First you need to check for malfunction codes if the check engine light comes on .
If after the first time the knocking was solved with adjusting the timing belt then you may have a
out of timed engine , this would knock if the timing was out just one tooth .have this rechecked .
The engine light comes ON when the management system see's a malfunction with in the system .when the engine knocks the management system will trip on the check engine light and store a code , from this code this will be most likely your problem .
A engine compression test should be done if there are no codes relating to the knock , as a cylinder with low compression will give you a diesel knock .
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