# P0305: Cylinder 5 Misfire Detected **Verdict:** Drive to a shop this week Ignition and misfire - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $150-$1,500 - **Urgency:** This week - **Most likely:** Spark plug or ignition coil on cylinder 5 - **DIY?:** Steps 1-2 ## Quick answer P0305 means cylinder 5 is misfiring. It only appears on engines with five or more cylinders, such as V6s, V8s and inline fives. The cause is usually the cylinder 5 coil or spark plug, but on many V6 engines cylinder 5 sits on the hard-to-reach back bank, which raises labor cost. ## What does P0305 mean? P0305 exists only on engines with at least five cylinders: inline fives, such as some Volvo, Audi and older Volkswagen engines, plus V6, V8 and larger engines. Where cylinder 5 sits depends on the maker. On Toyota's transverse V6s it is on the rear bank near the firewall, while on Honda V6s it is the middle cylinder of the front bank. GM and Chrysler V8s put it third on the driver's side, and Ford V8s at the front of the driver's side. The engine computer identifies the misfiring cylinder by matching each crankshaft speed dip to its place in the firing order. P0305 sets when cylinder 5 misfires often enough to raise emissions, usually confirmed on two drive cycles, or immediately with a flashing light if the rate could overheat the catalytic converter. On V engines, cylinder 5 belongs to one bank, so its exhaust feeds that bank's converter and oxygen sensors. ## What are the symptoms of P0305? - Check engine light on or flashing - Rough idle and vibration - Hesitation and power loss - Poor fuel economy ## What causes P0305? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Failing cylinder 5 ignition coil** (most common). Coils on individual cylinders fail one at a time from heat and vibration, so a weakening cylinder 5 coil is the leading cause. The misfire often starts under load and gets steadily worse. Swap the coil with a neighbor on the same bank, such as cylinder 3 on GM, Chrysler and Toyota engines, and see whether the code changes. 2. **Worn spark plug** (common). Rear-bank plugs on transverse V6 engines are harder to reach, so they are more likely to be left in well past their interval. A worn electrode needs more voltage and misfires under load. Oil from a leaking valve cover can also foul the plug. Inspect the cylinder 5 plug and compare it with a plug from the other bank. 3. **Clogged or faulty cylinder 5 injector** (less common). If the coil and plug check good, the cylinder 5 injector may be clogged, stuck or electrically dead. A clogged injector leans the cylinder out, mostly at idle, while on direct-injection engines an injector stuck open can wash the cylinder with fuel. A shop tests the pulse, runs a balance test or swaps injectors. 4. **Intake gasket leak near cylinder 5** (rare). V engines usually have gaskets at each intake runner and an upper plenum gasket that is disturbed whenever rear plugs are serviced. A leaking gasket near cylinder 5 lets in unmetered air, so the cylinder runs lean and misfires at idle. Misfires that start right after a plug job point here. A smoke test of the intake finds the leak. 5. **Low compression in cylinder 5** (rare). A burnt valve, collapsed lifter, worn cam lobe or head gasket leak on cylinder 5 causes a steady misfire that new ignition parts will not fix. Lifter and cam lobe wear on some V8 engines can produce this single-cylinder pattern. A compression test, and then a leak-down test, confirms whether a mechanical fault is to blame. ## How do you diagnose P0305? 1. Find cylinder 5 on a diagram for your engine and note whether it is on the front or rear bank. 2. Swap the cylinder 5 coil with a neighbor on the same bank; if the misfire moves, replace the coil. 3. Inspect the plug for wear, cracks or oil; on rear-bank cylinders some intake parts may need to come off. 4. Test or swap the injector if the misfire stays on cylinder 5. 5. Run a compression test if ignition and fuel check good. ## How do you fix P0305, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Replace the cylinder 5 ignition coil | $150-$450 | Higher end applies when the intake plenum must be removed to reach it. | | Replace spark plugs | $200-$550 | V6 and V8 plug jobs cost more, especially with rear-bank access. | | Replace the cylinder 5 fuel injector | $300-$800 | After testing confirms it. | Full price breakdowns: [ignition coil replacement cost](/cost/ignition-coil-replacement), [spark plug replacement cost](/cost/spark-plug-replacement). ## Is it safe to drive with P0305? > **Drive to a shop this week.** With a steady light, drive gently and get it fixed soon. If the light flashes, stop driving to avoid damaging the catalytic converter. ## Will P0305 fail an emissions test? P0305 with the check engine light on will fail any OBD-based emissions test. On V engines the misfire also overloads one bank's catalytic converter, which can later set a catalyst code for that bank, such as P0420 or P0430. Fix the misfire, clear the code, then drive for several days so the readiness monitors can complete. ## After the repair: clearing P0305 If the upper intake was removed to reach cylinder 5, confirm the shop replaced the plenum gaskets and reconnected every vacuum line, since a leak there can cause a new misfire or lean code. Clear the code, then drive normally while watching cylinder 5 misfire counts. A week without the code returning confirms the fix. ## How to prevent P0305 - Replace all spark plugs, including rear-bank plugs, at the same scheduled interval. - Have the shop install new plenum gaskets whenever the upper intake is removed for rear-bank access. - Fix valve cover leaks on both banks before oil reaches the spark plug wells. - Choose quality coils matched to your engine; redoing a rear-bank coil means paying that labor twice. ## Codes often seen with P0305 - [P0300](/codes/p0300): Random/Multiple Cylinder Misfire Detected - [P0304](/codes/p0304): Cylinder 4 Misfire Detected - [P0306](/codes/p0306): Cylinder 6 Misfire Detected - [P0430](/codes/p0430): Catalyst System Efficiency Below Threshold (Bank 2) ## Frequently asked questions ### Why does P0305 cost more to fix on some V6 engines? On some transverse V6 engines, such as Toyota's, cylinder 5 is on the rear bank under the intake. Reaching its coil or plug may require removing the upper intake plenum, which adds labor time and new gaskets. On engines where cylinder 5 is on the front bank, the same job is much cheaper. ### Can a four-cylinder engine set P0305? No, P0305 can only appear on engines with at least five cylinders. If a four-cylinder shows it, the scan tool may be misreading the code or set to the wrong vehicle. Recheck with a different tool, and make sure the correct year, make and engine are selected. ### Should I replace all spark plugs for P0305? Yes, it is best to replace the full set when the plugs are due. Plugs wear evenly, so a worn plug in cylinder 5 means the others are close behind. Doing them all at once also avoids paying for rear-bank access twice if another plug fails soon after. ### Where is cylinder 5? It depends on the engine. On Toyota transverse V6s, cylinder 5 is on the rear bank; on Honda V6s it is the middle of the front bank. GM and Chrysler V8s place it third on the driver's side, Ford V8s at the front of the driver's side, and inline fives at the far end. ### How much does it cost to fix P0305? Most P0305 repairs cost $150 to $450 for a coil and $200 to $550 for a full set of spark plugs at an independent shop. Rear-bank cylinders that need the intake plenum removed land at the higher end. An injector costs $300 to $800, and compression problems cost considerably more. ### Can I fix P0305 myself? If cylinder 5 is on the front bank or an easy-access V8 bank, a coil or plug swap is a reasonable DIY job. Where it sits on the rear bank under the intake plenum, you need gaskets, torque specs and patience, so many owners pay a shop. Injector and compression work belong at a shop. ### Can P0305 cause a P0420 or P0430? It can over time. On V engines, cylinder 5's exhaust goes to one bank's catalytic converter, and unburned fuel from repeated misfires can overheat and damage it. That bank may then set P0420 or P0430. Fix the misfire before replacing any converter, or the new one may be damaged too. ### Why does my V6 misfire on cylinder 5 after a spark plug change? A misfire right after a plug job usually means something was disturbed. Check that the cylinder 5 coil connector is latched and the plug is the correct type and gap. If the intake plenum was removed, its gaskets and vacuum lines may not have sealed, and a smoke test will find it. ### Can I drive with P0305? With a steady light and a mild shake, gentle driving to a shop is usually fine. A flashing light means ease off and get off the road soon, because the cylinder 5 misfire is overheating one bank's catalytic converter. Do not tow or take long trips until the misfire is fixed. ### Will P0305 pass inspection? No, P0305 with the check engine light lit fails an OBD-based emissions inspection. Once it is repaired, the code is cleared and the readiness monitors reset. Drive normally for several days, then confirm with a scan tool that the monitors are complete before returning for the test. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) ## Other ignition and misfire codes - [P0300 Random/Multiple Cylinder Misfire Detected](https://diagxcar.com/codes/p0300) - [P0301 Cylinder 1 Misfire Detected](https://diagxcar.com/codes/p0301) - [P0302 Cylinder 2 Misfire Detected](https://diagxcar.com/codes/p0302) - [P0303 Cylinder 3 Misfire Detected](https://diagxcar.com/codes/p0303) - [P0304 Cylinder 4 Misfire Detected](https://diagxcar.com/codes/p0304) - [P0306 Cylinder 6 Misfire Detected](https://diagxcar.com/codes/p0306) - [P0307 Cylinder 7 Misfire Detected](https://diagxcar.com/codes/p0307) - [P0308 Cylinder 8 Misfire Detected](https://diagxcar.com/codes/p0308) - [P0316 Engine Misfire Detected on Startup (First 1000 Revolutions)](https://diagxcar.com/codes/p0316) - [P0320 Ignition/Distributor Engine Speed Input Circuit](https://diagxcar.com/codes/p0320) ## Symptoms - [Why is my car idling rough?](https://diagxcar.com/symptoms/rough-idle) - [Why does my car hesitate when I accelerate?](https://diagxcar.com/symptoms/car-hesitates-when-accelerating) ## Repair costs - [Ignition coil replacement cost](https://diagxcar.com/cost/ignition-coil-replacement): $150-$400 - [Spark plug replacement cost](https://diagxcar.com/cost/spark-plug-replacement): $120-$450 --- Source page: https://diagxcar.com/codes/p0305 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.