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
1. Perform careful visual and physical checks as described in preliminary checks. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnosis by Symptom / Preliminary Checks. Testing and Inspection
2. Transaxle range switch. Be sure Tech 1 scan indicates correct range.

NOTE: If Tech 1 scan tool readings are normal, refer to Computers and Controls / System Diagnosis / Flow of Diagnosis / Diagnostic System Check.
And if 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.

3. Check the Exhaust Gas Recirculation (EGR) system for not opening. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart C-7. Chart C-7 EGR System Check
4 Check the [1][2]Torque Converter Clutch (TCC) operation, TCC applying too soon. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart C-8A. Chart C-8A Torque Converter Clutch (TCC) Diagnosis

ADDITIONAL CHECKS
Check service bulletins for updates.

IGNITION SYSTEM
1. Check the spark plugs for proper heat range.
2. Check the Knock Sensor (KS) system for no retard, refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart C-5. Chart C-5 Knock Sensor (KS) System Check

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

COOLING SYSTEM
1. 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, refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart C-12. 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

NOTE: 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 Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Code 44. Powertrain Controls - ECM/PCM
^ RICH - Long term fuel trim below 110. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Code 45. Powertrain Controls - ECM/PCM

1. Check the fuel pressure, refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart A-7. Related Tests, Information and Procedures