Engine Controls - System & Component Testing - 6.6L: Diagnosis Chevrolet Silverado 1500 HD

Diagnostic Procedures

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROL»(ref-158516-S41425574832003100300000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Turn ignition on, with engine off. Remove underhood fuse/relay block cover. Using a test light connected to ground, probe the following fuses: INJ "B" fuse, FUEL HT fuse and SBA fuse (if equipped). Does the test light illuminate on at least one test point of each fuse? If yes, go to next step. If no, go to step 9 .
3. Turn ignition off. Using test light connected to ground, probe both test points of the 25-amp INJ "B" fuse. Does the test light illuminate on either test point of the fuse? If yes, go to next step. If no, go to step 24 .
4. Turn ignition off. Remove the ignition relay from the underhood fuse/relay. Using test light connected to battery voltage, probe the coil ground circuit of the ignition relay. Does the test light illuminate? If yes, go to next step. If no, go to step 7 .
5. Turn ignition off. Disconnect negative battery cable at the battery. Disconnect the underhood fuse/relay block electrical connector that contains the ground wire for the ignition relay. Disconnect ECM electrical connector that contains the ground wire for the ignition relay. Test the coil ground wire of the ignition relay for a short to ground. Did you find and correct the condition? If yes, go to step 24 . If no, go to next step.
6. Test the ignition relay coil ground bus bar circuit of the underhood fuse/relay block for a short to ground. Did you find a condition? If yes, go to step 23 . If no, go to next step.
7. Test the relay load bus bar circuit of the underhood fuse/relay block between the ignition relay and fuses to the circuit components for a short to battery positive voltage. Did you find a condition? If yes, go to step 23 . If no, go to next step.
8. Turn ignition off. Remove INJ "B" fuse, FUEL HT fuse and SBA fuse (if equipped) from the underhood fuse/relay block. Using test light connected to ground, probe all these fuse terminals. Does the test light illuminate at any of the fuse terminals? If yes, diagnose electrical system. If no, go to step 21 .
9. Turn ignition on, with engine off. Probe both test points of the 20-amp ECM "B" fuse in the underhood fuse/relay block with test light connected to a good ground. Does the test light illuminate on both test points of the fuse? If yes, go to step 13 . If no, go to next step.
10. Does test light illuminate on one test point of the 20-amp ECM "B" fuse? If yes, go to next step. If no, go to step 12 .
11. Test the battery positive voltage bus bar circuit of the underhood fuse/relay block between the 20-amp ECM "B" fuse and the 15-amp INJ "B" fuse for a short to ground. Did you find a condition? If yes, go to step 23 . If no, go to step 21 .
12. Turn ignition off. Probe the mounting stud for the battery positive cable at the underhood fuse/relay block with a test light connected to a good ground. Does the test light illuminate? If yes, go to step 23 . If no, diagnose electrical system.
13. Turn ignition off. Remove ignition relay from the 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 23 .
14. Turn ignition on. 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 next step. If no, go to step 23 .
15. Turn ignition on, with engine off. Probe coil ground circuit of ignition relay at underhood fuse/relay block with a test light connected to a battery positive voltage. Does test light illuminate? If yes, go to step 18 . If no, go to next step.
16. Turn ignition off. Disconnect negative battery cable at the battery. Disconnect the underhood fuse/relay block electrical connector that contains the ground wire for the ignition relay. Disconnect ECM electrical connector that contains the ground wire for the ignition relay. Test coil ground wire of ignition relay for a high resistance or an open. Did you find and correct the condition? If yes, go to step 24 . If no, go to next step.
17. Test ignition relay coil ground bus bar circuit of the underhood fuse/relay block for a high resistance or an open. Did you find a condition? If yes, go to step 23 . If no, go to step 20 .
18. Turn ignition off. Jumper the ignition relay battery positive voltage circuit and ignition relay load circuit together at the underhood fuse/relay block with a 20-amp fused jumper wire. Using a test light connected to ground, probe INJ "B" fuse, HT FUEL fuse and SBA fuse (if equipped). Does the test light illuminate on at least one test point of each fuse? If yes, go to next step. If no, go to step 23 .
19. Test for an intermittent and for a poor connection at the underhood fuse/relay block ignition relay connector location. Did you find a condition? If yes, go to step 23 . If no, go to step 21 .
20. Test for an intermittent and for a poor connection at the ECM connectors. Did you find a condition? If yes, go to step 24 . If no, go to step 22 .
21. Replace ignition relay. After replacing relay, go to step 24 .
22. Replace ECM. See «ENGINE CONTROL MODULE»(ref-158072-S21888722262003090900000) under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - SIERRA & SILVERADO - DIESEL article. Reprogram ECM. After repairs, go to step 24 .
23. Replace the underhood fuse/relay block assembly. After repairs, go to next step.
24. 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, refer to «NO-START - ENGINE CRANKS OKAY»(ref-152810-S12734170322003022600000) under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article.
25. Clear DTCs with scan tool. Operate vehicle for 5 minutes. Does a DTC set during this ignition cycle? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158516-S25875883752003100300000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If no, system is okay.

1. Is the WATER IN FUEL light operating properly? If yes, go to next step. If no, diagnose warning light.
2. Turn ignition off. Disconnect the fuel heater harness connector from the top of the fuel filter/heater element housing. Turn ignition on, with engine off. Using a test light connected to ground, probe the fuel heater ignition 1 voltage circuit. Does the test light illuminate? If yes, go to next step. If no, go to step 5 .
3. Using test light connected to battery voltage, probe the fuel heater ground circuit at the fuel filter/heater element housing. Does the test light illuminate? If yes, go to next step. If no, go to step 10 .
4. Remove fuel filter from the fuel filter/heater element housing, mounted on valve cover. Test the ignition 1 voltage circuit and ground circuit for an open in the fuel filter/heater element housing. Did either circuit test open? If yes, go to step 11 . If no, go to step 7 .
5. Is the fuel HT fuse open? If yes, go to next step. If no, go to step 8 .
6. Disconnect the intake air heater harness connector. Probe the ignition 1 voltage circuit with a test light connected to battery voltage. Does the test light illuminate? If yes, go to step 9 . If no, go to next step.
7. Remove the fuel filter/heater element housing from vehicle. On a bench, cool the sensor part of the fuel heater with ice. With the fuel heater below 46°F (8°C), wet the heating element with fuel. Connect ignition 1 voltage circuit of the fuel heater to battery voltage and connect ground circuit of the fuel heater to ground on the top of the housing. Observe the heating element. Does heat occur? If yes, go to step 13 . If no, go to step 12 .
8. Repair open in the ignition 1 voltage circuit between the fuel filter/heater element housing and fuse. Did you complete the repair? If yes, go to step 14 .
9. Repair short to ground on the ignition 1 voltage circuit. After repairs, go to step 14 .
10. Repair open in the ground circuit between the fuel filter/heater element housing and chassis ground. After repairs, go to step 14 .
11. Replace fuel filter/heater element housing. After replacing fuel filter/heater element housing, go to step 14 .
12. Replace fuel heater. Fuel heater is located on fuel filter/heater element housing and is mounted on valve cover. After replacing fuel heater, go to step 14 .
13. Replace intake air heater relay. Relay is located in glow plug controller housing, on upper intake manifold. After replacing relay, go to next step.
14. Operate vehicle under which the problem was noted. Does the system operate properly? If yes, system is okay. If no, go to step 1 .

1. Is the WATER IN FUEL light operating properly? If yes, go to next step. If no, diagnose warning light.
2. Disconnect the fuel heater connector and remove fuel heater from filter housing. Filter housing is mounted on valve cover. With fuel heater at room temperature, connect the ignition 1 voltage circuit of the fuel heater to battery voltage and connect ground circuit of the fuel heater to ground. Observe heater element. Does heat occur? If yes, go to step 4 . If no, go to next step.
3. Cool the sensor part of the fuel heater with ice. With the fuel heater below 46°F (8°C), wet the heating element with fuel. Connect ignition 1 voltage circuit of the fuel heater to battery voltage and connect ground circuit of the fuel heater to ground. Observe the heating element. Does heat occur? If yes, go to step 5 . If no, go to next step.
4. Replace fuel heater. Fuel heater is located on fuel filter/heater element housing and is mounted on valve cover. After replacing fuel heater, go to next step.
5. Operate vehicle under which the problem was noted. Does the system operate properly? If yes, system is okay. If no, go to step 1 .

FUEL INJECTOR BALANCE TEST WITH TECH 2

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

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROL»(ref-158516-S41425574832003100300000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Are any DTCs set other than P0300, P0301-P0308? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158516-S25875883752003100300000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If no, go to next step.
3. Start and operate engine at idle. Using scan tool, observe the Balancing Rate Cyl.1-8 parameters. Are all of the Balancing Rate parameters within -4 mm 3 and +4 mm 3 ? If yes, go to step 5 . If no, go to next step.
4. Graph the Fuel Pressure Regulator. Refer to «FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE»(ref-152810-S21775685432003022800000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article. Is fuel pressure regulator graph normal? If yes, go to step 6 . If no, go to step 8 .
5. Observe engine speed or other customer concern. Using scan tool, perform Cylinder Power Balance Test in Special Functions. Do any of the cylinders indicate a different engine speed change than the others, or lessen the customer's concern? If yes, go to next step. If no, system is okay.
6. Perform engine compression test. Do any of the cylinders have low compression? If yes, diagnose engine mechanical problem. If no, go to next step.
7. Replace faulty fuel injectors on cylinders that had poor RPM drop, high balance rates, or a noise/smoke change. See «FUEL INJECTOR»(ref-158072-S30782360562003090900000) under FUEL SYSTEMS in REMOVAL & INSTALLATION - SIERRA & SILVERADO - DIESEL article. After replacing fuel injector(s), go to step 9 .
8. Replace fuel pressure regulator. See «FUEL PRESSURE REGULATOR»(ref-158072-S35968660472003090900000) under FUEL SYSTEMS in REMOVAL & INSTALLATION - SIERRA & SILVERADO - DIESEL article. After replacing fuel pressure regulator, go to next step.
9. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to «INTERMITTENTS»(ref-152999-S19570686322003031000000) in TROUBLE SHOOTING - NO CODES - 6.6L SIERRA & SILVERADO - DIESEL article.

1. Turn engine off. Place container on bottom of fuel filter. Open drain valve and drain fuel filter housing. Fill a 0.95 quart (1 liter) container with a sample of fuel. Close drain valve.
2. Obtain a Diesel Fuel Quality Tester (J-38641-B).
3. Fill hydrometer with fuel sample by squeezing hydrometer bulb. Submerse hydrometer tip into sample. Release the bulb, allowing fuel to enter glass tube until fuel completely floats glass bulb inside the tube. Gently spin hydrometer to relieve the surface tension of fuel sample. Read the scale on glass bulb at the point where the top of the fuel sample contacts the scale. By reading this value, the value will give an approximate fuel oil specific gravity. Refer to tool instructions on how to determine API Gravity.
4. If correct fuel is being used and meets diesel No. 1 or No. 2- fuel oil specific gravity requirements, fuel is okay. If not, fuel should be replaced.

1. Before servicing any electrical component, the ignition must off or in LOCK position. All electrical loads must be off, unless instructed otherwise in these procedures. Disconnect battery cables.
2. Drain fuel tank.
3. Remove fuel tank.
4. Cap fuel feed tube and fuel return tube on fuel sender.
5. Connect a piece of hose to the filler tube nipple and plug the opposite end.
6. Submerge fuel tank in water or apply a soapy solution to the outside of tank.
7. Apply 5 psi (35 kPa) of air pressure to the vent hose of the fuel tank. A leak will show up as bubbles.

GLOW PLUG SYSTEM DIAGNOSIS

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

Diagnostic Aids

If glow plug relay or controller is stuck in ON position, check for proper operation of the glow plugs. When glow plugs are commanded ON by scan tool, an internal ECM timer protects glow plugs from damage by cycling them ON for 3 seconds and then OFF for 12 seconds. Most glow plug system failures are covered by DTC P0380. If no DTCs are stored and the engine is hard to start, and White smoke is present during cranking or after engine is started, the most likely cause of failure is faulty glow plugs.

1. Perform Diagnostic System Check - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROL»(ref-158516-S41425574832003100300000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. After performing Diagnostic System Check - Engine Controls, go to next step.
2. Are DTCs P0117, P0118 or P0380 stored as history or current codes? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158516-S25875883752003100300000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If no, go to next step.
3. Turn ignition off. Disconnect all glow plugs. Using a test light connected to battery voltage, probe the spade terminal on each glow plug. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
4. Turn ignition on, with engine off. Ensure glow plugs are still disconnected. Probe each glow plug supply voltage circuit with test light connected to ground. Using scan tool, command glow plugs on. Does each circuit illuminate the test light? If yes, go to next step. If no, go to step 10 .
5. Does test light illuminate all the time for each glow plug terminal, even when glow plugs are not commanded ON? If yes, go to next step. If no, go to step 11 .
6. Disconnect glow plug supply voltage connection from the glow plug relay. Probe each glow plug terminal with a test light connected to ground. Does the test light illuminate for all terminals? If yes, go to next step. If no, go to step 8 .
7. Repair short to voltage on glow plug supply voltage circuit. After repairs, go to step 11 .
8. Replace glow plug relay/controller, located on upper intake manifold. After replacing glow plug relay/controller, go to step 11 .
9. Replace all glow plugs that do not turn ON the test light. After replacing low plug(s), go to step 11 .
10. Repair open in each circuit that does not turn ON the test light. After repairs, go next step.
11. Operate vehicle within the conditions under which system fault was noted. Does the system operate properly? If yes, system is okay. If no, go to step 1 .