Test NTC-21: Knocking
- Using scan tool, read DTCs. If no DTCs are present, go to next step. If any DTCs are present, perform appropriate diagnostic test. See DTC & TEST IDENTIFICATION table under DIAGNOSTIC TROUBLE CODE DEFINITIONS.
- Check for correct spark plug application (heat range). See IGNITION SYSTEM in SERVICE & ADJUSTMENT SPECIFICATIONS - CARS article. Check for fuel contamination. Repair as necessary and recheck system operation.