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

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

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

Did you find a bulletin that addresses the symptom?

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Go to Step 14

Go to Step 3

Perform the careful visual/physical checks as described at the start of Symptoms section.

Did you perform the visual/physical check?

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Go to Step 4

Go to Important Preliminary Checks

Refer to Engine Scan Tool Data List

If the scan tool readings are normal, and there are no engine mechanical malfunctions, fill fuel tank with a known quality gasoline that has a minimum octane reading of 92, and re-evaluate the vehicle's performance.

Is the detonation present?

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Go to Step 5

Go to Step 14

1. Check for obvious overheating problems:

•	Low engine coolant

•	Restricted air flow to the radiator, or restricted water flow through the radiator

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

•	The correct coolant solution should be a 50/50 mix of approved antifreeze/coolant and water. Refer to Engine Cooling.

2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 14

Go to Step 6

1. Check the fuel pressure. Refer to Fuel System Diagnosis .
2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 14

Go to Step 7

1. Check the items that can cause an engine to run lean. For a lean condition, refer to DTC P0171 Fuel Trim System Lean for diagnosis.
2. If a problem is found, repair as necessary.

Was a repair necessary?

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Go to Step 14

Go to Step 8

1. Check the spark plugs for the proper heat range. Refer to Ignition System .
2. If incorrect spark plugs are installed, replace the spark plugs as necessary.

Did any spark plugs require replacement?

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Go to Step 14

Go to Step 9

1. Remove any excessive carbon buildup with a top engine cleaner. Refer to the instructions on top of the engine cleaner can.
2. Re-evaluate the vehicle performance.

Is the detonation still present?

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Go to Step 10

Go to Step 14

1. Check the Knock Sensor (KS) system for proper operation. Refer to Knock Sensor (KS) System Diagnosis for diagnosis.
2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 14

Go to Step 11

1. Check for an engine mechanical problem. Perform a cylinder compression check (refer to Engine section).
2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 14

Go to Step 12

1. Check the intake valves for valve deposits.
2. If deposits are present, remove the deposits as necessary.

Were there any deposits on the intake valves?

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Go to Step 14

Go to Step 13

1. Review all of the diagnostic procedures within this table.
2. If all of the procedures have been completed and no malfunctions are present, visually/physically inspect the following items:

•	The scan tool data

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

3. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 14

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Operate vehicle within the conditions under which the original symptom was recorded.

Does the system now operate properly?

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System OK

Go to Step 2