GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Lack of Power, Sluggishness, or Sponginess

Checks

Action

DEFINITION: The engine delivers less than expected power. There is little or no increase in speed when partially applying the accelerator pedal.

Preliminary Checks
    • Refer to Symptoms - Engine Controls .
    • Inspect for auxiliary fuel filters. Refer to Fuel Injection Line Routing Diagram for proper fuel tilter locations. Aftermarket fuel filters may restrict fuel flow.
    • Compare the vehicle with a similar unit. Ensure the vehicle has an actual problem.
    • Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List .
    • Remove the air filter and check for dirt, or for air ducts being plugged or leaking. Repair or replace as necessary.
    • Inspect for a proper transmission operation.
    • Inspect the engine oil level and quality.

Sensor Inspection
    • Observe the fuel rail pressure (FRP) sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor exists.
    • Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the 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.

Fuel System Checks
    • Inspect the fuel supply to the fuel injection pump. Refer to Fuel System Diagnosis .
    • Observe the actual vs desired fuel rail pressure with a scan tool, with the engine idling.
    • Start the engine and command the fuel pressure to 160 MPa with a scan tool. If the actual fuel pressure does not reach 160 MPA, go to Fuel System Diagnosis - High Pressure Side .
    • Inspect the engine speed signal circuit for high resistance.
    • Inspect for restricted or plugged fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 .

Exhaust System Checks

Inspect the exhaust system for a possible restriction. Refer to Restricted Exhaust in Engine Exhaust.

Air Intake System Checks
    • Inspect for an air leak or restriction in the air inlet ducts or the intake manifold. Refer to DTC P0234 .
    • Inspect for an air leak in the charge air cooler with a J 46091 Charge Air Cooler Tester.
    • Inspect for a restriction in the charge air cooler.
    • Inspect for a worn or damaged turbo charger turbine wheel, shaft or compressor wheel.
    • Inspect for a skewed mass air flow (MAF) sensor. Refer to Diagnostic Aids in DTC P0101 .

Engine Mechanical Check

Inspect the engine for the following:

    • Low compression
    • Improper valve timing
    • Improper or worn camshaft

Refer to Engine Compression Test in Engine Mechanical.

Additional Checks
    • Inspect the control module grounds for being clean, tight, and in their proper location.
    • Inspect the torque converter clutch (TCC) operation.
    • Inspect the air conditioning system for proper operation. Refer to Diagnostic System Check - HVAC Systems - Automatic or Symptoms - HVAC Systems - Manual in HVAC.
    • Inspect the generator output voltage. Refer to Charging System Test in Engine Electrical.