OBD-II trouble code
P0305: Cylinder 5 Misfire Detected
A misfire isolated to cylinder 5. Unlike the higher-numbered misfire codes, this one is possible on a five-cylinder engine — and on a V6 it is the cylinder where the two common numbering conventions disagree about which bank it lives on.
Quick facts
- System
- Powertrain
- Category
- Ignition and Misfire
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $50 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0305 mean?
P0305 tells you a cylinder is failing to burn its charge properly and that the engine control module (ECM) has pinned it to cylinder number 5 specifically. That is already most of the diagnostic work done for you — a single-cylinder code means the cause is something that belongs to one cylinder rather than something the whole engine shares.
Cylinder 5 has a quirk none of the other misfire codes share. It is the highest cylinder number a five-cylinder engine can have, so P0305 is a live possibility on the inline-five engines used by Volvo, Audi, Volkswagen and a handful of Fords — and on those, cylinder 5 is the rearmost cylinder in the block. Every misfire code above this one is off the table for a five-cylinder owner. If you drive one of these engines, P0305 is your last-cylinder code, and a five-cylinder running on four has an unmistakable lopsided idle beat that owners often describe before they ever read the code.
On a V6 the picture is genuinely ambiguous and this is where people waste an afternoon. Manufacturers do not agree on how to number cylinders across banks. One widespread convention alternates the numbers between banks, which puts the odd cylinders — including 5 — on the same bank as cylinder 1. Another widespread convention numbers one bank straight through before starting the other, which puts 4, 5 and 6 together on the second bank. Cylinder 5 falls on opposite sides of the engine depending on which convention your manufacturer used, so unlike cylinder 6 there is no safe default guess. Confirm the layout for your specific engine before you take anything apart, because guessing wrong here means pulling the wrong plenum.
A flashing check engine light means the misfire is happening right now and raw fuel is being dumped into the catalytic converter, which can destroy it in minutes rather than months. Stop driving. A steady light means the misfire is present but not currently at damaging levels — drive gently and directly to a shop.
Common causes
- Failing ignition coil on cylinder 5
- Worn, fouled, or incorrectly gapped spark plug in cylinder 5
- Clogged, stuck, or electrically failed injector on cylinder 5
- Low compression in cylinder 5 from a burned exhaust valve, worn rings, or a head gasket breach
- Carbon deposits on the cylinder 5 intake valve, common on direct-injection engines
- Vacuum leak at the cylinder 5 intake runner or its injector seal
- Damaged plug boot or coil connector allowing spark to track to ground
- Broken valve spring or a collapsed lifter on that cylinder
Symptoms
- Check engine light on, or flashing during an active misfire
- Uneven idle with a distinct beat, especially pronounced on a five-cylinder engine
- Hesitation and a hole in power under acceleration
- Raw fuel smell at the tailpipe
- Fuel economy noticeably worse than usual
- Vibration felt through the steering wheel or seat at idle
- Failed emissions test even when the car feels acceptable to drive
Diagnostic steps
- 1.Establish your engine's numbering convention first. On a V6, find out whether cylinder 5 is on the front bank or the rear bank for your specific engine before removing anything — the two common conventions put it on opposite sides.
- 2.Check whether other misfire codes are stored. Several cylinders on one bank point at a shared cause such as fuel supply or a plenum-side vacuum leak rather than a single failed part.
- 3.Pull the cylinder 5 spark plug and read it against the others. Oil fouling, fuel washing, and a cracked insulator each tell a different story.
- 4.Swap the cylinder 5 coil with an adjacent cylinder's coil, clear the codes, and drive. If the misfire code moves to the cylinder you swapped into, the coil is the fault.
- 5.Repeat the same swap logic with the spark plug if the coil test comes back clean.
- 6.Check injector resistance against the other injectors and listen for it clicking with a stethoscope or a long screwdriver.
- 7.If ignition and fuel both test good, run a compression test on cylinder 5, then a leak-down test if compression is low, to distinguish valves from rings.
- 8.On a direct-injection engine with high mileage and no electrical or fuel fault, inspect the intake valve for carbon buildup before condemning internals.
Repair cost
$50 – $1,500
A spark plug is $10 to $30 with 15 to 30 minutes of labor if it is reachable. An ignition coil runs $40 to $200 plus brief labor. An injector is $100 to $400 plus one to three hours. Because cylinder 5's bank placement varies by manufacturer, get the location confirmed before accepting a quote — the same job can be a 20-minute plug change or a plenum removal depending on which side it lands on. Compression repairs start around $1,000.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with ignition coil replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.