Engine Controls - System & Component Testing: Other Chevrolet Tahoe II

TURBOCHARGER (6.5L & 6.6L DIESEL)

Note. 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 SELF-DIAGNOSTICS - 6.5L CAB & CHASSIS, CHEVY EXPRESS & SAVANA or SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article.

A malfunction in turbocharger boost system can set a related Diagnostic Trouble Code (DTC). For testing procedures, see SELF-DIAGNOSTICS - 6.5L CAB & CHASSIS, CHEVY EXPRESS & SAVANA or SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article.

PCM POWER & GROUND CHECK

Note. To identify circuits referenced in the following ground and power tests, see WIRING DIAGRAMS article.

Ground Circuits

PCM is located in right rear corner of engine compartment. Check PCM connectors for corroded or loose connections. Repair as necessary. Disconnect PCM connectors. Using DVOM, measure resistance between negative battery terminal and ground terminals at PCM harness connector. See WIRING DIAGRAMS article. 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 DVOM, check for battery voltage between chassis ground and continuous power terminal(s) at PCM harness connector(s). See «WIRING DIAGRAMS»(ref-142952) article. 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.

ENGINE SENSORS & SWITCHES

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 appropriate SELF-DIAGNOSTICS article.

BAROMETRIC PRESSURE SENSOR

A malfunction in Barometric Pressure (BARO) sensor can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

CAMSHAFT POSITION SENSOR

A malfunction in Camshaft Position (CMP) sensor can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

CRANKSHAFT POSITION SENSOR

A malfunction in Crankshaft Position (CKP) sensor can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

ENGINE COOLANT TEMPERATURE SENSOR

A malfunction in Engine Coolant Temperature (ECT) sensor circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS 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

ENGINE OIL LEVEL SWITCH

Note. Ensure oil level is okay before performing engine oil level switch diagnosis.

A malfunction in engine oil level switch circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

FUEL COMPOSITION SENSOR

Note. Fuel composition sensor is only used on models equipped with a flex-fuel 5.3L (RPO code L59).

Note. A malfunction in Fuel Composition (FC) sensor circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

1. Perform an accuracy test of Fuel Composition Tester (J 44175). Fill tester with acetone. Connect DMM to tester terminals. Set DMM to AC hertz scale and take a reading. Is reading 130-142 Hz? If yes, go to next step. If no, go to step 7 .
2. Perform a fuel test using fuel composition tester. Install a fuel pressure gauge into service port located on rear of injector rail. Start engine and open valve on pressure gauge. Allow enough fuel to pass through gauge to flush any previous fuel from inside hose. Draw fuel from fuel pressure gauge into beaker supplied with test kit. Transfer fuel from beaker into fuel tester. Turn ON fuel tester and note Red and Green LED. Is Green LED ON? If yes, go to step 4 . If no, go to next step.
3. Is Red LED ON? If yes, go to step 5 . If no, go to step 7 .
4. Connect DMM to fuel tester terminals. Set DMM to AC Hz scale and take a reading of fuel sample. Start engine and monitor fuel composition frequency on scan tool. Is reading from scan tool and DMM within 12 Hz? If yes, system is okay. If no, go to step 6 .
5. The fuel is contaminated. Drain fuel from tank. Replace fuel. Is action complete? If yes, system is okay.
6. Replace fuel composition sensor. Is action complete? If yes, system is okay.
7. Replace 9-volt battery and retest. If result is the same, tester will need to be sent out for repair.

FUEL TANK PRESSURE SENSOR

A Fuel Tank Pressure (FTP) sensor circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

HEATED OXYGEN SENSOR NO. 1

A malfunction in Heated Oxygen Sensor No. 1 (HO2S 1) circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

HEATED OXYGEN SENSOR NO. 2

A malfunction in Heated Oxygen Sensor No. 2 (HO2S 2) circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

INTAKE AIR TEMPERATURE SENSOR

Note. Intake Air Temperature (IAT) sensor may also be referred to as Manifold Air Temperature (MAT) sensor.

A malfunction in IAT sensor circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS 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 Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

MANIFOLD ABSOLUTE PRESSURE SENSOR (3.4L)

Note. For component locations, see COMPONENT LOCATIONS .

MANIFOLD ABSOLUTE PRESSURE SENSOR (EXCEPT 3.4L)

A malfunction in Manifold Absolute Pressure (MAP) sensor circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

MASS AIRFLOW SENSOR

A malfunction in Mass Airflow (MAF) sensor circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS 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 Diagnostic Trouble Code (DTC). For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

TRANSMISSION RANGE SWITCH

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

VEHICLE SPEED SENSOR

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

MOTORS, RELAYS & SOLENOIDS

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 appropriate SELF-DIAGNOSTICS 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 LOCK-OFF RELAY (BI-FUEL & CNG)

See FUEL LOCK-OFF RELAY testing procedure under FUEL SYSTEM (BI-FUEL & CNG).

FUEL PUMP RELAY (BI-FUEL & CNG)

See ALTERNATIVE FUEL PUMP RELAY testing procedure under FUEL SYSTEM (BI-FUEL & CNG).

FUEL PUMP RELAY (GASOLINE)

See appropriate FUEL PUMP RELAY testing procedure under FUEL SYSTEM (GASOLINE) .

GLOW PLUG RELAY

See GLOW PLUG SYSTEM DIAGNOSIS (6.5L) or GLOW PLUG SYSTEM DIAGNOSIS (6.6L) under FUEL SYSTEM (DIESEL).

IDLE AIR CONTROL VALVE

See IDLE AIR CONTROL SYSTEM DIAGNOSIS under IDLE CONTROL SYSTEM.

IGNITION RELAY

See appropriate IGNITION RELAY testing procedure under IGNITION SYSTEM .

FUEL SYSTEM (BI-FUEL & CNG)

Note. For component locations, see COMPONENT LOCATIONS .

FUEL SYSTEM UNWANTED SWITCH TO GASOLINE (BI-FUEL ONLY)

Note. For component locations, see COMPONENT LOCATIONS .

FUEL INDICATOR LIGHT ALWAYS ON - ALTERNATIVE FUELS

Note. For component locations, see COMPONENT LOCATIONS .

FUEL GAUGE INACCURATE OR INOPERATIVE - ALTERNATIVE FUELS

Note. For component locations, see COMPONENT LOCATIONS .

FUEL SYSTEM (DIESEL)

Note. Manufacturer does not provide testing procedures for many individual systems and component. For complete system testing and diagnosis, including fuel system testing not listed, see SELF-DIAGNOSTICS - DIESEL article.

FUEL LEAKS INSIDE OF ENGINE (6.6L)

Note. For component locations, see COMPONENT LOCATIONS .

Note. If directed here from FUEL RETURN SYSTEM DIAGNOSIS, go to step 15 . Step 15) will be performed with same components disconnected as stated in that test.

1. Disconnect fuel return line at engine. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
2. Remove air duct from air cleaner assembly to turbo inlet.
3. Remove air intake pipe.
4. Remove fuel return rubber hose of fuel injection pump from junction block. Cap fitting on block with a 3/8 inch rubber cap to prevent fuel leakage.
5. Install Vacuum Pump (J 23738-A) at fuel return pipe.
6. Apply 15 in. Hg of vacuum to pipe. If vacuum holds, reinstall disconnected components and go to step 22 . If vacuum does not hold, go to next step.
7. Remove generator. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
8. Disconnect fuel return line from right front cylinder head.
9. Install Black hose from (J 45873) onto each cylinder head return port.
10. Install (J 23738-A) onto each Black hose and apply 15 in. Hg of vacuum to each port and record if each side holds vacuum.
11. Perform lower valve cover removal procedure for bank(s) that did not hold vacuum. Then go to next step.
12. Connect fuel return lines on both cylinder heads. Tighten bolts to specification. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.
13. Install 3/8" Fuel Pipe Shutoff Valve (J 42964-1) to fuel return line.
14. Install Fuel Injector Cleaner (J 35800-A) on 3/8" Fuel Pipe Shutoff Valve (J 42964-1) port closest to fuel return line.
15. Ensure shutoff valve is closed.
16. Add 10 ounces of diesel fuel and 4 ounces of oil dye to (J 35800-A).
17. Connect shop air supply to (J 35800-A).
18. Adjust pressure regulator on (J 35800-A) to 15 psi.
19. Clean fuel injectors and fuel return lines with brake cleaning solvent and let dry.
20. Open valve on bottom of (J 35800-A) canister.
21. Inspect for leaks around fuel injectors and spill lines with High Intensity Black Light Kit (J 28428-E). Then go to step 29 .
22. Remove both upper valve covers. See «6.6L V8 DIESEL»(ref-136249) article in ENGINES.
23. Remove engine oil fill tube on front engine cover.
24. Install fuel injector feed pipes. Tighten fuel feed pipes to specification. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.
25. Add 8 ounces of oil dye to fuel tank. On dual tank systems add dye to front, or primary, tank.
26. Start engine.
27. Increase fuel pressure to 23,206 psi (160 MPa) with scan tool.
28. Inspect for leaks around fuel injectors and fuel injection pump drive gear with (J 28428-E). Then go to next step.
29. Tighten or replace any leaking components or gaskets.
30. Perform lower valve cover installation procedures as necessary. See «6.6L V8 DIESEL»(ref-136249) article in ENGINES.
31. Retest system for engine oil dilution by performing the following procedure: Drain engine oil from crankcase and refill. Run engine at idle for 10 minutes. Stop engine and wait 10 minutes, then check oil level on dipstick. This will be "Initial" oil level. Run engine at idle for 5 minutes while commanding fuel pressure to 23,206 psi (160 MPa) with scan tool. Stop engine and wait 10 minutes, then check oil level on dipstick. If engine oil level is not more than 3/16" above "Initial" oil level, system is okay. If engine oil level is more than 3/16" above "Initial" oil level, go to next step in this procedure. Run engine at idle again for 5 minutes while commanding fuel pressure to 23,206 psi (160 MPa) with scan tool. Stop engine and wait 10 minutes, then check oil level on dipstick. If engine oil level is not more than 3/16" above last oil level checked, system is okay. If engine oil level is more than 3/16" above last oil level checked, condition still exists. Go back to step 1 .

FUEL LEAKS OUTSIDE OF ENGINE (6.6L)

Note. For component locations, see COMPONENT LOCATIONS .

1. Remove upper intake manifold sight shield using following procedure: Remove retaining bolt in front of shield. Lift up on front of shield. Lift shield off rear bracket.
2. Clean all fuel lines between fuel injection pump and fuel injectors using brake cleaning solvent, and let dry.
3. Add 8 ounces of oil dye to fuel tank. On dual tanks, add dye to front, or primary tank.
4. Connect scan tool to Data Link Connector (DLC).
5. Start and idle engine for 3-5 minutes.
6. Command fuel pressure control to 23,206 psi (160 MPa) with scan tool.
7. Inspect for fuel leaks around fuel injection pump, junction block, fuel rails, and fuel injector supply lines with High Intensity Black Light Kit (J 28428-E). Tighten or replace any leaking lines or components. See «6.6L V8 DIESEL»(ref-136249) article in ENGINES, or appropriate REMOVAL, OVERHAUL & INSTALLATION article.

From Engine To Tank

1. Disconnect return line at engine, metal collar. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
2. Remove fuel filler cap.
3. Apply 1 psi air at fuel return line that leads back to tank.
4. Listen at filler tube for air.
5. If air is present, return line is okay. If air is not present, disconnect return line at sender assembly.
6. Retest using 1 psi at fuel return line back to tank. If air is present, return line is okay. Check and replace sender assembly. If air is not present, repair restriction in return line.

From Engine To Injector Spill Lines

1. Disconnect fuel return line at engine. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
2. Remove air duct from air cleaner assembly to turbo inlet.
3. Remove air intake pipe.
4. Remove fuel return rubber hose of fuel injection pump from junction block. Cap fitting on block with a 3/8" rubber cap to prevent fuel leakage.
5. Install Vacuum Pump (J 23738-A) at fuel return pipe.
6. Apply 15 in. Hg of vacuum to pipe. If vacuum holds, go to step 13 . If vacuum does not hold, go to next step.
7. Remove generator. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
8. Remove fuel return line connecting right front and left rear cylinder heads.
9. Install (J 23738-A) onto right front cylinder head return port.
10. Apply 15 in. Hg of vacuum to port. If vacuum holds, go to next step. If vacuum does not hold, leak is in spill lines under valve cover. Install fuel return line between cylinder heads, remove lower right valve cover, and go to step 15 of FUEL LEAKS INSIDE OF ENGINE. For lower right side valve cover removal and installation, see «6.6L V8 DIESEL»(ref-136249) article in ENGINES.
11. Install (J 23738-A) onto left rear cylinder head return port.
12. Apply 15 in. Hg of vacuum to port. If vacuum holds, replace leaking fuel return line between cylinder heads. If vacuum does not hold, leak is in spill lines under valve cover. Install fuel return line between cylinder heads, remove lower left valve cover, and go to step 15 of FUEL LEAKS INSIDE OF ENGINE. For lower left side valve cover removal and installation, see «6.6L V8 DIESEL»(ref-136249) article in ENGINES.
13. Remove cap from junction block.
14. Reinstall fuel injection pump fuel return hose on junction block and clamp hose.
15. Install air duct on air cleaner assembly to turbo inlet.
16. Install air intake pipe.
17. Reinstall fuel return line to engine.
18. Install generator.
19. Start and idle engine and check for leaks.

Preliminary Checks

If fuel supply system is not delivering enough fuel driveability could be greatly affected. If air is being drawn into fuel injection system a NO-START - ENGINE CRANKS OKAY or a HARD START symptom could exist. If another diagnosis indicates, or if fuel supply system is suspected of not delivering enough fuel or drawing air, the following systems should be checked

1. Any air leaks or restrictions between fuel injection pump and fuel tank will seriously affect pump output.
2. Insufficient fuel in fuel tank.
3. Any loose fuel component connections.
4. Any hoses and lines that are flattening when engine is running, or have kinks that would restrict flow of fuel.

Fuel System Air Leak Check

1. Install Vacuum Gauge (J 44638) to fuel system service port on right front side of engine.
2. Remove air duct from air cleaner assembly to turbo inlet.
3. Remove generator for visibility of fuel supply lines. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
4. Prime fuel manager until 10 psi is indicated on (J 44638).
5. Check for external fuel leaks between fuel filter/heater assembly and fuel injection pump. If fuel is leaking externally, replace or repair leaking component. If no external fuel leaks are found, go to next step.
6. Reprime fuel system until 10 psi is indicated on (J 44638). If fuel pressure drops from 10 psi to 2 psi in less than one minute, go to step 23 . If fuel pressure drops from 10 psi to 2 psi in more than one minute, go to next step.
7. Disconnect fuel supply line at engine. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
8. Cap off fuel supply pipe on engine with a 1/2" rubber plug and clamp.
9. Disconnect fuel return line at engine. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
10. Install Mityvac (J 23738-A) on fuel return pipe on engine.
11. Check fuel system components on top of engine for vacuum leaks. NOTE: There is an orifice in fuel injection pump between fuel supply and fuel return systems. This will delay vacuum being pulled from fuel supply lines. Apply at least 25 inches of Hg of vacuum to fuel return pipe with (J 23738-A) and wait more than one minute for system to stabilize. Repeat this step 6 times. Observe (J 23738-A). If vacuum does not drop to less than 8 in. Hg within 10 minutes, go to next step. If vacuum drops to less than 8 in. Hg within 10 minutes, go to step 18 .
12. Reconnect fuel supply line and return line at engine.
13. Install a transparent hose between Fuel Injection Control Module (FICM) outlet and fuel filter inlet, with a vertical loop to observe incoming fuel for air bubbles.
14. Install generator.
15. Prime fuel system 30 times to remove air from fuel hoses.
16. Start and run engine.
17. Observe fuel in transparent hose for air bubbles. If there are no air bubbles of any kind entering transparent hose with incoming fuel, fuel suction system is okay. Go to step 28 . If any air bubbles are entering transparent hose with incoming fuel, stop engine and go to step 19 .
18. Check fuel injection pump and on-engine fuel suction system for air leakage. Disconnect fuel outlet hose from outlet pipe of fuel filter assembly. Open drain on fuel filter assembly and drain fuel into a suitable container. Close drain. Install (J 23738-A) on outlet port of fuel filter assembly. Apply 15 in. Hg of vacuum to fuel pipe and observe (J 23738-A). If vacuum does not drop, connect fuel supply line at engine and go to step F . If vacuum drops, repair air leak between fuel supply line fitting and fuel filter assembly. Remove (J 23738-A) from outlet port of fuel filter assembly and install (J 23738-A) to fuel outlet hose. Remove air intake pipe. Remove supply hose from fuel injection pump and plug hose. Apply 15 in. Hg of vacuum and observe reading. If vacuum drops, repair leak between fuel filter assembly outlet and fuel injection pump inlet. If vacuum does not drop, go to step J . Disconnect fuel injection pump return hose. Cap off fuel return pipe on fuel injection pump with a 5/16" rubber plug, and clamp plug. Install (J 23738-A) to fuel inlet pipe of fuel injection pump. Apply 20 in. Hg of vacuum and observe (J 23738-A). If vacuum drops, replace fuel injection pump, then go to step 28 . If vacuum does not drop, replace fuel injection pump inlet supply hose, then go to step 28 .
19. Check fuel sender for air leakage. Remove front fuel tank. Remove fuel sender from fuel tank. Remove strainer from fuel sender and plug bottom end of pickup tube. Apply 15 in. Hg of vacuum to upper end of pickup tube and observe (J 23738-A). If vacuum holds, inspect "O" ring sealing surfaces of fuel sending unit and chassis fuel line for damage and correct as necessary. If sealing surfaces are not damaged, replace fuel line between chassis line and fuel sending unit, then go to next step. If vacuum does not hold, replace fuel sender. Reinstall fuel tank and go to next step.
20. Prime fuel system 30 times or until fuel pressure is 10 psi to remove air from fuel system. Air will be forced out of system within 2 minutes.
21. Start and run engine.
22. Observe fuel for air bubbles. If there are no air bubbles of any kind entering transparent hose with incoming fuel, fuel suction system is okay. Go to step 28 . If any air bubbles are entering transparent hose with incoming fuel, stop engine and go to step 8 .
23. Prime fuel system 30 times or until fuel pressure is 10 psi to remove air from fuel system. Air will be forced out of system within 2 minutes.
24. Remove hose from fuel filter assembly outlet fitting and plug hose.
25. Verify (J 44638) is installed.
26. Remove Ignition 1 relay.
27. Crank engine 2-3 times in 15 second intervals and observe (J 44638). If (J 44638) indicates 5 in. Hg of vacuum or more, go to next step. If (J 44638) indicates less than 5 in. Hg of vacuum, replace fuel injection pump, then go to next step.
28. Remove transparent hose if necessary and attach any disconnected components or fuel lines.
29. Prime fuel system 30 times to remove air in fuel hoses.
30. Clean any fuel spillage.
31. Start engine. If engine starts and stalls, repeat step 29 .
32. Run engine to check for fuel leakage.
33. Verify customer concern is corrected. If customer concern is not corrected, go to «SYMPTOM DIAGNOSIS»(ref-149956-S01569150402002110400000) under SYMPTOMS (DIESEL) in TROUBLE SHOOTING - NO CODES - TRUCKS article.

If fuel supply system is not delivering enough fuel driveability could be greatly affected. If air is being drawn into fuel injection system a NO-START - ENGINE CRANKS OKAY or a HARD START symptom could exist. If another diagnosis indicates, or if fuel supply system is suspected of not delivering enough fuel or drawing air, THE following systems should be checked

1. Any air leaks or restrictions between fuel injection pump and fuel tank will seriously affect pump output.
2. Insufficient fuel in fuel tank.
3. Any loose fuel component connections.
4. Any hoses and lines that are flattening when engine is running, or have kinks that would restrict flow of fuel.

1. Install Vacuum Gauge (J 44638) to fuel system service port on right front side of engine.
2. Remove air duct from air cleaner assembly to turbo inlet.
3. Remove generator for visibility of fuel supply lines. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
4. Prime fuel manager until 10 psi is indicated on (J 44638).
5. Check for external fuel leaks between fuel filter/heater assembly and fuel injection pump. If fuel is leaking externally, replace or repair leaking component. If no external fuel leaks are found, go to next step.
6. Reprime fuel system until 10 psi is indicated on (J 44638). If fuel pressure drops from 10 psi to 2 psi in less than one minute, go to step 24 . If fuel pressure drops from 10 psi to 2 psi in more than one minute, go to next step.
7. Disconnect fuel supply line at engine. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
8. Cap off fuel supply pipe on engine with a 1/2" rubber plug and clamp.
9. Disconnect fuel return line at engine. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
10. Install Mityvac (J 23738-A) on fuel return pipe on engine.
11. Check fuel system components on top of engine for vacuum leaks. NOTE: There is an orifice in fuel injection pump between fuel supply and fuel return systems. This will delay vacuum being pulled from fuel supply lines. Apply at least 25 inches of Hg of vacuum to fuel return pipe with (J 23738-A) and wait more than one minute for system to stabilize. Repeat this step 6 times. Observe (J 23738-A). If vacuum does not drop to less than 8 in. Hg within 10 minutes, go to next step. If vacuum drops to less than 8 in. Hg within 10 minutes, go to step 22 .
12. Reconnect fuel supply line and return line at engine.
13. Disconnect chassis fuel line from short fuel line between fuel sender and chassis fuel line in front of fuel tank. See QUICK CONNECT FITTINGS (METAL COLLAR) under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article.
14. Plug chassis fuel line using a 1/2" rubber plug and clamp plug.
15. Check fuel system components on top of engine for vacuum leaks. Apply at least 25 in. Hg of vacuum to fuel return pipe with (J 23738-A) and wait more than one minute for system to stabilize. Repeat this step 10 times. Observe (J 23738-A). If vacuum does not drop below 8 in. Hg within 10 minutes, go to next step. If vacuum does drop below 8 in. Hg within 10 minutes, inspect "O" ring sealing surfaces of engine fuel supply line for damage and correct as necessary. If sealing surfaces are not damaged, replace chassis fuel lines and go to step 29 .
16. Reconnect fuel line at fuel tank and fuel return line at engine.
17. Install a transparent hose between Fuel Injection Control Module (FICM) outlet and fuel filter inlet, with a vertical loop to observe incoming fuel for air bubbles.
18. Install generator.
19. Prime fuel system 30 times to remove air from fuel hoses.
20. Start and idle engine.
21. Observe fuel in transparent hose for air bubbles. If there are no air bubbles of any kind entering transparent hose with incoming fuel, fuel suction system is okay. Go to step 29 . If any air bubbles are entering transparent hose with incoming fuel, stop engine and go to step 23 .
22. Check fuel injection pump and on-engine fuel suction system for air leakage. Disconnect fuel outlet hose from outlet pipe of fuel filter assembly. Open drain on fuel filter assembly and drain fuel into a suitable container. Close drain. Install (J 23738-A) on outlet port of fuel filter assembly. Apply 15 in. Hg of vacuum to fuel pipe and observe (J 23738-A). If vacuum does not drop, connect fuel supply line at engine and go to step F . If vacuum drops, repair air leak between fuel supply line fitting and fuel filter assembly. Remove (J 23738-A) from outlet port of fuel filter assembly and install (J 23738-A) to fuel outlet hose. Remove air intake pipe. Remove supply hose from fuel injection pump and plug hose. Apply 15 in. Hg of vacuum and observe reading. If vacuum drops, repair leak between fuel filter assembly outlet and fuel injection pump inlet. If vacuum does not drop, go to step J . Disconnect fuel injection pump return hose. Cap off fuel return pipe on fuel injection pump with a 1/2" rubber plug, and clamp plug. Install (J 23738-A) to fuel inlet pipe of fuel injection pump. Apply 20 in. Hg of vacuum and observe (J 23738-A). If vacuum drops, replace fuel injection pump, then go to step 29 . If vacuum does not drop, replace fuel injection pump inlet supply hose, then go to step 29 .
23. Check fuel sender for air leakage. Remove front fuel tank. Remove fuel sender from fuel tank. Remove strainer from fuel sender and plug bottom end of pickup tube. Apply 15 in. Hg of vacuum to upper end of pickup tube and observe (J 23738-A). If vacuum holds, inspect "O" ring sealing surfaces of fuel sending unit and chassis fuel line for damage and correct as necessary. If sealing surfaces are not damaged, replace fuel line between chassis line and fuel sending unit, then go to step 29 . If vacuum does not hold, replace fuel sender. Reinstall fuel tank and go to step 29 .
24. Prime fuel system 30 times or until fuel pressure is 10 psi to remove air from fuel system. Air will be forced out of system within 2 minutes.
25. Remove hose from fuel filter assembly outlet fitting and plug hose.
26. Verify (J 44638) is installed.
27. Remove Ignition 1 relay.
28. Crank engine 2-3 times in 15 second intervals and observe (J 44638). If (J 44638) indicates 5 in. Hg of vacuum or more, go to step 6 . If (J 44638) indicates less than 5 in. Hg of vacuum, replace fuel injection pump, then go to next step.
29. Remove transparent hose if necessary and attach any disconnected components or fuel lines.
30. Prime fuel system 30 times to remove air in fuel hoses.
31. Clean any fuel spillage.
32. Start engine. If engine starts and stalls, repeat step 30 .
33. Run engine to check for fuel leakage.
34. Verify customer concern is corrected. If customer concern is not corrected, go to «SYMPTOM DIAGNOSIS»(ref-149956-S01569150402002110400000) under SYMPTOMS (DIESEL) in TROUBLE SHOOTING - NO CODES - TRUCKS article.

Fuel Pressure Regulator Graphing

Note. For fuel pressure regulator graphing examples using scan tool (Scheme 6)- (Scheme 8).

1. Set up scan tool in the following format: Select Data Display on scan tool. Select Engine Data 1. Select More softkey 2 times. Select Live Plot softkey. Select Engine Speed, Actual Fuel Rail Pressure, and Desired Fuel Rail Pressure parameters by highlighting each parameter and depressing ENTER softkey. Select Accept softkey. Select More softkey, then select Change Min/Max softkey. Select More softkey, and adjust parameters to the following Min/Max ranges: Engine Speed Min/Max range is 0-1000 RPM. Actual Fuel Rail Pressure Min/Max range is 1-160 MPa. Desired Fuel Rail Pressure Min/Max range is 1-160 MPa.
2. Start and idle engine.
3. Observe live plot for sharp changes in Actual Fuel Rail Pressure above and below Desired Fuel Rail Pressure while performing one of the following actions: Idling engine. Shifting transmission from Park to Drive, and back to Park. Turning steering wheel from lock to lock. Turning air conditioning ON and OFF.
4. If there is a violent fluctuation in Actual Fuel Rail pressure, as seen in (Scheme 8), replace fuel pressure regulator.

Scheme 6

Scheme 7

Scheme 8

Diagnosis of fuel odor may be a condition of a leaking fuel tank, filler neck or filler cap. A defective filler cap, a plugged or pinched vent pipe can cause a collapsed fuel tank. Loose mounting straps or foreign material in tank may be cause of a rattle at fuel tank.

IGNITION (GLOW PLUG) RELAY (6.6L)

Note. For component locations, see COMPONENT LOCATIONS .

WATER-IN-FUEL LIGHT ALWAYS ON (6.5L)

Note. For component locations, see COMPONENT LOCATIONS .

WATER-IN-FUEL LIGHT INOPERATIVE (6.5L)

Note. For component locations, see COMPONENT LOCATIONS .

WATER-IN-FUEL LIGHT ALWAYS ON (6.6L)

Note. For component locations, see COMPONENT LOCATIONS .

WATER-IN-FUEL LIGHT INOPERATIVE (6.6L)

Note. For component locations, see COMPONENT LOCATIONS .

FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L)

Note. For component locations, see COMPONENT LOCATIONS .

FUEL PUMP RELAY (2.2L & 3.0L VUE)

A malfunction in fuel pump relay or circuit can set a Diagnostic Trouble Code (DTC). For testing procedures and specifications, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SATURN VUE or SELF-DIAGNOSTICS - 3.0L SATURN VUE article.

FUEL PUMP RELAY (3.4L)

Note. For component locations, see COMPONENT LOCATIONS .

FUEL PUMP RELAY (5.0L & 5.7L)

Note. For component locations, see COMPONENT LOCATIONS .

IDLE CONTROL SYSTEM

Note. For idle control system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

IGNITION SYSTEM

Note. For ignition system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

EMISSION SYSTEMS & SUB-SYSTEMS (GASOLINE)

Note. For emission and subsystem testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Electric AIR Pump

Note. For electric AIR pump testing, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

EXHAUST GAS RECIRCULATION

Note. Manufacturer does not provide testing procedures for many individual systems and components. For EGR system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Note. For EGR system diagnosis, see appropriate INSPECTION/MAINTENANCE PROCEDURES in appropriate SELF-DIAGNOSTICS article.

FUEL EVAPORATION

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

EVAPORATIVE EMISSION SYSTEM CLEANING

Note. For component locations, see COMPONENT LOCATIONS .

Cleaning Procedure

1. Remove EVAP canister.
2. Turn OFF main valve on EVAP Pressure/Purge Diagnostic Station (J 41413).
3. Disconnect hose from diagnostic station pressure regulator.
4. Using a section of vacuum hose, connect one end onto diagnostic station pressure regulator.
5. Connect other end of vacuum hose to canister side of purge pipe.
6. Turn ON main nitrogen cylinder valve and continue to discharge nitrogen for 15 seconds.
7. If nitrogen does not dislodge carbon particles, replace purge pipe.
8. Return EVAP pressure/purge diagnostic station to original condition of station.
9. Install a new EVAP canister.
10. Connect all previously disconnected EVAP pipe connectors.
11. Lower vehicle.
12. Return to appropriate DTC service procedure.

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.

EMISSION SYSTEMS & SUB-SYSTEMS (DIESEL)

Note. For emission and subsystem testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

CRANKCASE DEPRESSION REGULATOR VALVE (6.5L)

The purpose of Crankcase Depression Regulator (CDR) valve is to maintain 0-4 in. H 2 O (0-0.996 kPa) vacuum in crankcase at all engine speeds, assuming that piston/ring combustion blow-by is not excessive (less than 4 cm). Too little vacuum will tend to force oil leaks. CDR valve is checked with a water manometer. A "U" tube manometer indicates pressure or vacuum by difference in height of 2 columns of fluid. If crankcase vacuum is more than 4 in. H 2 O (0.996 kPa), dirt or dust can be pulled into crankcase cavity through front/rear crankcase seal, etc. and contaminate oil. If crankcase pressure is positive, engine oil leaks are likely to occur around engine seals and gaskets.

1. Connect one end of manometer to engine oil dipstick hole. The other end of manometer is vented to atmosphere.
2. Unplug rubber vent tube from turbo inlet elbow.
3. Run engine through a no-load speed range (gear selector in PARK) and observe manometer readings. If manometer reading is 4 in. H 2 O (0.996 kPa) or less positive pressure, reconnect CDR system and proceed to next step. If manometer reading is higher than 4 in. H 2 O (0.996 kPa) positive pressure, this indicates that there is an internal engine problem.
4. Install air cleaner.
5. Start engine and observe manometer (vacuum) reading. Manometer reading should be approximately 0-1 in. H 2 O (0.249 kPa) at idle to approximately 3-5 in. H 2 O (0.747-1.245 kPa) at 2000 RPM. Add amount that manometer column travels up, to amount that column travels down, in order to obtain total water pressure (vacuum).

POSITIVE CRANKCASE VENTILATION (6.6L)

During normal operation, crankcase gases can be seen exiting from hose at oil separator. Maximum crankcase pressure is 16 in. H 2 O (4 kPa) at 3100 RPM measured at oil level indicator tube.

1. Oil Leak (External) Check the following: Plugged or kinked crankcase ventilation system hoses. Damaged or loose crankcase ventilation system hoses. Valve rocker arm diaphragm covers loose. Oil separator oil drain hose damaged or loose. Too much crankcase pressure.
2. PVC Check Valve Stuck Closed Check The following: Valve closes when 0.213 psi (1.47 kPa) of crankcase pressure is applied from crankcase side (bottom) of valve. Valve should allow oil to drain from separator during idle and engine off conditions. Inspect for proper operation by stopping engine and waiting 5 minutes to allow oil to drain back into crankcase. Remove drain hose from check valve. If more than residual oil (several drops) drains from separator, replace valve.
3. Odors Normal situation.
4. Noise Cracked hoses.
5. Smoke Internal engine failure.

EGR Valve Check

With engine off, disconnect vacuum hose to EGR valve. Connect vacuum pump to EGR and apply 10 in. Hg. vacuum. EGR diaphragm should move up and stay up for at least 20 seconds. If EGR does not operate as specified, replace EGR valve.

Exhaust Gas Recirculation System Cleaning

1. Remove Exhaust Gas Recirculation (EGR) valve.
2. Depress pintle several times using a pencil eraser or other suitable soft instrument. Pintle should move in and out smoothly. Replace valve if valve exhibits tendencies to stick.
3. Try to rotate EGR valve electrical connector housing. Repeat for coil housing. Replace valve if valve exhibits any looseness. Inspect EGR valve pintle and seat for deposits. Use a cloth or other suitable soft device to remove deposits. Remove all loose particles. Replace valve if deposits are such that pintle-to-base interface cannot be cleaned adequately to allow pintle to seal against seat. Damage to powdered metal EGR valve base occurs if cleaned with solvents, sharp tools, wire brush or wheel, or sand blasting. Cleaning by these methods is not recommended.
4. Clean passages with a wire brush. Remove all loose particles.
5. Install EGR valve.

MISCELLANEOUS CONTROLS

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 appropriate SELF-DIAGNOSTICS 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 WIRING DIAGRAMS article for terminal and wire color identification.

ELECTRIC COOLING FAN CONTROL

Note. For electric cooling fan circuit testing, see ELECTRIC COOLING FANS article in AIR CONDITIONING & HEATING. See WIRING DIAGRAMS article 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 WIRING DIAGRAMS article.

2.2L (VIN 4) "S" SERIES

COMPONENT LOCATIONS 2.2L (VIN 4) SONOMA & S10 PICKUP

3.4L (VIN E) "A" & "B" SERIES

COMPONENT LOCATIONS 3.4L (VIN E) "A" & "B" SERIES

3.4L (VIN E) "U" SERIES

COMPONENT LOCATIONS 3.4L (VIN E) "U" SERIES

4.2L (VIN S) "S" & "T" SERIES

COMPONENT LOCATIONS 4.2L (VIN S) "S" & "T" SERIES

4.3L (VIN W) "C" & "K" SERIES

COMPONENT LOCATIONS 4.3L (VIN W) "C" & "K" SERIES

4.3L (VIN W) "G" SERIES

COMPONENT LOCATIONS 4.3L (VIN W) "G" SERIES

4.3L (VIN W) "L" & "M" SERIES

COMPONENT LOCATIONS 4.3L (VIN W) "L" & "M" SERIES

4.3L (VIN W) "S" & "T" SERIES

COMPONENT LOCATIONS 4.3L (VIN W) "S" & "T" SERIES

4.8L (VIN V), 5.3L (VIN T & Z), & 6.0L (VIN U) "C" & "K" SERIES

COMPONENT LOCATIONS 4.8L (VIN V), 5.3L (VIN T & Z), & 6.0L (VIN U) "C" & "K" SERIES

5.0L (VIN M) & 5.7L (VIN R) "G" SERIES

COMPONENT LOCATIONS 5.0L (VIN M) & 5.7L (VIN R) "G" SERIES

6.5L (VIN F) "C" SERIES

COMPONENT LOCATIONS 6.5L (VIN F) "C" SERIES

6.5L (VIN F) "G" SERIES

COMPONENT LOCATIONS 6.5L (VIN F) "G" SERIES

6.6L (VIN 1) "C" & "K" SERIES

COMPONENT LOCATIONS 6.6L (VIN 1) "C" & "K" SERIES

8.1L (VIN G) "C" & "K" SERIES

COMPONENT LOCATIONS 8.1L (VIN G) "C" & "K" SERIES

8.1L (VIN G) "G" SERIES

COMPONENT LOCATIONS 8.1L (VIN G) "G" SERIES