
• Spark Plug Wire Inspection
• Oil Consumption Diagnosis
• Engine Compression Test
• Camshaft and Bearings Cleaning and Inspection
• Cylinder Head Cleaning and Inspection
• Piston, Connecting Rod and Bearings Cleaning and Inspection
• Crankshaft and Bearings Cleaning and Inspection
• Restricted Exhaust
• Silicon Contamination of Heated Oxygen Sensors Notice
• Heated Oxygen and Oxygen Sensor Notice
• Scan Tool Data Definitions
• Air Cleaner Element Replacement
• Exhaust Leakage
• DTC P0300
• Ignition System Specifications
• Loss of Coolant
• Thermostat Diagnosis
• Cooling Fan Inoperative (LX9)
• Cooling Fan Inoperative (L61)
• Drive Belt Tensioner Diagnosis
• Symptoms - Engine Mechanical
• Torque Converter Diagnosis Procedure
• Valve Rocker Arm and Push Rods Cleaning and Inspection
• Symptoms - Instrument Panel, Gages and Console
• Symptoms - Hydraulic Brakes
• Engine Mount Inspection
• Instrument Cluster Schematics
• Instrument Panel, Gages and Console Component Views
• Instrument Panel, Gages and Console Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Circuit Testing
• Wiring Repairs
• Diagnostic Trouble Code (DTC) List - Vehicle
• Battery Inspection/Test
• Engine Cranks Slowly
• Engine Controls Connector End Views
• Test Probe Notice
• Symptoms - Engine Electrical
• Troubleshooting with a Digital Multimeter
• Fuel Pressure Relief Procedure
• Testing for Continuity
• Intake Manifold Removal - Upper
• Fuel Injector Cleaning Procedure
• Probing Electrical Connectors
• Lifting and Jacking the Vehicle
• Scan Tool Output Controls
• Fuel System Cleaning
• Measuring Frequency
• Altitude vs Barometric Pressure
• Road Test Caution
• DTC P1404
• DTC P0135 or P0155
• 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
• Symptoms - Engine Controls
• Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)
• Intermittent Conditions
• Inspection/Maintenance (I/M) System DTC Table