Detonation/Spark Knock/Pings

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

PRELIMINARY CHECKS
^ Perform the careful visual / physical checks as described at start of "Symptoms".
^ Transaxle range switch. Be sure Tech 1 scan indicates correct range.

NOTICE: If the Diagnostic System Check show no malfunctions and there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane reading of 92 and revaluate vehicle performance.

^ Exhaust Gas Recirculation (EGR) system for not opening. Refer to Diagnostic Charts / C Charts / Chart C-7 EGR System Check. Chart C-7 EGR System Check
^ [1][2]Torque Converter Clutch (TCC) operation, TCC applying too soon. See Diagnostic Charts / C Charts / Charts (C-8a for 4T60E Or C-8c for 3T40). See C Charts. Testing and Inspection

ADDITIONAL CHECKS
^ Service Bulletins for updates.

IGNITION SYSTEM CHECKS
^ Spark plugs for proper heat range.
^ Knock Sensor (KS) system for no retard, see Diagnostic Charts / C Charts / Chart C-5 Knock Sensor (KS) System Check. Chart C-5 Knock Sensor (KS) System Check

ENGINE MECHANICAL CHECKS
^ Check For excessive oil in the combustion chamber.
- Valve oil seals for leaking.
^ Combustion chambers for excessive carbon build-up. Remove carbon with top engine cleaner and follow instructions on can.
^ Combustion chamber pressure by performing a compression test.
^ For incorrect basic engine parts such as cam, heads, pistons, etc.

COOLING SYSTEM CHECKS
^ Check for obvious overheating problems:
- Low engine coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted water flow through radiator.
- Inoperative electric cooling fan circuit, see Diagnostic Charts / C Charts / Chart C-12 Coolant Fan Control Circuit. [1][2]Chart C-12 Coolant Fan Control Circuit
- Correct coolant solution should be a 50 / 50 mix of GM #1052753 anti-freeze coolant (or equivalent) and water.

FUEL SYSTEM CHECKS

NOTICE: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring long term fuel trim will help identify problem.

Lean - Long term fuel trim above 150. Refer to Diagnostic Aids in text from Code 44 Heated Oxygen Sensor (HO2S) Circuit (Lean Exhaust). Refer to Diagnostic Charts / Diagnostic Trouble Code Charts / Code 44 Heated Oxygen Sensor (HO2S) Circuit (Lean Exhaust).Powertrain Controls - ECM/PCM

Rich - Long term fuel trim below 110. Refer to Diagnostic Aids in text from Code 45 Heated Oxygen Sensor (HO2S) Circuit (Rich Exhaust). Refer to Diagnostic Charts / Diagnostic Trouble Code Charts / Code 45 Heated Oxygen Sensor (HO2S) Circuit (Rich Exhaust). Powertrain Controls - ECM/PCM

^ Check fuel pressure, use CHART A-7. Refer to Diagnostic Charts / A Charts / Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures