When your 2018 Jeep Wrangler displays the P0304 code, the engine control module has detected recurring misfires in cylinder 4. As the first year of the JL generation, the 2018 Wrangler introduced new engine options alongside the proven V6, requiring updated diagnostic understanding.
Understanding P0304 in the 2018 Wrangler
The 2018 JL Wrangler introduced both the 3.6L Pentastar V6 and the new 2.0L turbocharged four-cylinder option. Cylinder 4 location varies—on the inline-four it's at the rear, on the V6 it's on the rear bank. As potentially higher-mileage vehicles, 2018 models may show age-related wear patterns.
First-Year JL Considerations
The 2018 model year marked a significant redesign. First-year production sometimes reveals unexpected issues. Monitor for technical service bulletins addressing 2018-specific concerns. Standard age-related ignition wear compounds any first-year considerations.
Diagnostic Approach
Identify your engine type. Review maintenance history noting mileage context. Retrieve all codes and freeze frame data. Inspect for both environmental damage and age-related wear. Test ignition coil output and spark plug condition.
Repair Solutions
Replace spark plugs with Jeep-specified components—if original, replacement is due regardless of appearance. Address connector corrosion from years of exposure. Replace degraded ignition coils. Consider comprehensive ignition service if maintenance history is incomplete.