Engine Control System & Fuel System - 4.8l, 5.3l, and 6.0l - Troubleshooting & Diagnosis Chevrolet Chevy Express H1500

Important Preliminary Inspections Before Starting

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

1. The powertrain control module (PCM) 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/door-locks-anti-theft-systems/#immobilizer-system__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 PCM 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. The arrows on the plastic portion of the sensor must point toward the engine.
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 . 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 .

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 Techline 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 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 PCM grounds are loose or dirty. Refer to «Engine Controls Schematics»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-introduction-2-of-2) .
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 PCM 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. «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)
2. «Hard Start»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__hard-start)
3. «Surges/Chuggles»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__surgeschuggles)
4. «Lack of Power, Sluggishness, or Sponginess»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__lack-of-power-sluggishness-or-sponginess)
5. «Detonation/Spark Knock»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__detonationspark-knock)
6. «Hesitation, Sag, Stumble»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__hesitation-sag-stumble)
7. «Cuts Out, Misses»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__cuts-out-misses)
8. «Poor Fuel Economy»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__poor-fuel-economy)
9. «Poor Fuel Fill Quality»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__poor-fuel-fill-quality)
10. «Rough, Unstable, or Incorrect Idle and Stalling»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__rough-unstable-or-incorrect-idle-and)
11. «Dieseling, Run-On»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__dieseling-run-on)
12. «Backfire»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis__backfire)

Symptoms - Fuel System

Fuel System

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 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 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 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 two 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 two seconds if ignition reference pulses cease to be detected and the ignition remains ON.

A fuel pump prime terminal is located at the underhood bussed electrical center (UBEC). Refer to the UBEC cover for terminal location.

The following conditions may have caused the fuel pump fuse to open

1. A faulty fuse
2. An intermittent short in the fuel pump power supply circuit
3. An intermittent internal component failure

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

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 on the switch side of the fuel pump relay.
2. 4: This step verifies that the powertrain control module (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.

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 two 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 two 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. The use of Dielectric compound GM P/N 12377900 (Canadian P/N 10953529) in the fuel injector electrical connector may eliminate a corrosion condition.
2. Monitoring the misfire current counters, or misfire graph, may help isolate the fuel injector that is causing the condition.
3. Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
4. 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.
5. 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/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis) or «Fuel Injector Balance Test with Tech 2»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-troubleshooting-diagnosis) .

Fuel Injector Solenoid Coil Test

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

Scheme 312

Fuel Injector Balance Test Example (Typical)

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

1. 6: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the illustration above.

Fuel Injector Balance Test with Special Tool

The scan tool is first used to energize the fuel pump. 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 the flow through each injector.

Fuel Injector Balance Test Example (Typical)

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

1. 5: If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.

Fuel Injector Balance Test with Tech 2

The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected when the evaporative emission (EVAP) diagnostics complete one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics have failed 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. Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.
3. If the fuel level is low, a leak may not be evident.

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

1. 4: This step tests for fuel leaks below the fuel tank fuel level.
2. 5: This step tests for 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.

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. 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 percentage of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions such as hesitation, lack or power, stalling, or no start.

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 .

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 in non-blended gasoline, or greater than 85 percent with E85 blended gasoline for flexible fuel applications, can cause driveability conditions and may contribute to fuel system deterioration. Excessive ethanol concentrations can result in driveability conditions such as hesitation, lack of power, stalling, or a no start, and may contribute to fuel system corrosion, deterioration of fuel system components, and a restricted fuel filter.

Test Procedure

1. Test the fuel composition using J 44175 Fuel Composition Tester and J 44175-3 Instruction Manual.
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-48l-53l-and-60l-introduction-2-of-2) . Replace the fuel filter if the vehicle is equipped with a serviceable fuel filter.
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 non-blended gasoline fuel sample measures more than 15 percent ethanol, or if the E85 blended gasoline fuel sample measures more than 91 percent ethanol, add fresh, regular gasoline to the vehicle's fuel tank.
5. Test the fuel composition.
6. If additional testing indicates that the ethanol percentage is still more above 15 percent for a non-blended gasoline sample, drain and replace the vehicle's fuel. Refer to «Fuel System Cleaning»(/chevrolet/chevy-express-h1500/2003-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-48l-53l-and-60l-introduction-2-of-2) . If additional testing indicates that the E85 blended gasoline sample still measures above 91 percent, continue adding fresh, regular gasoline until the ethanol content measures 91 percent or less.

Fuel Composition Test Examples

The electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module (PCM) controls the ignition operation through 8 individual ignition control (IC) circuits. Each bank of four ignition coils is connected to the PCM, power, and ground by the following circuits

1. The low reference
2. The ground
3. The Ignition 1 voltage
4. The appropriate IC circuit

The PCM triggers an ignition coil by grounding the appropriate IC control using information from the crankshaft position (CKP) and camshaft position (CMP) sensors.

1. The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a cylinder is on either the firing or exhaust stroke by the 24X signal.
2. Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
3. For an intermittent condition, 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 number below refers to the step number on the diagnostic table.

1. 4: Monitoring the misfire current counters determines if a fault is present.

Electronic Ignition (EI) 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 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

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) provided an overview of each diagnostic category.

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 System 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 1,000-3,000 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 TP Sensor angle is more than 2 percent. Mass air flow (MAF) signal between 15-30 g/s RPM steady between 1,200-2,000 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 45 minutes.
18. Observe the 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-48l-53l-and-60l-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-48l-53l-and-60l-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

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 System Check - Vehicle
• Scan Tool Data List
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Engine Controls Schematics
• Evaporative Emissions Hose Routing Diagram
• Power and Grounding Component Views
• Temperature Versus Resistance
• Circuit Testing
• Spark Plug Inspection
• Spark Plug Wire Inspection
• Oil Consumption Diagnosis
• Engine Compression Test
• Cylinder Head Cleaning and Inspection
• Camshaft and Bearings Cleaning and Inspection
• Piston, Connecting Rod, and Bearings Cleaning and Inspection
• Crankshaft and Bearings Cleaning and Inspection
• Heated Oxygen and Oxygen Sensor Notice
• Exhaust Leakage
• DTC P0300
• Engine Overheating
• Diagnostic Starting Point - Automatic Transmission
• Restricted Exhaust
• Loss of Coolant
• Fan Clutch Diagnosis
• Symptoms - Engine Mechanical
• Wiring Repairs
• Crankcase Ventilation System Inspection/Diagnosis
• Park/Neutral Position Switch Adjustment
• Brakes Drag
• Engine Mount Inspection
• Instrument Cluster Schematics
• Control Module References
• Diagnostic Trouble Code (DTC) List - Vehicle
• Battery Inspection/Test (Non-HP2)
• Engine Cranks Slowly
• Fuel System Diagnosis
• DTC P0106 (With Throttle Actuator Control)
• Probing Electrical Connectors
• Fuel Pressure Relief (With CH 48027)
• Fuel Pressure Relief (Without CH 48027)
• Testing for Continuity
• Special Tools
• Fuel Injector Cleaning
• Fuel Injector Balance Test Notice
• Lifting and Jacking the Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Road Test Caution
• DTC P0454
• DTC P2A01 or P2A04
• 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
• Fuel Pump Electrical Circuit Diagnosis
• Inspection/Maintenance (I/M) System DTC Table