GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 Detonation/Spark Knock

Detonation/Spark Knock

Checks

Action

DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

Preliminary Checks
    • Refer to Important Preliminary Checks Before Starting in Symptoms .
    • Search for bulletins.
    • Check the PCM grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .
    • If the scan tool readings are normal (refer to supporting text of the Powertrain On-Board Diagnostic (OBD) System Check) and there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicle's minimum octane requirements. Refer to Fuel System Specifications . Road test the vehicle and re-evaluate the vehicle's performance.

Fuel System
    • Check for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Check for a restricted fuel filter. Refer to Fuel System Diagnosis .
    •  Check for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check the items that can cause an engine to run lean (long term fuel trim near 24%). For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Ignition System

Check the spark plugs for being the proper heat range. Refer to Spark Plug Visual Diagnosis in Engine Electrical.

Engine Cooling System

Check for obvious overheating problems:

    • Low engine coolant. Refer to Loss of Coolant in Engine Cooling for the type and amount of engine coolant to be used.
    • Restricted air flow to the radiator or restricted coolant flow through the radiator.
    • Inoperative cooling fan. Refer to Fan Clutch Diagnosis in Engine Cooling.

Engine Mechanical

Check for the following engine mechanical problems:

    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical 4.8L, 5.3L, 6.0L.
    • Low cylinder compression. Refer to Engine Compression Test Engine Mechanical 4.8L, 5.3L, 6.0L.
    • Combustion chambers for excessive carbon buildup. Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can.
    • Check for incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Engine/Engine Mechanical.

Additional Checks
    • Check the Park/Neutral Position (PNP) switch operation. Refer to DTC P0705 Trans Range Switch Circuit and DTC P0706 Trans Range Switch Performance .
    • Check the Transmission Torque Converter Clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. Refer to Functional Test in Automatic Transmission 4L60E or Functional Test in Automatic Transmission 4L80E.