What are the most common causes of P0305?

The most common causes are: Bad ignition coil on cylinder 5; Worn or fouled cylinder 5 spark plug; Clogged or leaking cylinder 5 fuel injector; Vacuum or intake gasket leak near cylinder 5; Low compression in cylinder 5.

How much does it cost to fix P0305?

Typical US independent-shop repair cost for P0305 runs about $100 - $500, depending on the root cause. Common fixes: Replace the cylinder 5 ignition coil (about $100 - $300 at a shop); Replace the spark plugs (about $120 - $400 at a shop); Replace the cylinder 5 fuel injector (about $150 - $500 at a shop).

Will P0305 clear itself?

No, not on its own. P0305 will keep coming back every time the relevant monitor re-runs until the underlying cause is actually repaired - clearing it with a scan tool without fixing what triggered it only delays the light coming back on.

P0305: Cylinder 5 Misfire Detected

P0305 quick answer

P0305 means cylinder 5 is misfiring. The usual fix is the cylinder 5 ignition coil or spark plug - swap the coil to another cylinder to confirm before buying parts.

Severity: Moderate
Can I drive? Short-term, usually yes, if the check-engine light is steady - a single-cylinder misfire rarely strands you.
Typical fix: $100 - $500

Also written as PO305 or P305 or P 0305.

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What P0305 means

P0305 means the engine computer detected a misfire in cylinder 5. It appears on five-cylinder engines and on V6 and V8 engines, and the cause is usually the ignition coil, spark plug, or fuel injector for that one cylinder. Cylinder numbering varies by manufacturer, so confirm where cylinder 5 is on your engine before swapping parts. A flashing check-engine light means the misfire is severe enough to damage the catalytic converter.

Symptoms of P0305

Rough idle and engine shake
Hesitation or stumble when accelerating
Flashing check-engine light during a heavy misfire
Reduced power and fuel economy

Is it safe to drive with P0305?

Short-term, usually yes, if the check-engine light is steady - a single-cylinder misfire rarely strands you. Get it diagnosed soon, though, because unburned fuel from cylinder 5 reaches the catalytic converter every time it misfires. If the light starts flashing, stop driving hard and get it fixed before continuing.

What the P0305 fix costs

Fix	DIY parts	At a shop
Replace the cylinder 5 ignition coil	$25 - $100	$100 - $300
Replace the spark plugs	$20 - $80	$120 - $400
Replace the cylinder 5 fuel injector	$40 - $150	$150 - $500

Ranges are rounded and for the US market only - actual price depends on region, shop labor rates, and the exact make and model.

Parts that commonly fix P0305

Ignition coil - Cause #1 for a single-cylinder misfire - prove it with the coil swap test first
Spark plugs - Cause #2: worn or fouled plugs. Replace as a set, in the heat range your engine specifies
Inline spark tester - Shows whether the coil is delivering spark to that cylinder in seconds
Dielectric grease - A thin coat inside the coil boot stops the arcing and moisture that cause repeat misfires
Compression tester - For when the misfire stays put after coil and plug swaps - rules low compression in or out
OBD-II scanner - Reads and clears codes, and shows live data so you fix the cause rather than the symptom

Most of these open an Amazon search - add your year, make and model, because most of these parts are fitment-specific. A few link straight to the exact tool or part we have verified, because it fits any vehicle.

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What P0305 actually means

P0305 means the engine computer counted misfires in cylinder 5 - it watches crankshaft speed for the tiny slowdown a cylinder causes when it fails to fire, and cylinder 5 kept producing it. You will see this code on five-cylinder engines and on V6 and V8 engines, and where cylinder 5 sits depends entirely on the manufacturer's numbering, so confirm the location before you pull anything. The good news is the same as any single-cylinder misfire: the fault is almost always the coil, the plug, or the injector feeding that one cylinder, and a parts swap tells you which.

How to diagnose P0305 step by step

Step 1: Find cylinder 5 on your specific engine Cylinder numbering is not universal. On many V engines the odd cylinders sit on one bank and the even ones on the other, but some makes number one bank front to back first. Check the firing-order diagram in the service manual or on the intake before you touch a coil, because swapping the wrong one wastes the whole test.
Step 2: Read freeze-frame data and misfire counters Note the RPM, load and engine temperature when the code set. A misfire only at idle leans toward a vacuum leak or injector; one only under load points at ignition. If your scanner shows per-cylinder misfire counts, confirm cylinder 5 is the one climbing and that no other cylinder is close behind.
Step 3: Swap the cylinder 5 coil with a neighbor Move the coil from cylinder 5 to an adjacent cylinder on the same bank, clear the code and drive. If the misfire follows the coil to the new cylinder, replace the coil. If it stays on cylinder 5, the coil is fine and you move on to the plug.
Step 4: Pull and inspect the cylinder 5 spark plug Look for a cracked insulator, heavy carbon, oil fouling, or a gap worn wide. Oil on the threads or the tip suggests a leaking valve cover or tube seal. If the plug looks bad, replace the full set rather than one, since they wear together; if it looks normal, swap it to another cylinder to see if the misfire follows.
Step 5: Check the injector for cylinder 5 With the engine idling, listen to the injector with a mechanic's stethoscope or a long screwdriver - it should click steadily like its neighbors. A silent injector means an electrical or injector fault. Swapping the injector with a neighbor, where access allows, confirms it the same way the coil swap did.
Step 6: Compression-test cylinder 5 if spark and fuel check out With the plug out and the fuel and ignition disabled, crank the engine and compare cylinder 5 to the others. Readings within roughly 10 to 15 percent of each other are healthy. A low cylinder 5 means a mechanical problem such as a burnt valve or worn rings, and no coil or plug will fix it.

The most common P0305 misdiagnosis

The classic P0305 mistake is swapping parts on the wrong cylinder because the numbering was assumed rather than looked up. On V engines cylinder 5 is not always where people expect it, so a coil swap on the wrong bank proves nothing and a new coil goes in the wrong hole.

Tools you need for P0305

OBD2 scanner with misfire data - Per-cylinder misfire counts show whether the coil swap actually moved the problem.
Inline spark tester - Confirms the coil is producing spark before you buy one, in seconds.
Compression tester - The last check before blaming the coil or plug - rules out a mechanical fault in cylinder 5.

Parts you may need for P0305

Ignition coil - The most common cause of a single-cylinder misfire. Match it to your exact engine.
Spark plugs (full set) - Replace as a set with the heat range and gap your engine specifies.
Dielectric grease - A thin film inside the coil boot keeps moisture out and stops it sticking to the plug.

P0305: DIY or pay a shop?

Difficulty: Easy to Moderate. Time: 0.5 - 2 hours. DIY parts: $20 - $150. Shop total: $100 - $450.

A cylinder 5 coil or plug is a straightforward DIY on most engines, and the coil swap test costs nothing but a few minutes. The only thing that pushes it to a shop is location - on some transverse V6 engines cylinder 5 sits on the rear bank under the intake plenum, and that turns a ten-minute job into a two-hour one.

How to stop P0305 coming back

Replace spark plugs on the factory interval. Worn plugs need more voltage to fire, and that extra load is what eventually cracks coils and boots. Changing plugs on schedule protects the coils, and a healthy ignition system keeps unburned fuel out of the catalytic converter. Add this vehicle to ServiceSage and it reminds you when the spark plug interval comes up, so the next misfire never gets the chance to start. Track this maintenance free.