P0305: Cylinder 5 is misfiring
Cylinder 5 Misfire Detected
Cylinder 5 is misfiring. If the light is flashing, stop driving: converter damage happens in minutes. If the light is steady, get it checked the same day.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
What it means
P0305 means the PCM's misfire monitor detected that cylinder 5 is not firing consistently. Cylinder 5 only appears on V6, V8, or inline-6 engines. On V8 engines, cylinder 5 is often toward the rear of one bank, making its coil and injector connectors harder to reach and inspect. The physical location matters because rear cylinders on V8s often suffer more from heat soak and suffer wiring harness damage from exhaust shield contact. The combustion failure risk is the same as any misfire: catalytic converter damage from unburned fuel.
Common causes
- Failed ignition coil on cylinder 5Coil failure is the most common single-cylinder misfire cause. Swap it first.
- Worn spark plug on cylinder 5On V8s where cylinder 5 is at the back of a bank, plug replacement is often deferred and the plug ends up very worn.
- Clogged or failed fuel injector on cylinder 5Injector failure often accompanies P0205 in the code list.
- Compression loss on cylinder 5More common on higher-mileage engines. A compression test will confirm.
What the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Spark plug set
- Ignition coil (one)
- Fuel injector (one)
- Compression or valve repair
Symptoms
- Check engine light flashing or steady
- Noticeable vibration, especially at idle and low speeds
- Power loss when accelerating
- Fuel economy drop
- Possible smell of raw fuel from the exhaust
What to do next
On a V8 or V6, access to cylinder 5 may require removing a coil cover or exhaust heat shield. Swap the coil with a nearby cylinder and road test to see if the misfire moves. If the coil is fine, check the plug. On rear bank cylinders, plugs often get forgotten during routine maintenance and can be the sole cause.
Lewis reads P0305 alongside any misfire codes on other cylinders, so you can see whether it is an isolated failure or spreading. Get Lewis on the App Store or Google Play.
Related codes
FAQ
- Only V8 or V6 engines have cylinder 5, right?
- Cylinder 5 exists on V6, V8, V10, V12, and inline-5 or inline-6 engines. It does not exist on four-cylinder engines.
- Why is cylinder 5 harder to access than cylinder 1?
- On most V8s, cylinder 5 is at the rear of one bank, near the firewall. Spark plug and coil removal often requires ratchet extensions and sometimes removing intake components.
- My truck idles fine with P0305. Can I wait?
- Do not wait. A smooth idle does not mean no misfire. The PCM may be compensating. A flashing light is the urgent signal, but even a steady-light misfire will damage the converter over time.
Check your car's recalls free. No scanner needed.
Lewis checks your car against NHTSA safety recalls by year, make and model. It is free and works before you own a scanner.