Possible Causes & Corrections

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.

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.
Observe the actual vs. desired fuel rail pressure with a scan tool, with engine running.
Inspect fuel injectors using Tech 2 scan tool.
Inspect Engine Coolant Temperature (ECT) sensor. Use scan tool in order to compare 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 the glow plug system operation.
Inspect Fuel Rail Pressure (FRP) sensor. Use scan tool to observe FRP with engine off. FRP 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 the sensor, or a faulty sensor.
Inspect air cleaner and air intake ducts for restriction.
Inspect for contamination of the Mass Airflow (MAF) sensor.
Inspect for a restriction in the turbocharger charged air cooler.
Inspect for a restriction in the intake manifold.
Perform a cylinder leakage test.
Perform engine compression test. See CYLINDER COMPRESSION PRESSURE under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article.
Inspect for incorrect basic engine parts such as the camshafts, cylinder heads, pistons, piston rings and valves.
Inspect for excessive oil entering the combustion chamber.
Inspect for leaking seals in turbocharger. A slight film on intake side is normal.