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 visual and physical checks in Diagnosis By Symptom/Preliminary Checks.
^ Transaxle range switch. Be sure Tech 1 scanner indicates drive correct range.

^ If Tech 1 scanner readings are normal (refer to Scan-Tool Diagnostics/Typical Scan Data Values and there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane reading of 92 and re-evaluate vehicle performance.

Check: Exhaust Gas Recirculation (EGR) system for not opening. See Chart C-7 EGR System Check. Refer to C Charts. Chart C-7 EGR System Check
Check: Torque Converter Clutch (TCC) operation for TCC applying too soon. See Chart C-8A TCC Diagnosis. Refer to C Charts. Chart C-8A Torque Converter Clutch (TCC) Diagnosis

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

FUEL SYSTEM
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 a problem.

Lean Condition
A lean condition is present when the long term fuel trim value reads above 150. Refer to "Diagnostic Aids" located in Diagnostic Trouble Codes (DTC) 44. Refer to PCM DTC. Powertrain Controls - ECM/PCM


Rich Condition
A rich condition is present when the long term fuel trim value reads below 110. Refer to DTC 45. Refer to PCM DTC. Powertrain Controls - ECM/PCM

Check: Fuel pressure. Refer to A Charts. Related Tests, Information and Procedures

IGNITION SYSTEM
Check: Spark plugs for proper heat range.

Check: Knock Sensor (KS) system for no retard. See Chart C-5 Knock Sensor System Check. Refer to C Charts. Chart C-5 Electronic Spark Control (ESC) Check


ENGINE MECHANICAL
Check: For excessive oil in the combustion chamber.
- Valve oil seals for leaking.

Check: Combustion chambers for excessive carbon buildup. Remove carbon with top engine cleaner following instructions on can.
Check: Perform a cylinder compression test.
Check: For incorrect basic engine parts such as cam, heads, pistons, etc.

ADDITIONAL CHECKS
Check: Service Bulletin for updates.