P0305 means the ECU counted enough missed combustion events on cylinder 5 (typically over 2% of firings in a 200-rev window) to trip the misfire monitor. Expect rough running and a flashing CEL under load.
DTC/P0305·Jeep
P0305 on Jeep: Causes, Symptoms and Fix Cost
Quick Answer
High SeverityNot safe to driveJeep
P0305 on a Jeep means the ECU counted enough missed combustion events on cylinder 5 (typically over 2% of firings in a 200-rev window) to trip the misfire monitor. Expect rough running and a flashing CEL under load.
Repair cost on Jeep€59 - €3510
What does P0305 mean on a Jeep?
Jeep Grand Cherokee 5.7L HEMI
2005-2018The HEMI runs 16 plugs (two per cylinder). MDS cylinder deactivation applies to cylinders 1, 4, 6 and 7, so on cylinder 5 a persistent misfire is almost always coil, plug, or a collapsed lifter rather than an MDS fault.
What causes P0305 on a Jeep?
Beyond the generic causes listed on the main P0305 page, these are the Jeep-specific patterns we see most often:
Jeep Grand Cherokee 5.7L HEMIOne of the two plugs on cylinder 5 fouled while the other reads fine
Jeep Grand Cherokee 5.7L HEMICollapsed roller lifter wiping the cam lobe (common HEMI failure)
Jeep Grand Cherokee 5.7L HEMIExhaust manifold bolt breakage causing a localised leak that trips the misfire monitor
How to diagnose P0305 on a Jeep with OBD2
Follow these steps to pinpoint the root cause of P0305:
- Read all stored and pending codes. Note fuel trims and any lean/rich codes (P0171, P0174) that could point at a vacuum or injector issue.
- Pull the coil and plug from cylinder 5. Fouled electrode, cracked insulator, or oil in the plug well tells you a lot before you swap anything.
- Swap the cylinder 5 coil with a neighbouring cylinder, clear codes, and drive. If the code moves (e.g. becomes P0303), replace the coil.
- Swap the injector connector or the injector itself with a neighbour if the coil swap didn't move the misfire. A noid light confirms the ECU is pulsing the injector.
- Check live fuel trims and misfire counters with a scan tool. Positive trim on the affected bank points to vacuum leak or weak injector flow.
- Smoke-test the intake if trims are lean. Cracked PCV hoses and split intake boots are common culprits.
- Compression test cylinder 5. More than 15% below the average of the other cylinders points to mechanical trouble. Follow up with a leakdown to isolate valves vs rings.
- After repair, clear codes and complete a misfire monitor drive cycle before declaring victory.
How much does P0305 cost to fix on a Jeep? (EUR)
Estimated repair costs on a Jeep (Jeep parts and labour typically run 30% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0305 on Jeep
These codes commonly cluster with P0305 on Jeep vehicles:
FAQ: P0305 on Jeep
Can I swap the cylinder 5 coil with another cylinder to test it?
Yes, and it's the fastest free test you can do. Move the cylinder 5 coil to cylinder 1 or 3, clear the code, and drive. If P0301 or P0303 pops, the coil is bad. If P0305 comes back, the coil is fine and you're looking at plug, injector, or mechanical.
Will driving with P0305 kill my catalytic converter?
Yes, and quickly. A flashing CEL means raw fuel is hitting a red-hot cat. A sustained misfire can destroy a converter in a few hundred kilometres, turning an €80 coil job into a €600-€1500 cat replacement.
Why does cylinder 5 fail more often than other cylinders?
On most transverse V6s and longitudinal V8s, cylinder 5 sits at the rear of the head where heat soak from the firewall or exhaust is worst. Coils cook faster there. On inline sixes it's simply the second-hottest position. It's not random - rear cylinders live a harder life.
The misfire only happens when the engine is cold. What causes that?
Cold-only misfires usually point to a coil breaking down when secondary resistance is highest, a cracked plug insulator arcing to ground, or an injector that's slow to open cold. Warm-only misfires more often mean a heat-sensitive coil or a compression issue that seals up as the head expands.
I replaced the plug and coil but P0305 came back. What next?
Move to the fuel and vacuum side. Check injector resistance (typically 12-16 ohms on port injection), listen with a mechanic's stethoscope for the click, and smoke-test the intake. If all that's clean, run a compression and leakdown test before spending more on parts.
Looking for the full P0305 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0305 guideSkanyx · Jeep
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