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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS 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 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. NOTE: If there is high resistance in the signal or low reference circuits of the CKP sensor, the Engine Speed parameter on scan tool will display a value more than zero. It will not be an accurate measure of engine speed and can cause an engine cranks, but does not run condition.
  7. Test the CKP sensor signal and low reference circuits for high resistance. See Figure. 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  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)  or FUEL SYSTEM DIAGNOSIS (PICKUP)  . If no, go to FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE .
  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. NOTE: Repeat this procedure on both engine banks. This test may be repeated as many times as necessary.
  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 .
  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 Figure. 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 Figure. 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 Figure. 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 Figure. 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 in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article. If no DTCs are set, system okay.
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