Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

Engine Knocking


1. Defective ECU.
2. Open or shorted fuel injector circuit.
3. Stuck fuel injector.
4. Defective fuel pump main relay.
5. Poor fuel pump ground.
6. Incorrect fuel line pressure.
7. Clogged fuel filter.
8. Open or shorted coolant temperature sensor circuit.
9. Defective coolant temperature sensor.
10. Open or shorted throttle angle sensor circuit.
11. Defective throttle angle sensor.