When your 2018 Jeep Wrangler displays the P0305 code, the engine control module has detected repeated misfires in cylinder 5. The 2018 Wrangler (first year of the JL generation) offers the 3.6L Pentastar V6 and the 2.0L turbo four-cylinder. P0305 is valid on the V6 but anomalous on the four-cylinder.
2018 Wrangler Engine Options
The redesigned JL Wrangler launched with the 3.6L Pentastar V6 (285 hp) and added the 2.0L turbo I-4 (270 hp) later in the model year. The V6 has cylinders 1-6; the four-cylinder has only cylinders 1-4.
V6 Diagnosis
On the 3.6L Pentastar, cylinder 5 is on the driver side bank toward the rear. At 2018 mileage levels, spark plug wear is common if not previously replaced. Ignition coil failure, fuel injector issues, and carbon buildup are also possible causes.
Four-Cylinder Models
If your 2018 Wrangler has the 2.0L turbo, P0305 is anomalous. Check for ECM issues and battery condition.
Diagnostic Process
Verify engine type. On V6 models, inspect spark plugs and ignition coils. Check maintenance history. On four-cylinder models, investigate diagnostic errors.