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, 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.
2. If a problem is found, adjust the Transaxle Range switch as necessary. Refer to Transaxle Park Neutral Position (PNP) Switch/Transaxle Range Switch Adjustment in the 4T60-E Transmission/Transaxle Section.

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 Cooling System Diagnosis.

•	Restricted water flow through radiator. Refer to Cooling System Diagnosis.

•	Restricted air flow to radiator. Refer to Cooling System Diagnosis.

•	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 Cooling System Diagnosis.

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

1. 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. Go 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 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.
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. Go 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.

1. 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