Engine Control System & Fuel System - 4.3l - Troubleshooting & Diagnosis Chevrolet Chevy Express H1500

Important Preliminary Inspections Before Beginning

Perform Diagnostic Trouble Code (DTC) List - Vehicle 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/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-1-of-2__scan-tool-data-list) .
4. Verify the customer concern and locate the correct symptom. Inspect the items indicated under that symptom.
5. Several of the symptom procedures ask for a careful visual 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.
6. Inspect for improper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. If you can not locate an intermittent condition, a cellular phone communication signal may cause the condition.
7. If the intermittent condition exists as a start and then stall, test for DTCs relating to the vehicle theft deterrent system.

Use the following tables when diagnosing a symptom complaint

1. «Hard Start»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__hard-start)
2. «Surges/Chuggles»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__surgeschuggles)
3. «Lack of Power, Sluggishness, or Sponginess»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__lack-of-power-sluggishness-or-sponginess)
4. «Detonation/Spark Knock»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__detonationspark-knock)
5. «Hesitation, Sag, Stumble»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__hesitation-sag-stumble)
6. «Cuts Out, Misses»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__cuts-out-misses)
7. «Poor Fuel Economy»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__poor-fuel-economy)
8. «Poor Fuel Fill Quality»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__poor-fuel-fill-quality)
9. «Rough, Unstable, or Incorrect Idle and Stalling»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__rough-unstable-or-incorrect-idle-and)
10. «Dieseling, Run-On»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__dieseling-run-on)
11. «Backfire»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__backfire)

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

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. 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 the 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 the 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 condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections .

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 prevents an engine from starting. 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 (Non-HP2)»(/chevrolet/chevy-express-h1500/2003-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
2. The cranking speed is acceptable. Refer to «Engine Cranks Slowly»(/chevrolet/chevy-express-h1500/2003-2012/remont/charging-system/#battery-charging-system-and-starting-system__engine-cranks-slowly) .
3. There is adequate fuel in the fuel tank.

Engine Cranks but Does Not Run

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

Fuel Pump Electrical Circuit Diagnosis

System Description

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

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

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

Fuel System Diagnosis

The control module enables the appropriate fuel injector pulse 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 too 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 to isolate the fuel injector that is causing the condition.
2. Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
3. Perform the fuel injector coil test within the conditions of the customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.

Fuel Injector Solenoid Coil Test

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 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.

Fuel Injector Balance Test with Special Tool

The scan tool is first used to energize the fuel pump relay. The scan tool 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 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.

Fuel Injector Balance Test with Tech 2

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.

Alcohol in Fuel Testing Procedure

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

1. Using a 100 ml (3.38 oz) specified cylinder with 1 ml (0.034 oz) graduation marks, fill the cylinder with fuel to the 90 ml (3.04 oz) mark.
2. Add 10 ml (0.34 oz) of water in order to bring the total fluid volume to 100 ml (3.38 oz) and install a stopper.
3. Shake the cylinder vigorously for 10-15 seconds.
4. Carefully loosen the stopper in order to release the pressure.
5. Re-install the stopper and shake the cylinder vigorously again for 10-15 seconds.
6. Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer, which would now contain both alcohol and water, will be more than 10 ml (0.34 oz). For example, if the volume of the lower layer is increased to 15 ml (0.51 oz), this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because this procedure does not extract all of the alcohol from the fuel.

Particulate Contaminants in Fuel Testing Procedure

The fuel sample should be drawn from the bottom of the tank so that any 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 (0.53 qt) of fuel.
2. Place the container 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.
3. Observe the fuel sample. If any physical contaminants or water are present, clean the fuel system. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-2-of-2__fuel-system-cleaning) .

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

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

Test Procedure

1. Test the fuel composition using J 44175 Fuel Composition Tester and J44175-3 Instruction Manual. See «Special Tools»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-2-of-2__special-tools) .
2. If water appears in the fuel sample, perform the following steps: Clean the fuel system. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-2-of-2__fuel-system-cleaning) . Replace the fuel filter. Refer to «Fuel Tank Fuel Pump Module Replacement»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-2-of-2) .
3. Subtract 50 from the reading on the DMM in order to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the Fuel Composition Test Examples table.
4. If the fuel sample contains more than 15 percent ethanol, add fresh, regular gasoline to the vehicle's fuel tank.
5. Test the fuel composition.
6. If testing shows the ethanol percentage is still more than 15 percent, replace the fuel in the vehicle. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-2-of-2__fuel-system-cleaning) .

Fuel Composition Test Examples

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 condition that can not be overcome by the IAC valve. Refer to «Symptoms - Engine Controls»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis) .
12. If the condition is determined to be intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor) .

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

This system includes the crankshaft position (CKP) sensor, the camshaft position (CMP) sensor, the ignition coil with the ignition control module (ICM), the secondary wires, the spark plugs, and the circuit conductors and connectors.

The powertrain control module (PCM) controls the ignition system. The PCM monitors the input signals from various engine sensors. The PCM controls the dwell of the ignition primary coil, computes the desired spark timing and firing of the ignition system via an ignition control (IC) timing control circuit to the ignition control module.

The distributor ignition (DI) system diagnostic table assumes the following conditions

1. The battery is fully charged.
2. There is adequate fuel in the fuel tank.
3. The fuel delivery system is functional.

Engine mechanical conditions may prevent the distributor from rotating. Inspect the following conditions if the distributor rotor does not rotate

1. A broken distributor drive shaft
2. A worn or broken distributor drive gear
3. A worn or broken camshaft timing chain and gears

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Refer to Testing for Intermittent Conditions and Poor Connections . If a repair is necessary, refer to Wiring Repairs .

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

1. 3: This step tests for a CKP signal to the PCM.
2. 4: This step tests for an internally shorted CMP sensor.
3. 9: This step tests for spark output at more than one spark plug wire. The J 26792 Spark Plug Tester requires a minimum of 25,000 volts to operate. See «Special Tools»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-introduction-2-of-2__special-tools) .
4. 10: This step determines if spark is being delivered to the distributor cap.
5. 20: This step tests if the PCM is providing a timing control signal to the ICM.
6. 21: This step tests for a basic engine mechanical condition.

Distributor Ignition (DI) System Diagnosis

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

Conditions for Updating the I/M System Status

Each system monitor requires at least one, and sometimes several diagnostic tests. The result of each test is reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs 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 4 heated oxygen sensors, either all 4 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

Diagnostic Fault Information

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 drive cycles for those particular diagnostics. When all I/M monitored diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform the I/M Complete System Set Procedure if any I/M System Status indicators are set to NO.

I/M Data List

To determine if the I/M readiness diagnostic tests can be run this ignition cycle, use a scan tool to observe the I/M monitor enabled parameters in the I/M Data List.

Conditions for Meeting a Cold Start

1. The ignition voltage between 11-18 volts.
2. The barometric pressure (BARO) is more than 75 kPa.
3. The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
4. The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
5. The difference between the IAT and the ECT is 6°C (10.8°F)
6. The ambient air temperature is between 4-30°C (39-86°F).
7. Fuel level is between 15-85 percent

Circuit/System Verification

Review the I/M Status indicators with a scan tool. All I/M System Status indicators should report YES.

Inspection/Maintenance (I/M) System Set Procedure

1. Ensure that the vehicle meets the conditions for a cold start listed above. If the evaporative emission (EVAP) I/M System Status indicator displays NO, perform the EVAP Service bay test if available. If the EVAP Service bay test is NOT available, it may take up to 6 drive cycles, with up to 17 hours between drive cycles, for the EVAP I/M System Status indicator to transition to YES. If the O2S Heater System Status indicator displays NO, ensure that the ignition has been turned OFF for at least 10 hours.
2. Set the vehicle parking brake and ensure the vehicle is in park for automatic transmission or neutral for manual transmission.
3. Turn OFF all accessories; HVAC system, other electrical loads, including aftermarket/add-on equipment, etc.
4. Start and idle the engine for at least 2 minutes and until 65°C (149°F) is achieved.
5. Run the engine for 6.5 minutes within the following conditions: MAF parameter between 4-30 g/s Engine speed steady between 1000-3000 RPM
6. Return the engine to idle for 1 minute.
7. Apply and hold brake pedal, and shift to Drive for automatic, or apply clutch pedal for manual and operate the vehicle within the following conditions for 2 minutes: Depress the accelerator pedal until throttle position (TP) sensor angle is more than 2 percent. Mass air flow (MAF) signal between 15-30 g/s RPM steady between 1200-2000 RPM
8. Release the accelerator pedal and shift the vehicle to Park for automatic, or Neutral and release clutch pedal for manual, and allow the engine to idle for 2 minutes.
9. Quickly depress the accelerator pedal until TP Sensor Angle is more than 8 percent and return to idle, repeat 3 times.
10. Allow engine to idle for at least 2 minutes.
11. Release the parking brake and drive vehicle at 24 km/h (15 mph) or slower for 2 minutes.
12. Continue to drive the vehicle for at least 5.5 miles between 45-112 km/h (28-70 mph) with the vehicle reaching at least 80 km/h (50 mph).
13. Release the accelerator pedal for at least 2 seconds. This will allow the vehicle to enter decel fuel cut-off.
14. Depress the accelerator pedal until the TP Sensor angle is increased 3-20 percent and maintain a safe speed for 1 minute.
15. Safely stop the vehicle, with the engine in drive for automatic or in neutral with the clutch pedal depressed and parking brake applied for manual, idle for 2 minutes.
16. Shift to Park for automatic and apply the parking brake, or neutral and release clutch pedal for manual.
17. Turn OFF the ignition and exit the vehicle. Do NOT disturb the vehicle for 60 minutes.
18. Observe the Inspection/Maintenance (I/M) System Status with a scan tool. All of the I/M System Status indicators should display YES. If the EVAP I/M System Status indicator displays NO, turn OFF the ignition for 17 hours, ensure that the vehicle meets the conditions for a cold start, and repeat steps 12-18 six more times, or until the EVAP I/M System Status indicator transitions to YES. If the indicator continues to display NO, refer to the «Inspection/Maintenance (I/M) System DTC Table»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__inspectionmaintenance-im-system-dtc-table) to identify the DTCs that did not run. Follow the Conditions for Running the DTC in order to set the EVAP I/M System Status indicator

1. If any of the I/M System Status indicators display NO, refer to the «Inspection/Maintenance (I/M) System DTC Table»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-43l-troubleshooting-diagnosis__inspectionmaintenance-im-system-dtc-table) for the indicator which did not display YES. The I/M System DTC Table identifies the DTCs associated with each I/M System Status Indicator. Follow the Conditions for Running the DTC in order to set the associated status indicator.

Inspection/Maintenance (I/M) System DTC Table

Inspection/Maintenance (I/M) System DTC Table

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The purpose of the evaporative emission (EVAP) Service Bay Test is to aid in resetting the EVAP inspection/maintenance (I/M) system status. For this vehicle that is equipped with the engine off natural vacuum (EONV) diagnostic, the Service Bay Test uses the scan tool to initiate the control module's regular sequence of EVAP system DTC tests, but with different enable criteria. By using the Service Bay Test the I/M indicator can be set without the need for multiple cold soaks.

The scan tool displays for the Service Bay Test are based on the events that occur within the following three categories

1. The engine running portion of the tests-The vehicle must remain at rest, in Park, or in Neutral, during this portion of the test. This test inspects for large leaks, a leaking purge valve and/or vent system restrictions. The scan tool will display test progress or the reason for an abort or failure.
2. Drive cycle-The scan tool will display time and distance needed to warm the fuel.
3. Ignition OFF-During this portion of the test, the engine controller will remain active for up to 45 minutes when the ignition is turned OFF to allow control of the EVAP vent valve and run the EONV test. The engine controller inspects for small leaks during this period by monitoring fuel tank pressure or vacuum. If the system is sealed, there will be a pressure or vacuum change. Pressure or vacuum changes that are less than the calibrated values indicate a leak.

When the EVAP diagnostics are initiated by the Service Bay Test, the scan tool will indicate if the enable conditions listed below are not met, or will display a specific reason if the test aborts. When complete, the display will indicate that the tests passed or failed.

Conditions for Running the Test

The following conditions must be met in order to enable the Service Bay Test

1. The battery voltage is between 11-18 volts.
2. The engine coolant temperature (ECT) is less than 70°C (158°F) at start-up.
3. The EVAP I/M system status indicator is set to NO.
4. The fuel level is 15-85 percent capacity and cannot be refueled during the tests.
5. There are no DTCs displayed.
6. The vehicle must be driven for the time and distance specified on the scan tool.
7. The ambient air temperature is between 0-40°C (32-104°F)
8. The ignition must remain OFF during the engine OFF portion of the test, and the vehicle must remain at rest.

1. Install a scan tool.
2. Select the Service Bay Test with the scan tool.
3. Follow the instructions on the scan tool. If the test aborts, correct the condition for running the test and then retest. If the test fails, repair the vehicle for the condition indicated by the failure message on the scan tool.
4. Verify that the EVAP I/M system status is set to YES.

See also:
• Diagnostic Trouble Code (DTC) List - Vehicle
• Scan Tool Data List
• Power and Grounding Component Views
• Engine Controls Schematics
• Temperature Versus Resistance
• DTC P0121
• Ignition System Specifications
• Spark Plug Inspection
• Special Tools
• Distributor 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
• Exhaust Leakage
• DTC P0300
• Torque Converter Diagnosis
• Loss of Coolant
• Thermostat Diagnosis
• Drive Belt Tensioner Diagnosis
• Scan Tool Data Definitions
• Brakes Drag
• Engine Mount Inspection
• Instrument Cluster Schematics
• Diagnostic System Check - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Control Module References
• Battery Inspection/Test (Non-HP2)
• Engine Cranks Slowly
• Probing Electrical Connectors
• Fuel Pressure Relief (With CH 48027)
• Fuel Pressure Relief (Without CH 48027)
• Engine Cover Replacement
• Testing for Continuity
• Fuel Injector Cleaning
• Fuel System Cleaning
• Circuit Protection - Fuses
• Measuring Voltage
• Road Test Caution
• DTC P1133 or P1153
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• 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
• Inspection/Maintenance (I/M) System DTC Table