Possible Causes & Corrections

Check the following items:

• Ensure customer has an actual problem.
• Compare scan tool data at idle with scan tool data list. See PID VALUE CHARTS in PID VALUE CHARTS - SILVERADO & SIERRA article.
• Inspect fuel quality.
• If excessive smoke is present, inspect for a stuck open fuel injector by performing the following procedure:
  1. Remove ignition 1 relay.
  2. Remove glow plugs.
  NOTE: Do not stand in front of glow plug holes while cranking engine.
  3. Crank engine while observing glow plug holes for fuel spray.
  4. Replace fuel injectors for cylinders that spray fuel.
  5. Inspect for contaminated oil or high oil level.
  6. Inspect fuel injectors using Tech 2 scan tool.
• Inspect Engine Coolant Temperature (ECT) sensor. Use scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in coolant sensor circuit or the sensor itself.
• Inspect glow plug system operation.
• Inspect Fuel Rail Pressure (FRP) sensor. Use scan tool to observe FRP with ignition on, and engine off. FRP reading should be 1.1-1.4 MPa. If pressure is not within the specified range, inspect for high resistance in the low reference or 5-volt reference circuits, or a faulty FRP sensor.
• Inspect air cleaner and air intake ducts for restriction.
• Inspect for a restriction in the turbocharger charge air cooler.
• Inspect for a restriction in the intake manifold.
• Inspect the Intake Air Heater (IAH) for proper operation. Use scan tool to command the IAH on and off. See DTC P0540 and P0543. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article.
• Inspect for incorrect basic engine parts such as the camshafts, cylinder heads, pistons, etc.
• Inspect for coolant entering the combustion chamber.