Diagnostic Aids

If DTCs other than P0300-P0304 are set, diagnose those DTCs first. Check the following and repair as necessary:

• Engine overheating.
• Vacuum leaks.
• EGR system for proper operation.
• PCV system for proper operation.
• Malfunctioning fuel injectors. Fuel injector resistance should be 13-16 ohms at 68°F (20°C).
• Fuel pressure.
• Ignition system for proper operation.
• Engine mechanical malfunction.
• Damaged wiring harness.
• Defective crankshaft timing belt pulley.