Engine Controls - System & Component Testing - 8.1l Chevrolet Avalanche I

INTRODUCTION

Note. Unless specified otherwise, Sierra and Silverado information also applies to Cab & Chassis Sierra and Cab & Chassis Silverado.

Before testing separate components or systems, follow proper workflow. See DIAGNOSTIC STARTING POINT - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If no DTCs are present and a driveability condition exists, proceed to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SILVERADO, SUBURBAN & YUKON XL 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 31)- (Scheme 40).

COMPONENT LOCATIONS

Scheme 31

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

Scheme 38

Scheme 39

Scheme 40

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 41) - (Scheme 46).

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 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

SENSORS & SWITCHES

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

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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

ACCELERATOR PEDAL POSITION SENSOR

A malfunction in Accelerator Pedal Position (APP) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

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.

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.

Diagnostic Procedures

1. Test the fuel composition using the Fuel Composition Tester (J-44175) and Instruction Manual (J-44175-3).
2. If water appears in the fuel sample, clean the fuel system. See «FUEL SYSTEM CLEANING»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-system-cleaning) and replace fuel filter.
3. Subtract 50 from the reading on the DVOM in order to obtain the percentage of alcohol in the fuel sample.
4. If 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 fuel in the vehicle. See «FUEL SYSTEM CLEANING»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-system-cleaning) .

ALCOHOL/CONTAMINANTS IN FUEL DIAGNOSIS WITHOUT SPECIAL TOOL

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

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 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 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-system-cleaning) .

FUEL INJECTOR BALANCE TEST WITHOUT SPECIAL TOOL

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

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 47

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Perform «FUEL INJECTOR COIL TEST»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__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 PRESSURE TEST»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-81l) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 PRESSURE TEST»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-81l) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 47) 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SILVERADO, SUBURBAN & YUKON XL 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SILVERADO, SUBURBAN & YUKON XL article.

FUEL INJECTOR BALANCE TEST WITH TECH 2

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

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. 5 If the pressure drop value for each fuel injector is within 1.5 psi (10 kPa) 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.

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Perform «FUEL INJECTOR COIL TEST»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-injector-coil-test) . After performing Fuel Injector Coil Test, go to next step.
3. Turn ignition and all accessories off. Install fuel pressure gauge. Turn ignition on, with engine off. Using scan tool, command fuel pump on. You may need to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. DO NOT start engine. Observe fuel pressure gauge, with fuel pump commanded ON. Is fuel pressure 55-62 psi (385-425 kPa)? If yes, go to next step. If no, diagnose fuel system.
4. Observe fuel pressure gauge for one minute. Does the fuel pressure drop more than 5 psi (34 kPa)? If yes, diagnose fuel system. If no, go to next step.
5. Using 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SILVERADO, SUBURBAN & YUKON XL article.
6. Replace affected fuel injectors. 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 «SYMPTOMS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SILVERADO, SUBURBAN & YUKON XL 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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

FUEL INJECTOR COIL TEST

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

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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-injector-balance-test-without-special) or «FUEL INJECTOR BALANCE TEST WITH TECH 2»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-injector-balance-test-without-special) or «FUEL INJECTOR BALANCE TEST WITH TECH 2»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__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 48

Scheme 49

When the ignition is turned on, the PCM will turn on the in-tank fuel pump. The in-tank fuel pump will remain on as long as the engine is cranking or running and PCM is receiving reference pulses. If there are no reference pulses, PCM will turn the in-tank fuel pump off 2 seconds after ignition is turned on or 2 seconds after engine stops running.

The following conditions may have caused fuel pump fuse to open: A faulty fuse, intermittent short in fuel pump power supply circuit or an intermittent internal component failure.

The numbers below refer to step numbers on diagnostic procedure.

1. 2 - Command both the ON and OFF states. Repeat the commands as necessary.
2. 3 - This step determines if condition is located on coil side or on switch side of the circuit.
3. 4 - This step verifies that PCM is providing voltage to fuel pump relay.
4. 5 - This step tests for an open in ground circuit to fuel pump relay.
5. 6 - This step determines if a voltage is constantly being applied to fuel pump relay.
6. 12 - To gain access to the fuel pump connector, the fuel tank may need to be removed.
7. 13 - This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.
8. 15 - Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.
9. 16 - To gain access to the fuel pump connector, the fuel tank may need to be removed.
10. 17 - Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under SELF DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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. See «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l). 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 48) 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 49) 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 21.
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 49) 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 19.
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. Inspect for poor connections at the fuel pump. Did you find and correct the condition? If yes, go to step 27. If no, go to step 24.
19. Test for 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. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 27. If no, go to step 26.
21. Repair the supply voltage circuit of the fuel pump for a short to voltage. After repairs, go to step 27.
22. Repair open in fuel pump relay ground circuit. After repairs, go to step 27.
23. Repair the battery voltage circuit of the fuel pump relay switch. After repairs, go to step 27.
24. Replace fuel pump. After replacing fuel pump, go to step 27.
25. Replace fuel pump relay. After replacing relay, go to step 27.
26. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram ECM. 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. Remove the fuel sending unit.
2. Inspect fuel strainer. Replace sending unit if the strainer is contaminated.
3. Inspect fuel pump inlet for dirt and debris. Replace sending unit if dirt or debris is found in fuel pump inlet.
4. Flush fuel tank with hot water.
5. Pour the water out of the sending unit opening. Rock the tank to be sure that removal of the water from the tank is complete.
6. Install the fuel sending unit.

FUEL SYSTEM PRESSURE TEST

Note. For fuel system pressure testing, see FUEL SYSTEM PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l) .
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 component locations, see COMPONENT LOCATIONS .

Note. For idle control system testing, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

IGNITION SYSTEMS

Note. For ignition system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

ELECTRONIC IGNITION SYSTEM DIAGNOSIS

See ELECTRONIC IGNITION SYSTEM under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

The ignition relay is a normally open relay. The relay armature is held in open position by spring tension. When ignition switch is turned to run or start position, current will flow through relay coil. A wire connected to other end of relay coil completes path to ground. The electromagnetic field created by relay coil, overcomes spring tension and moves armature allowing relay contacts to close. The closed relay contacts allow current to flow from battery to following fuses: PCM 1, ETC/ECM, INJ 1, INJ 2 and SBA fuse, if equipped.

When ignition switch is turned off, electromagnetic field collapses. This action allows spring tension to move armature away from relay contacts, which interrupts current flow to fuses. If ignition relay fails to close, engine will crank, but will not run. The class 2 communications will be available with use of a scan tool.

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under SELF DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. After performing diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Remove underhood fuse/relay block cover. Probe following fuses with a test light connected to a good ground: PCM 1, ETC/ECM, INJ 1, INJ 2, and SBA fuse, if equipped. (Scheme 48) Does test light illuminate on at least one test point of each fuse? If yes, go to next step. If no, go to step 10.
3. Turn ignition off. Probe both test points of PCM 1 fuse with a test light connected to a good ground. Does test light illuminate on either test point of fuse? If yes, go to next step. If no, go to step 30.
4. Turn ignition off. Remove ignition relay from underhood fuse/relay block. Probe ignition 1 voltage circuit of ignition relay at underhood fuse/relay block with a test light connected to a good ground. Does test light illuminate? If yes, go to step 7. If no, go to next step.
5. Test relay load bus bar of underhood fuse/relay block between ignition relay and fuses to circuit components for a short to battery positive voltage. Did you find a condition? If yes, go to step 29. If no, go to next step.
6. Turn ignition off. Remove following fuses from underhood fuse/relay block: PCM 1, ETC/ECM, INJ 1, INJ 2 and SBA fuse, if equipped. Probe fuse terminals in underhood fuse/relay block with a test light that is connected to a good ground. Does test light illuminate at any of fuse terminals? If yes, diagnose engine electrical system. If no, go to step 27.
7. Turn ignition off. Disconnect negative battery cable. Disconnect underhood fuse/relay block electrical connector that contains ignition 1 voltage circuit for ignition relay. Disconnect ignition switch electrical connector that contains ignition 1 voltage circuit for ignition relay. Reconnect negative battery cable. Test ignition 1 voltage circuit for a short to battery positive voltage. Did you find and correct condition? If yes, go to step 30. If no, go to next step.
8. Turn ignition off. Probe ignition 1 voltage terminal on ignition switch side of ignition switch electrical connector with a test light connected to a good ground. Does test light illuminate? If yes, go to step 28. If no, go to next step.
9. Test ignition 1 voltage bus bar circuit in underhood fuse/relay block for a short to battery positive voltage. Did you find a condition? If yes, go to step 29. If no, go to step 27.
10. Turn ignition off. Inspect 40-amp IGN "B" fuse in underhood fuse/relay block. Is fuse open? If yes, go to next step. If no, go to step 18.
11. Remove 40-amp IGN "B" fuse from underhood fuse/relay block. Probe both fuse terminals in underhood fuse/relay block with a test light that is connected to a good ground. Does test light illuminate on at least one fuse terminal? If yes, go to next step. If no, go to step 17.
12. Test ignition 1 voltage circuit between ignition switch and underhood fuse/relay block for a short to ground. Did you find and correct condition? If yes, go to step 30. If no, go to next step.
13. Test ignition switch assembly for a short to ground. Did you find a condition? If yes, go to step 28. If no, go to next step.
14. Test battery positive voltage circuit between underhood fuse/relay block and ignition switch for a short to ground. Did you find and correct condition? If yes, go to step 30. If no, go to next step.
15. Test battery positive voltage bus bar circuit of underhood fuse/relay block between 40-amp IGN "B" fuse and ignition switch for a short to ground. Did you find a condition? If yes, go to step 29. If no, go to next step.
16. Test ignition 1 voltage bus bar circuit of underhood fuse/relay block that contains ignition relay for a short to ground. Did you find a condition? If yes, go to step 29. If no, go to step 27.
17. Turn ignition off. Probe mounting stud for battery positive cable at underhood fuse/relay block with a test light connected to a good ground. Does test light illuminate? If yes, go to step 29. If no, diagnose engine electrical system.
18. Turn ignition off. Remove ignition relay from underhood fuse/relay block. Probe battery positive voltage circuit of ignition relay at underhood fuse/relay block with a test light connected to a good ground. Does test light illuminate? If yes, go to next step. If no, go to step 29.
19. Turn ignition on, with engine off. Probe ignition 1 voltage circuit of ignition relay at underhood fuse/relay block with a test light connected to a good ground. Does test light illuminate? If yes, go to step 23. If no, go to next step.
20. Turn ignition off. Test ignition 1 voltage circuit between ignition switch and underhood fuse/relay block for a high resistance or for an open. Did you find and correct condition? If yes, go to step 30. If no, go to next step.
21. Test ignition switch assembly for a high resistance or for an open. Did you find a condition? If yes, go to step 28. If no, go to next step.
22. Test battery positive voltage circuit between ignition switch and underhood fuse/relay block for a high resistance or for an open. Did you find and correct condition? If yes, go to step 30. If no, go to step 29.
23. Turn ignition on, with engine off. Probe coil ground circuit of ignition relay at underhood fuse/relay block with a test light connected to battery voltage. Does test light illuminate? If yes, go to step 25. If no, go to next step.
24. Turn ignition off. Disconnect negative battery cable at battery. Disconnect underhood fuse/relay block electrical connectors. Test coil ground circuit of ignition relay at underhood fuse/relay block electrical connector for a high resistance or for an open. Did you find and correct condition? If yes, go to step 30. If no, go to step 29.
25. Turn ignition off. Jumper ignition relay battery positive voltage circuit and ignition relay load circuit together at underhood fuse/relay block with a 20-amp fused jumper wire. Probe following fuses with a test light that is connected to a good ground: PCM 1, ETC/ECM, INJ 1, INJ 2 and SBA fuse, if equipped. Does test light illuminate on at least one test point of each fuse? If yes, go to next step. If no, go to step 29.
26. Test for an intermittent and for a poor connection at underhood fuse/relay block, ignition relay connector location. Did you find a condition? If yes, go to step 29. If no, go to next step.
27. Replace ignition relay. After replacing relay, go to step 30.
28. Replace ignition switch. After replacing ignition switch, go to step 30.
29. Replace underhood fuse/relay block. After replacing fuse/relay block, go to next step.
30. Replace any open fuses. Turn ignition off for 30 seconds. Attempt to start engine. Does engine start and run? If yes, go to next step. If no, go to «NO-START - ENGINE CRANKS OKAY»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-81l) under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
31. Clear DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Let engine reach operating temperature. Are re any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If no DTC(s) are set, system is okay.

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 - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

EXHAUST GAS RECIRCULATION

Note. For EGR system diagnosis, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 under DRIVE CYCLES in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL 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 appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

AVALANCHE

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SIERRA 2500HD

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SIERRA 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO 2500HD

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SUBURBAN

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

YUKON XL

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

See also:
• DIAGNOSTIC STARTING POINT - ENGINE CONTROLS
• NO-START DIAGNOSIS
• SYMPTOMS
• SENSOR OPERATING RANGE CHARTS - TRUCKS
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS
• FUEL SYSTEM PRESSURE TEST
• DRIVE CYCLES
• 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