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:
- Compare vehicle with a similar unit. Ensure vehicle 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.
- Remove air filter and check for dirt. Check for plugged or leaking air ducts. Repair or replace as necessary.
- Inspect for a proper transmission operation.
- Inspect fuel quality.
- Inspect engine oil level and quality.
- Observe Fuel Rail Pressure (FRP) sensor and fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If command is high, a fuel pressure or sensor problem exists.
- Inspect Crankshaft Position (CKP) sensor reluctor wheel. Remove CKP sensor and attempt to move the reluctor wheel front to back or side-to-side with a probe. If there is any movement, the reluctor wheel retaining bolts are loose.
- Inspect fuel supply to the fuel injection pump. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article.
- Observe the actual vs desired fuel rail pressure with a scan tool, with engine idling.
- Inspect engine speed signal circuit for high resistance.
- Inspect for restricted or plugged fuel injectors. Perform Fuel Injector Balance Test using a Tech 2 scan tool.
- Inspect exhaust system for a possible restriction. See RESTRICTED EXHAUST .
- Inspect for an air leak or restriction in air inlet ducts or intake manifold.
- Inspect for an air leak or restriction in the charge air cooler using a Charge Air Cooler Tester (J-46091).
- Inspect for a worn or damaged turbocharger turbine wheel, shaft or compressor wheel.
- Inspect for a skewed Mass Airflow (MAF) sensor. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article.
- Check low compression. See CYLINDER COMPRESSION PRESSURE under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article.
- Improper valve timing.
- Improper or worn camshaft.
- Inspect control module grounds for being clean, tight, and in their proper location.
- Inspect Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.
- Inspect air conditioning system for proper operation. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
- Inspect generator output voltage.