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

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

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Go to Step 14

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to Visual/Physical Checks

If scan tool readings are normal (refer to Engine Scan Tool Data List ) and there are no engine mechanical faults (refer to Engine Knock Diagnosis in Engine General Information), fill fuel tank with a known quality gasoline that has a minimum octane reading of 87 and re-evaluate vehicle performance.

Is detonation present?

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Go to Step 5

Go to Step 14

1. Check the Transaxle Range switch. Refer to DTC P0706 Trans Range Switch Performance .
2. If a problem is found, adjust the Transaxle Range switch as necessary. Refer to 4T60-E Automatic Transaxle On-Vehicle Service .

Was a problem found?

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Go to Step 14

Go to Step 6

1. Check TCC operation. Refer to 4T60-E Automatic Transaxle Diagnosis .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 14

Go to Step 7

1. Check for obvious overheating problems:

•	Low engine coolant. Refer to Diagnosis in Cooling and Radiator.

•	Restricted water flow through radiator. Refer to Diagnosis in Cooling and Radiator.

•	Restricted air flow to radiator. Refer to Diagnosis in Cooling and Radiator.

•	Thermostat stuck closed. Refer to On-Vehicle Service in Cooling and Radiator.

•	Inoperative electric cooling fan circuit(s), refer to Electric Cooling Fan Diagnosis .

•	Correct coolant solution should be a 50/50 mix of approved antifreeze/coolant and water. Refer to Diagnosis in Cooling and Radiator.

•	EGR operation. Go to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient .

2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 14

Go to Step 8

1. Check fuel pressure. Refer to Fuel System Pressure Test .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 14

Go to Step 9

1. Check items that can cause the engine to run lean (long term fuel trim significantly in the positive range). Refer to Diagnostic Aids in DTC P0171 Fuel Trim System Lean .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 14

Go to Step 10

1. Check spark plugs for proper heat range.
2. If incorrect spark plugs are installed, replace spark plugs as necessary. Refer to On-Vehicle Service in Ignition System.

Was a problem found?

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Go to Step 14

Go to Step 11

1. Remove excessive carbon buildup with top engine cleaner. Refer to instructions included with the top engine cleaner.
2. Re-evaluate vehicle performance.

Is detonation still present?

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Go to Step 12

Go to Step 14

1. Perform a cylinder compression check. Refer to Engine Compression Test in Engine General Information.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 14

Go to Step 13

1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no malfunctions have been found, review/inspect the following:

•	Visual/physical inspection. Refer to Visual/Physical Checks .

•	Scan tool data. Go to Engine Scan Tool Data List .

•	Freeze Frame data/Failure Records data.

•	All electrical connections within a suspected circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 14

Review technical bulletins

Operate the vehicle to duplicate conditions present when the original symptom was noted.

Is symptom still present?

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Go to Step 3

System OK