Engine Controls - Basic Diagnostic Procedures - 6.6L Diesel: Overview Chevrolet Silverado 1500 HD

Test Description

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

1. 4 - This step tests for an ignition 1 voltage supply to ECM.
2. 6 - This step tests the 12-volt reference circuit to the CKP sensor and CMP sensor. The 12-volt reference circuit for the CKP sensor and CMP sensor is connected internally within the ECM. If the 12-volt reference circuit is shorted to ground, engine will not start and no engine speed will be indicated on scan tool.
3. 8 - If there is fuel in the engine oil, fuel may be leaking from the fuel injector or fuel injection pump into the crankcase.
4. 9 - If fuel system will not even briefly prime to 10 psi and will not start, the check valve in the fuel filter/heater element housing is stuck open. (Scheme 10)
5. 10 - This step determines if fuel system is bleeding down causing a no-start. The fuel pressure will slowly drop to zero psi, but should still be greater than 8 psi, 10 seconds after pressurizing the fuel system.
6. 12 - This step determines if problem is a stuck open or broken fuel injector. If fuel vapors come out of any of the glow plug holes, excessive fuel is being sent into a cylinder and not being distributed to all of the fuel injectors.
7. 13 - The engine will not run without an actual fuel rail pressure more than 1450 psi (10 MPa).
8. 15 - If the no-start condition takes place in cold operating temperatures, 35-40°F (2-4°C) or colder, a glow plug system failure may cause the no-start condition.
9. 17 - In some cases, no compression, possibly with excessive fuel, in a single cylinder can cause a no-start.

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-158516-S41425574832003100300000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. After performing diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Observe the DTC information with a scan tool. Does the scan tool display DTC P0088, P0089, P0090, P0335, P0336, P0340, P0370, P0374, P0380, P0601, P0602, P0603, P0604, P0611, P0612, P1621, P1626, P1631, P1683 or U1800? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158516-S25875883752003100300000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If DTCs are not set, go to next step.
3. Is customer's concern with a fuel smell or fuel leak? If yes, diagnose and repair fuel leak. If no, go to next step.
4. Observe the Actual Fuel Rail Pressure parameter on scan tool. Is pressure within 1.1-1.4 MPa? If yes, go to next step. If no, go to step 18.
5. Observe the Ignition 1 signal parameter on scan tool. Is the ignition 1 signal parameter at battery voltage? If yes, go to next step. If no, go to step 24.
6. Attempt to start engine. Observe Engine Speed parameter with a scan tool while engine is cranking. Is the engine speed parameter more than zero RPM? If yes, go to next step. If no, go to step 19.
7. Test the CKP sensor signal and low reference circuits for high resistance. see scheme 1 Did you find and correct the condition? If yes, go to step 34. If no, go to next step.
8. Inspect for excessive fuel in the engine oil. Did you find and correct the condition? If yes, go to step 34. If no, go to next step.
9. Install Vacuum Gauge (J-44638) to fuel system service port, located on right front side of engine. Attempt to hand prime the fuel manager 30 times or until pressure is 8 psi? If yes, go to next step. If no, go to step 31.
10. Does the pressure measure more than 2 psi for more than 2 minutes? If yes, go to next step. If no, go to step 14.
11. Check engine compression. See «CYLINDER COMPRESSION PRESSURE»(ref-152810-S42366810752003022600000) under MECHANICAL INSPECTION. Did you find and correct the condition? If yes, go to step 34. If no, go to next step.
12. Did any of the cylinders emit any fuel vapor during the engine compression test? If yes, go to step 28. If no, go to next step.
13. Crank engine for 15 seconds. Observe the Actual Fuel Rail Pressure parameter with a scan tool. Is the Actual Fuel Rail Pressure parameter more than 1450 psi (10 MPa)? If yes, go to step 15. If no, go to next step.
14. Reprime the fuel manager to 10 psi. Attempt to start the engine while the prime pressure is still greater than 8 psi. Does the engine start? If yes, go to «FUEL SYSTEM DIAGNOSIS (CAB & CHASSIS)»(ref-152810-S32124860582003022600000) or «FUEL SYSTEM DIAGNOSIS (PICKUP)»(ref-152810-S01617872092003022800000). If no, go to «FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE»(ref-152810-S21775685432003022800000).
15. Observe Glow Plug System Type parameter with a scan tool. Is the glow plug system type Federal? If yes, go to next step. If no, go to step 17.
16. Turn ignition off. Connect a test light to a glow plug harness connector on one side of engine. Turn ignition on, with engine off. Does the test light turn ON and OFF? If yes, go to next step. If no, diagnose glow plug system.
17. Inspect for a plugged air filter, collapsed air intake duct or inoperative fuel heater. If the customer's concern is that the engine will not start when ambient temperatures are less than 35-40°F (2-4°C), check for inoperative fuel heater or restricted exhaust system. Did you find and correct the condition? If yes, go to step 34. If no, see «DIAGNOSTIC AIDS»(ref-152810-S17396650062003022800000).
18. Disconnect fuel rail pressure sensor. Observe the Actual Fuel Rail Pressure parameter on scan tool. Does the actual fuel rail pressure parameter measure more than 175 MPa? If yes, go to step 23. If no, go to step 22.
19. Turn ignition off. Disconnect CKP sensor. CKP sensor is located behind crankshaft pulley. see scheme 3 Turn ignition on, with engine off. Probe the 12-volt reference circuit of the CKP sensor with a DVOM connected to a good ground. see scheme 1 Is voltage more than 10 volts? If yes, go to step 29. If no, go to next step.
20. Turn ignition off. Disconnect CMP sensor. CMP sensor is located on front of engine, below water pump. see scheme 2 Turn ignition on, with engine off. Probe the 12-volt reference circuit of the CMP sensor with a DVOM connected to a good ground. see scheme 1 Is voltage more than 10 volts? If yes, go to step 30. If no, go to next step.
21. Test the 12-volt reference circuit of CKP and CMP sensors for a short to ground. Did you find and correct the condition? If yes, go to step 34. If no, go to step 33.
22. Test the fuel rail pressure sensor signal circuit for a short to ground. Sensor is located on fuel junction block, under A/C compressor. Did you find and correct the condition? If yes, go to step 34. If no, go to step 33.
23. Test the fuel rail pressure sensor circuits for high resistance. Did you find and correct the condition? If yes, go to step 34. If no, go to step 25.
24. Test the ignition 1 voltage circuit of the ECM for a short to ground, a high resistance or an open circuit. Replace fuse, if necessary. Did you find and correct the condition? If yes, go to step 34. If no, go to step 26.
25. Test for an intermittent or for a poor connection at the fuel rail pressure sensor. Did you find and correct the condition? If yes, go to step 34. If no, go to step 32.
26. Clean and tighten the ECM shared ground. Attempt to start engine. Does engine start? If yes, go to step 34. If no, go to next step.
27. Test for an intermittent and for a poor connection at ECM. Did you find and correct the condition? If yes, go to step 34. If no, go to step 33.
28. When fuel injector pressure lines are removed, debris will fall on the fuel injector inlet fitting. Vacuum debris from area to prevent debris from falling in the fuel injector. Replace fuel injectors on affected cylinders. After replacing injector(s), go to step 34.
29. Replace CKP sensor. After replacing sensor, go to step 34.
30. Replace CMP sensor. After replacing sensor, go to step 34.
31. Replace fuel filter/heater element housing. After replacing filter/heater element, go to step 34.
32. Replace fuel rail pressure sensor. After replacing sensor, go to step 34.
33. Replace ECM. After replacing ECM, go to next step.
34. Clear any DTCs with a scan tool. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step 2.
35. Warm engine to normal operating temperature. Observe Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158516-S25875883752003100300000) in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If no DTCs are set, system okay.

Scheme 9

Scheme 10

System Description

If fuel supply system is not delivering enough fuel, driveability could be greatly affected. If air is being drawn into the fuel injection system, a cranks but will not run or a hard start symptom could exist. If fuel supply system is suspected of not delivering enough fuel or drawing air, the following systems should be checked: Any air leaks or restrictions between the fuel injection pump and fuel tank will seriously affect pump output. Insufficient fuel in fuel tank. Any loose fuel component connections. Any hoses and lines that are flattening when engine is running or have kinks that would restrict the flow of fuel.

If fuel supply system is not delivering enough fuel, driveability could be greatly affected. If air is being drawn into the fuel injection system a cranks but will not run, a hard start symptom could exist. If fuel supply system is suspected of not delivering enough fuel or drawing air, the following systems should be checked: Any air leaks or restrictions between fuel injection pump and fuel tank will seriously affect pump output. Insufficient fuel in fuel tank. Any loose fuel component connections. Any hoses and lines that are flattening when engine is running or have kinks that would restrict fuel flow.