Engine Control System & Component Tests - 4.3l Chevrolet Chevy Express H2500

INTRODUCTION

Before testing separate components or systems, follow proper workflow. See DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article. If no DTCs are present and a driveability condition exists, proceed to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

COMPONENT LOCATIONS

Note. For component locations refer to COMPONENT LOCATIONS table or illustrations. (Scheme 9)- (Scheme 14).

COMPONENT LOCATIONS

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

COMPUTERIZED ENGINE CONTROLS

Note. For component locations, see COMPONENT LOCATIONS .

POWERTRAIN CONTROL MODULE

Note. To identify circuits referenced in the following ground and power tests, see WIRING DIAGRAMS or (Scheme 15)- (Scheme 18).

Ground Circuits

Check PCM connectors for corroded or loose connections. Repair as necessary. Disconnect PCM connectors. Using a DVOM, measure resistance between negative battery terminal and ground terminals at PCM harness connector. If resistance is more than 5 ohms, repair open in affected ground circuit. If resistance is 5 ohms or less, ground circuits are okay.

Power Circuits

1. Check PCM connectors for corroded or loose connections. Repair as necessary. Disconnect PCM connectors. Using a DVOM, check for battery voltage between chassis ground and continuous power terminal(s) at PCM harness connector(s). If battery voltage is present, go to next step. If battery voltage is not present, check for open fuse or fusible link. If fuse or fusible link is okay, check for open in wire between PCM terminal and power source.
2. Turn ignition switch to RUN position. Using DVOM, check for battery voltage between chassis ground and ignition power terminals at PCM harness connector(s). If battery voltage is present, power circuits are okay. If battery voltage is not present, check IGN fuse. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM terminal. If wiring is okay, check for a defective ignition switch.

PCM Harness Resistance

Turn ignition switch to LOCK position. Disconnect PCM and appropriate component harness connectors. Check for open or short circuits between appropriate PCM harness connector terminal and appropriate component harness connector terminal. If harness is open or shorted, repair as necessary.

Scheme 15

Scheme 16

Scheme 17

Scheme 18

SENSORS & SWITCHES

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

Note. For additional sensor testing specifications, see SENSOR OPERATING RANGE CHARTS - TRUCKS article.

Manufacturer does not provide testing procedures for many individual systems and components. For sensor and switch testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

CAMSHAFT POSITION SENSOR

A malfunction in Camshaft Position (CMP) sensor can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

CRANKSHAFT POSITION SENSOR

A malfunction in Crankshaft Position (CKP) sensor can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

ENGINE COOLANT TEMPERATURE SENSOR

A malfunction in Engine Coolant Temperature (ECT) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. An out-of-calibration ECT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect ECT sensor harness connector. See COMPONENT LOCATIONS . Using DVOM, measure resistance of ECT sensor at specified temperatures. See SENSOR TEMPERATURE VS RESISTANCE table. Resistance should be high when engine is cold and drop as engine warms. With vehicle sitting overnight, IAT sensor and ECT sensor should have close to the same resistance reading. If resistance is not within specification, replace ECT sensor.

SENSOR TEMPERATURE VS RESISTANCE

FUEL TANK PRESSURE SENSOR

A malfunction in the Fuel Tank Pressure (FTP) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

HEATED OXYGEN SENSORS

A malfunction in Heated Oxygen Sensor (HO2S) circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

INTAKE AIR TEMPERATURE SENSOR

A malfunction in IAT sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. An out-of-calibration IAT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect IAT sensor harness connector. See COMPONENT LOCATIONS . Using DVOM, measure resistance of IAT sensor at specified temperatures. See SENSOR TEMPERATURE VS RESISTANCE table. Resistance should be high when air temperature is cold and drop as air temperature warms. With vehicle sitting overnight, ECT sensor and IAT sensor should have close to the same resistance reading. If resistance is not within specification, replace IAT sensor.

KNOCK SENSOR

A malfunction in Knock Sensor (KS) circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

MANIFOLD ABSOLUTE PRESSURE SENSOR

A malfunction in Manifold Absolute Pressure (MAP) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

THROTTLE POSITION SENSOR

Note. Throttle Position (TP) sensor is not adjustable. Replace TP sensor as necessary.

A malfunction in TP sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

TRANSMISSION RANGE SWITCH

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

VEHICLE SPEED SENSOR

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

MODULES, MOTORS, RELAYS & SOLENOIDS

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

Note. Manufacturer does not provide testing procedures for many individual systems and components. For module, motor, relay and solenoid testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

A/C COMPRESSOR CLUTCH RELAY

See appropriate AUTOMATIC A/C-HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.

FUEL PUMP RELAY

See FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS .

TORQUE CONVERTER CLUTCH SOLENOID

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

ALCOHOL/CONTAMINANTS IN FUEL DIAGNOSIS WITH SPECIAL TOOL

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

Description

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 more in the 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 of power, stalling, or no start.

Diagnostic Procedures

1. Turn on the Fuel Composition Tester (J-44175).
2. Verify the fuel composition tester is operational by measuring the AC frequency output with a DVOM. A frequency without a fuel sample in the test cell indicates that the tester is working correctly.
3. Install fuel pressure gauge.
4. Close bleed valve on fuel pressure gauge.
5. Place the bleed hose of the fuel pressure gauge into the 100 ml beaker.
6. Using scan tool, command fuel pump relay on.
7. Slowly open the bleed valve on the fuel pressure gauge, 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.
9. Pour fuel sample from the beaker into the tester until the level of the fuel is at the top of each fuel test port.
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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-system-cleaning) .
11. Measure the output frequency of the fuel composition tester.
12. Subtract 50 from the reading on the DVOM to obtain the percentage of alcohol in the fuel sample.
13. If fuel sample contains more than 10 percent ethanol, add gasoline to the fuel tank or replace the fuel in the vehicle.

ALCOHOL/CONTAMINANTS IN FUEL DIAGNOSIS WITHOUT SPECIAL TOOL

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

Test Description

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 fuel system is contaminated with water, inspect fuel system components for rust or deterioration.

Alcohol concentrations of 10 percent or more in the 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 of 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 procedures to test the fuel quality.

1. Using a 3.38 oz. (100 ml) graduated cylinder with 0.034 oz. (1 ml) graduation marks, fill the cylinder with fuel to the 3.04 oz. (90 ml) mark.
2. Add 0.34 oz. (10 ml) of water in order to bring the total fluid volume to 3.38 oz. (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 0.34 oz. (10 ml). For example, if the volume of the lower layer is increased to 0.51 oz. (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 0.53 qt. (0.5 liter) of fuel.
2. Place 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 fuel sample. If any physical contaminants or water are present, clean fuel system. Refer to «FUEL SYSTEM CLEANING»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-system-cleaning) .

FUEL INJECTOR BALANCE TEST WITHOUT SPECIAL TOOL

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

System Description

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.

The number below refers to step number in diagnostic procedure.

1. 3 - Engine Coolant Temperature (ECT) must be below operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.

Scheme 19

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Perform «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-injector-coil-test). After performing Fuel Injector Coil Test, go to next step.
3. Observe ECT parameter with scan tool. Does scan tool indicate ECT parameter is less than 201°F (94°C)? If yes, go to next step. If no, allow engine to cool before proceeding.
4. Turn ignition off. Turn OFF all accessories. Install fuel pressure gauge. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Observe fuel pressure gauge, with fuel pump commanded ON. Is fuel pressure within 48-54 psi (334-375 kPa)? If yes, go to next step. If no, go to «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article.
5. Monitor fuel pressure gauge for one minute. Does fuel pressure decrease by more than 5 psi (34 kPa)? If yes, go to «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article. If no, go to next step.
6. Disconnect multi-way harness connector of fuel injectors. Connect Fuel Injector Tester (J-39021) to ignition 1 voltage circuit terminal and appropriate fuel injector control circuit terminal using Connector Test Adapter Kit (J-35616-A). Set amperage supply selector switch on fuel injector tester to Balance Test.5-2.5-amp position. Command fuel pump ON and then OFF with scan tool. Record fuel pressure indicated by fuel pressure gauge after fuel pressure stabilizes. This is first pressure reading. Energize fuel injector by depressing "Push to Start Test" button on fuel injector tester. Record fuel pressure indicated by fuel pressure gauge after fuel injector has stopped pulsing. This is second pressure reading. Repeat this step for each fuel injector. Subtract second pressure reading from first pressure reading for one fuel injector. Result is pressure drop value. (Scheme 19) Obtain a pressure drop value for each fuel injector. Add all individual pressure drop values. This is total pressure drop. Divide total pressure drop by number of fuel injectors. This is average pressure drop. Does any fuel injector have a pressure drop value more than average pressure drop or less than average pressure drop by 1.5 psi (10 kPa)? If yes, go to next step. If no, go to «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-43l__symptoms) in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article.
7. Replace affected fuel injectors. After repairs, go to next step.
8. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-43l__symptoms) in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article.

FUEL INJECTOR BALANCE TEST WITH TECH 2

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

Scan tool first energizes fuel pump and then injectors for a precise amount of time allowing a measured amount of fuel into manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.

The numbers below refer to step numbers in diagnostic procedure.

1. 3 - Engine Coolant Temperature (ECT) must be below operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Perform «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-injector-coil-test) . After performing Fuel Injector Coil Test, go to next step.
3. Observe ECT parameter with scan tool. Does scan tool indicate ECT parameter is less than 201°F (94°C)? If yes, go to next step. If no, allow engine to cool before proceeding.
4. Turn ignition off. Turn OFF all accessories. Install fuel pressure gauge. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Observe fuel pressure gauge, with fuel pump commanded ON. Is fuel pressure within 48-54 psi (334-375 kPa)? If yes, go to next step. If no, go to «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article.
5. Monitor fuel pressure gauge for one minute. Does fuel pressure decrease by more than 5 psi (34 kPa)? If yes, go to «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article. If no, go to next step.
6. With scan tool, select Fuel Injector Balance Test function, within Special Functions menu. Select an injector to be tested. Press ENTER. This will prime fuel system. Record fuel pressure indicated by fuel pressure gauge after fuel pressure stabilizes. This is first pressure reading. Energize fuel injector by depressing PULSE INJECTOR button on scan tool. This will energize injector and decrease fuel pressure. Record fuel pressure indicated by fuel pressure gauge after fuel injector has stopped pulsing. This is second pressure reading. Press ENTER again to bring you back to Select Injector screen. Repeat this step for each fuel injector. Subtract second pressure reading from first pressure reading for one fuel injector. Result is pressure drop value. Obtain a pressure drop value for each fuel injector. Add all individual pressure drop values. This is total pressure drop. Divide total pressure drop by number of fuel injectors. This is average pressure drop. Does any fuel injector have a pressure drop value that is more than average pressure drop or less than average pressure drop by 1.5 psi (10 kPa)? If yes, go to next step. If no, go to «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-43l__symptoms) in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article.
7. Replace affected fuel injectors. After repairs, go to next step.
8. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-43l__symptoms) in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article.

FUEL INJECTOR CIRCUIT DIAGNOSIS

A malfunction in the fuel injection circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

FUEL INJECTOR COIL TEST

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

Circuit Description

Control module enables appropriate fuel injector on intake stroke for each cylinder. A voltage is supplied directly to fuel injectors. Control module controls each fuel injector by grounding 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. Fuel injector coil windings are affected by temperature. Resistance of fuel injector coil windings will increase as temperature of fuel injector increases.

Diagnostic Aids

1. Monitoring misfire current counters or misfire graph, may help isolate fuel injector that is causing condition.
2. Operating vehicle over a wide temperature range may help isolate fuel injector that is causing condition.
3. Perform fuel injector coil test within conditions of customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Observe Engine Coolant Temperature (ECT) parameter with scan tool. Is ECT value within 50-90°F (10-32°C)? If yes, go to next step. If no, go to step 4 .
3. Disconnect the multi-way harness connector of the fuel injectors. Using a DVOM, measure resistance of each fuel injector between the ignition 1 circuit and the fuel injector control circuit, at the multi-way connector. Is resistance within the 11-14 ohms for each injector? If yes, go to «FUEL INJECTOR BALANCE TEST WITHOUT SPECIAL TOOL»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-injector-balance-test-without-special) or «FUEL INJECTOR BALANCE TEST WITH TECH 2»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-injector-balance-test-with-tech) . If no, go to step 6 .
4. Disconnect the multi-way harness connector of the fuel injectors. Using DVOM, measure the resistance of each fuel injector between the ignition 1 voltage circuit and the fuel injector control circuit, at the multi-way connector. Record each fuel injector resistance value. Subtract the lowest resistance value from the highest resistance value. Is difference equal to or less than 3 ohms? If yes, go to «FUEL INJECTOR BALANCE TEST WITHOUT SPECIAL TOOL»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-injector-balance-test-without-special) or «FUEL INJECTOR BALANCE TEST WITH TECH 2»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l__fuel-injector-balance-test-with-tech) . If no, go to next step.
5. Add all fuel injector resistance values to obtain a total resistance value. Divide total resistance value by number of fuel injectors to obtain an average resistance value. Subtract lowest and highest individual fuel injector resistance values from average resistance value. Replace fuel injector that displays greatest resistance difference, more or less than average. After repairs, go to step 7 .
6. Replace fuel injector(s) that are outside of 11-14 ohms range. After repairs, go to next step.
7. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to step 2 .

Scheme 20

Scheme 21

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

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) under SELF DIAGNOSTIC SYSTEM in SELF DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. After performing diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, command fuel pump relay on and off. Repeat commands as necessary. Does fuel pump turn on and off? If yes, problem is intermittent. If no, go to next step.
3. Using scan tool, command fuel pump relay on and off. Fuel pump relay is located in underhood fuse/relay block. (Scheme 20) Do you hear a click when you command fuel pump relay on and off? If yes, go to step 9. If no, go to next step.
4. Turn ignition off. Remove fuel pump relay. Turn ignition on, with engine off. Probe control circuit of fuel pump relay with a test light that is connected to a good ground. (Scheme 21) Command fuel pump relay ON and OFF with a scan tool. Does test light turn ON and OFF? If yes, go to next step. If no, go to step 6.
5. Connect a test light between control circuit of fuel pump relay and ground circuit of fuel pump relay. Command fuel pump relay on and off with a scan tool. Does test light turn on and off? If yes, go to step 19. If no, go to step 22.
6. Does test light remain illuminated with each command? If yes, go to next step. If no, go to step 8.
7. Test control circuit of fuel pump relay for a short to voltage. (Scheme 21) Did you find and correct condition? If yes, go to step 27. If no, go to step 26.
8. Test control circuit of fuel pump relay for a short to ground or an open. Did you find and correct condition? If yes, go to step 27. If no, go to step 20.
9. Turn ignition on, with engine off. Does fuel pump operate continuously? If yes, go to next step. If no, go to step 11.
10. Turn ignition off. Remove fuel pump relay. Turn ignition on, with engine off. Does fuel pump operate continuously? If yes, go to step 21. If no, go to step 25.
11. Inspect fuel pump fuse. Is fuse open? If yes, go to next step. If no, go to step 14.
12. Test supply voltage circuit of fuel pump for a short to ground between fuel pump fuse and fuel pump. Replace fuel pump fuse, if necessary. Did you find and correct condition? If yes, go to step 27. If no, go to next step.
13. Connect all disconnected electrical components. Install a new fuel pump fuse. Command fuel pump relay on with a scan tool. Inspect fuel pump fuse. Is fuse open? If yes, go to step 24. If no, problem is intermittent.
14. Turn ignition off. Remove fuel pump relay. Turn ignition on, with engine off. Probe ignition 1 voltage circuit of fuel pump relay, switch side, with a test light connected to a good ground. Does test light illuminate? If yes, go to next step. If no, go to step 23.
15. Connect a 20-amp fused jumper wire between ignition 1 voltage circuit of fuel pump relay and supply voltage circuit of fuel pump. Does fuel pump operate? If yes, go to step 19. If no, go to next step.
16. Test supply voltage circuit of fuel pump for an open or high resistance between fuel pump relay and fuel pump. Did you find and correct condition? If yes, go to step 27. If no, go to next step.
17. Test ground circuit of fuel pump for an open or high resistance. Did you find and correct condition? If yes, go to step 27. If no, go to next step.
18. Test for an intermittent and for a poor connection at fuel sender cover. Did you find and correct condition? If yes, go to step 27. If no, go to step 24.
19. Test for an intermittent and for a poor connection at fuel pump relay. Did you find and correct condition? If yes, go to step 27. If no, go to step 25.
20. Test for an intermittent and for a poor connection at PCM. Did you find and correct condition? If yes, go to step 27. If no, go to step 26.
21. Repair short to voltage in supply voltage circuit of fuel pump. After repairs, go to step 27.
22. Repair open or high resistance in ground circuit of fuel pump relay. After repairs, go to step 27.
23. Repair open in ignition 1 voltage circuit of fuel pump relay. After repairs, go to step 27.
24. Inspect for poor connections at fuel pump, within fuel tank, before replacing fuel pump. Replace fuel sender. Replace fuel pump fuse, if necessary. After repairs, go to step 27.
25. Replace fuel pump. After replacing fuel pump, go to step 27.
26. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Perform PCM programing. After replacing PCM, go to next step.
27. Operate system in order to verify repair. Did you correct condition? If yes, system is okay. If no, go to step 2.

FUEL SYSTEM CLEANING

Note. When flushing the fuel tank, fuel and water mixture needs to be treated as a hazardous material. The material needs to be handled in accordance with all local, state and federal laws and regulations. Have Class "B" fire extinguisher near the work area.

Cleaning Procedures

1. Disconnect negative battery cable.
2. Relieve fuel system pressure. Refer to «FUEL SYSTEM PRESSURE RELEASE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-system-pressure-release) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article.
3. Drain fuel tank.
4. Remove fuel tank.
5. Remove fuel sender assembly.
6. Inspect fuel strainer. Replace a contaminated strainer and inspect fuel pump.
7. Inspect fuel pump inlet for dirt and debris. Replace fuel pump if you find dirt or debris in fuel pump inlet.
8. Flush fuel tank with hot water.
9. Pour water out of fuel sender assembly opening.
10. Rock the tank to be sure that removal of the water from tank is complete.
11. Inspect the in-line fuel filter for contamination.
12. Replace fuel filter, if plugged.

FUEL SYSTEM PRESSURE TEST

Note. For fuel system pressure testing, see FUEL SYSTEM PRESSURE RELEASE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article.

Fuel tank leak test is used to locate any fuel or fuel vapor escaping fuel tank area. Fuel vapors escaping above fuel level will be detected when Evaporative (EVAP) emission diagnostics complete one test cycle. Malfunction Indicator Light (MIL) will illuminate after EVAP diagnostics complete 2 test cycles.

1. Operate vehicle under condition of customer's concern. Under high temperature conditions fuel vapors may increase to point of EVAP canister vapor saturation. Fuel vapors would then be released into atmosphere. Once engine is running and EVAP purge is enabled, all fuel vapor release would be eliminated.
2. Movement of EVAP pipes or fuel pipes may help find an intermittent condition.

The numbers below refer to step numbers in diagnostic procedures.

1. 1 - Perform this procedure in order to determine that no EVAP diagnostic DTC is present.
2. 3 - This test is to locate fuel leakage in fuel lines.
3. 4 - This tests for fuel leaks below fuel tank fuel level.
4. 5 - This test is to locate fuel vapors escaping above fuel level in fuel tank.

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.
2. Raise vehicle. Inspect fuel tank and fuel pipes for damage or external leaks. Did you find fuel leaking from fuel tank? If yes, go to step 6 . If no, go to next step.
3. Turn ignition on, with engine off. Using scan tool, command fuel pump ON. Inspect for fuel leaking from fuel pipes. Did fuel leak from fuel pipes? If yes, go to step 7 . If no, go to next step.
4. Turn ignition off. Install Fuel Tank Cap Adapter (J-41415-40). Connect Evaporative Emissions System Tester (J-41413-200) to fuel tank cap adapter. Turn ignition on, with engine off. Using scan tool, seal EVAP system. DO NOT exceed 15 in. H2O. With EVAP pressure/purge diagnostic station, pressurize fuel tank. Did fuel leak from fuel tank? If yes, go to step 6 . If no, go to next step.
5. With EVAP pressure/purge diagnostic station, maintain pressure in fuel tank. With Ultrasonic Leak Detector (J-41416), test for leaks above fuel level in following locations: Fuel tank, fill limiter vent valve, pressure relief valve and rollover valves. Fuel sender housing and fuel sender seal. Fuel Tank Pressure (FTP) sensor seal. EVAP vapor pipes. Fuel fill pipe and hose. Did you locate a fuel leak? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l) .
6. Replace fuel tank. After repairs, system is okay.
7. Replace leaking fuel pipe. After repairs, system is okay.
8. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 2 .

IDLE CONTROL SYSTEM

Note. For idle control system testing, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

IDLE AIR CONTROL SYSTEM DIAGNOSIS

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS .

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 PCM. When 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 is turned off. First, 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 engine idle speed is out of range for a calibrated period of time, an idle speed DTC sets.

Inspect for the following conditions

1. High resistance in an IAC valve control circuit.
2. The correct 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 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 TP sensor.
8. Excessive deposits in the IAC passage or on IAC pintle.
9. Excessive deposits in the throttle bore or on the throttle plate.
10. Vacuum leaks.
11. A high or unstable idle condition could be caused by a non-IAC system problem that cannot be overcome by the IAC valve.
12. For intermittent conditions, see «INTERMITTENTS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-43l__intermittents) in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article.

The number below refers to step number in diagnostic procedure.

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 light should not flash while the IAC Counts are incrementing.

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Set parking brake and block drive wheels. Start engine. Turn OFF all accessories. Using scan tool in RPM Control function, slowly increment engine speed to 1700 RPM, then to 600 RPM, then to 1700 RPM. Exit the RPM Control function. Did the engine speed parameter stabilize within 100 RPM less than the commanded engine speed or within 200 RPM above the commanded RPM? If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l). If no, go to next step.
3. Turn ignition off. Disconnect the IAC valve. Connect an IAC Motor Driver (J-37027-1A) to the IAC valve. Start engine. Using IAC motor driver, command the IAC valve in until 600 RPM is reached. Command the IAC valve out until 1700 RPM is reached. Return engine speed to the desired idle speed parameter. Did engine speed parameter steadily decrease to 600 RPM and steadily increase to 1700 RPM when IAC valve was commanded in and out? If yes, go to step 5. If no, go to next step.
4. Did you observe an excessively high idle condition that could not be controlled with the IAC motor driver? If yes, go to step 11. If no, go to step 12.
5. Connect a test light between one of the IAC valve control circuits and a good ground. Start engine. Observe the IAC Counts parameter with scan tool. Using IAC Motor Driver (J-37027-1), command high RPM until the IAC Counts parameter starts to increment. Command low RPM until the IAC Counts parameter starts to increment. Return engine speed to the desired idle speed parameter. Repeat procedure for the other 3 IAC valve control circuits. Did the test light remain on, never flashing, while the IAC counts were incrementing for any of the IAC valve control circuits? If yes, go to step 10. If no, go to next step.
6. Did the test light remain off, never flashing, while the IAC counts were incrementing for any of the IAC valve control circuits? If yes, go to step 9. If no, go to next step.
7. Connect a test light between the IAC coil "A" low control circuit and IAC coil "A" high control circuit. (Scheme 22) Observe the IAC Counts parameter with a scan tool and test light. Using IAC motor driver, command high RPM until the IAC counts parameter starts to increment. Command low RPM until the IAC counts parameter starts to increment. Return the engine speed parameter to the desired idle speed parameter. Repeat procedure with test light connected between the IAC coil "B" low control circuit and IAC coil "B" high control circuit. Did the test light stay illuminated, never flashing, while the IAC counts were incrementing? If yes, go to next step. If no, go to step 17.
8. Test for an intermittent and for a poor connection at the IAC valve. Did you find and correct the condition? If yes, go to step 18. If no, go to step 13.
9. Turn ignition off. Disconnect PCM. Test the circuit where the test light remained OFF for an open circuit, short to ground, or short to another IAC valve control circuit. Did you find and correct the condition? If yes, go to step 18. If no, go to step 13.
10. Turn ignition on. Test the IAC valve control circuit where the test light remained illuminated for a short to voltage, or short to another IAC valve control circuit. Did you find and correct the condition? If yes, go to step 18. If no, go to step 13.
11. Inspect throttle body for damage and tampering, a skewed TP sensor signal, throttle lever screw for tampering (if equipped) or vacuum leaks. Inspect for faulty or incorrectly installed PCV valve and hose, if equipped. Inspect throttle shaft for binding, throttle linkage or cruise control linkage for binding, if equipped. Remove IAC valve. Inspect for debris in IAC passage, excessive deposits on throttle plate, excessive deposits in throttle bore, or excessive deposits on IAC valve pintle. Did you find and correct the condition? If yes, go to step 18. If no, go to step 15.
12. Inspect throttle body for damage and tampering, throttle lever screw for tampering (if equipped), excessive deposits on throttle plate, or restricted air intake system. Inspect for collapsed or clogged air intake duct, before and after the air filter element, a restricted air filter element, restriction at throttle body intake screen, if equipped. Remove IAC valve. Inspect for excessive deposits on the IAC valve pintle and in IAC valve passage. Did you find and correct the condition? If yes, go to step 18. If no, go to step 15.
13. Test for an intermittent and for a poor connection at PCM. Did you find and correct the condition? If yes, go to step 18. If no, go to next step.
14. Disconnect PCM. Test all IAC valve control circuits for high resistance. Did you find and correct the condition? If yes, go to step 18. If no, go to step 17.
15. Test for an intermittent and for a poor connection at the IAC valve. Did you find and correct the condition? If yes, go to step 18. If no, go to next step.
16. Replace IAC valve. After replacing IAC valve, go to step 18.
17. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Program replacement PCM. After repairs, go to next step.
18. Reconnect any disconnected components. Clear DTCs with scan tool. Turn ignition off for 30 seconds. Attempt to reproduce the original symptoms to verify the repair. Did you verify the repair? If yes, go to next step. If no, go to step 2.
19. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__diagnostic-trouble-code-definitions) in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article. If no, system is okay.

Scheme 22

IGNITION SYSTEMS

Note. For ignition system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

ELECTRONIC IGNITION SYSTEM DIAGNOSIS

See DISTRIBUTOR IGNITION SYSTEM under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA article.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For component locations, see COMPONENT LOCATIONS .

Note. For emission and sub-system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

Electric AIR Pump

For electric AIR pump testing, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

EXHAUST GAS RECIRCULATION

Note. For Exhaust Gas Recirculation (EGR) system diagnosis, see appropriate INSPECTION/MAINTENANCE PROCEDURES in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

FUEL EVAPORATION

Note. Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.

EVAP Control System Diagnosis

For EVAP control system diagnosis, see appropriate INSPECTION/MAINTENANCE PROCEDURES in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

1. Rough idle.
2. Stalling or low idle speed.
3. Oil leaks.
4. Oil in air cleaner.
5. Sludge in engine.

A leaking PCV valve or hose could cause

1. Rough idle.
2. Stalling.
3. High idle speed.

If engine idles rough, check for clogged PCV valve, or for plugged or broken PCV hoses BEFORE adjusting idle. Check PCV valve application to ensure valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Disconnect PCV valve vacuum hose from cylinder head cover. Run engine at idle. Place thumb over open end of PCV valve vacuum hose to check for vacuum. If vacuum does not exist, check for obstruction in source vacuum supply. If source vacuum supply is okay, replace PCV valve.
2. Turn ignition off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits that may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace as necessary.
4. Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

Note. For component locations, see COMPONENT LOCATIONS .

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Manufacturer does not provide testing procedures for many individual systems and components. For system and component testing not listed, perform related DTC testing procedure. See S DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L CHEVY EXPRESS & SAVANA article.

A/C COMPRESSOR CLUTCH CONTROLS

Note. For A/C compressor clutch circuit testing, see appropriate AUTOMATIC A/C-HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. See appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL for terminal and wire color identification.

TRANSMISSION

Note. For transmission electronic controls and component testing, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. For component circuit identification, see TRANSMISSION in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

CHEVY EXPRESS - G1500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

CHEVY EXPRESS - G2500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SAVANA - G1500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SAVANA - G2500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

See also:
• DIAGNOSTIC PROCEDURE
• NO-START DIAGNOSIS
• SYMPTOMS
• SENSOR OPERATING RANGE CHARTS - TRUCKS
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS
• FUEL SYSTEM DIAGNOSIS
• FUEL SYSTEM PRESSURE RELEASE
• INTERMITTENTS
• COMPONENT LOCATIONS
• COMPONENT LOCATIONS
• FUEL SYSTEM CLEANING
• FUEL INJECTOR COIL TEST
• FUEL INJECTOR BALANCE TEST WITHOUT SPECIAL TOOL
• FUEL INJECTOR BALANCE TEST WITH TECH 2