Checks
| Action
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Definition: A mild to severe ping which is usually worse upon acceleration.
The engine makes sharp metallic knocks which change with the throttle opening.
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Preliminary Checks
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| • | Make sure the vehicle has an actual problem. |
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Cooling System Checks
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| • | Check for obvious overheating problems. Refer to Engine Mechanical. |
| • | Check for a low engine coolant level. |
| • | Check for a loose water pump belt. |
| • | Check for restricted air flow through the radiator, or restricted
coolant flow. |
| • | Check for proper operation or incorrect thermostat. |
| • | Check for a correct coolant solution. The solution should be a
50/50 mix of anti-freeze and water. |
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Sensor Check
| Check the engine coolant temperature (ECT) sensor. Use the scan tool in order
to compare the engine coolant temperature with the ambient air temperature
on a cold engine. If the coolant temperature reading is more than 5°
greater or less than the ambient air temperature on a cold engine, check
for a high resistance in the coolant sensor circuit or the sensor itself.
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Fuel System Checks
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Important: The most likely cause of a fuel related knock is a stuck closed injector
(sound is similar to a engine mechanical knock).
| • | The scan tool can be used to cut out a specific cylinder to determine
what cylinder or cylinders are affected. It may be difficult to determine
the exact cylinder the knock is coming from because cutting out a cylinder
at idle will affect the fuel charge for the nozzle next in the firing order
(both nozzles should be checked). A suspected injector can be swapped to
another cylinder to see if the knock travels with it. Refer to
Injection Nozzle(s) Diagnosis
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Engine Mechanical Checks
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| • | Check for incorrect basic engine parts such as the cam, the heads,
the pistons, etc. |
| • | Check for any excessive oil entering the combustion chamber. |
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Additional Checks
| Check the Service Bulletins for control module software updates.
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