P0305 Code: Cylinder 5 Misfire Detected
Cylinder 5 is misfiring. First job: work out which bank it sits on, because that decides what to check.
At a glance
Severity: Moderate
- Meaning
- Cylinder 5 Misfire Detected
- System
- Ignition & Misfire · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $100–$4,000
- DIY difficulty
- Moderate
P0305 means the engine computer has counted enough missing power strokes from cylinder 5 to raise emissions. Cylinder 5 only exists on six-cylinder and larger engines, and where it sits depends entirely on how the manufacturer numbers cylinders. On transverse V6s from GM, Toyota and Nissan, the odd cylinders 1-3-5 are on the rear bank against the firewall, so cylinder 5 is the rear cylinder at the transmission end, hidden under the upper intake plenum. Honda and Ford number one bank at a time, which puts cylinder 5 on the accessible front bank of their V6s. On Ford V8s it is the front cylinder of the driver's-side bank, while GM and Chrysler V8s have it third from the front on the driver's side. Because cylinder 5 always shares a bank with two or three other cylinders, the smartest first move is to check whether it is misfiring alone or whether its bank-mates are counting misses too.
Can I keep driving? With a steady light you can drive gently to a shop, but stay off the highway and don't tow. If the light flashes, stop: raw fuel from one cylinder is enough to overheat the catalytic converter on that bank.
How to read P0305
- P Powertrain
- 0 Generic (SAE)
- 3 Ignition / misfire
- 05 Specific fault
Symptoms
- Rhythmic shake at idle, often felt in the steering wheel on transverse V6s
- Check-engine light on, flashing under hard acceleration
- Misfire counts on cylinders 1 and 3 as well, which points to a bank-wide problem
- Coolant level slowly dropping with a sweet smell at the tailpipe (intake gasket leak)
- Hesitation pulling away from a stop and a drop in gas mileage
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Worn, often original, spark plug on a rear bank that was skipped at the last tune-up because the plenum had to come off
- Failing ignition coil or cracked, carbon-tracked boot on cylinder 5
- Upper plenum or lower intake gasket leaking air, or coolant, into the cylinder 5 runner
- Clogged, dripping or electrically weak cylinder 5 fuel injector
- Bank-wide fault shared with the neighbors: restricted fuel rail, sticking VVT actuator or a plugged catalyst on that bank
- Low compression from a burned exhaust valve, worn rings or a collapsed lifter
- Chafed harness or corroded connector on the rear-bank wiring
Diagnosis step by step
Pin down the layout and the bank
Look up the cylinder diagram for your exact engine and note which bank cylinder 5 belongs to. On GM, Toyota and Nissan V6s it is bank 1 (rear); on Honda and Ford V6s it is bank 2 (front); on Ford V8s it is bank 2 and on GM and Chrysler V8s it is bank 1. You need this because fuel trims and oxygen sensor data are reported per bank.
Tools: OBD-II scanner
Compare misfire counters across the bank
Open the per-cylinder misfire counters and watch them at idle and at 2,000 rpm. If only cylinder 5 counts, the fault is local to that cylinder. If 1, 3 and 5 (or 4, 5 and 6) all count, look at things the bank shares: its fuel rail, its intake gasket, its cam phaser and its catalytic converter. Long-term fuel trim that is lean on one bank only confirms a bank-specific air leak.
Tools: OBD-II scanner
Rule out coolant before taking anything apart
Check the reservoir level cold and look for white, sweet-smelling exhaust at startup. Many V6 intake manifolds carry coolant through their gaskets, and a gasket that has let go on the rear bank often shows up first as a misfire on cylinder 5 or 3 after the engine has sat overnight.
Tools: Flashlight
Reach the coil and plug, then swap within the bank
On a rear-bank cylinder, remove the upper plenum or tilt the engine forward on its mount, then swap coil 5 with coil 1 or 3 on the same bank so you don't have to run wiring across the engine. Clear the code, drive, and see whether the misfire follows the coil. Pull plug 5 while you're there and compare its gap and color with the front-bank plugs.
Tools: Screwdriver, Spark plug socket, OBD-II scanner
Smoke-test the plenum and runner 5
With the plenum reinstalled, push smoke into the intake and watch the plenum-to-manifold joint and the runner 5 area. Plastic plenums warp, and their gaskets often fail at the ends nearest the transmission. A leak there leans out cylinder 5 at idle without affecting the rest of the engine much.
Tools: Smoke machine
Injector balance and compression
Run an injector cut-out test if your scanner supports it and compare the rpm drop for cylinder 5 with the others. If ignition and fuel are fine, take a compression reading on cylinder 5 and one front-bank cylinder. A low reading that stays low with a squirt of oil in the cylinder points to a valve.
Tools: OBD-II scanner, Compression tester
Replace the whole rear bank while you have access
If the plenum is off for any reason, replace all three rear plugs, inspect all three coil boots and fit a new plenum gasket. The labor to get back in there later costs more than the parts.
Tools: Spark plug socket, Torque wrench
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace cylinder 5 ignition coil (more if the plenum must come off) | Yes | $100–$400 |
| Replace spark plugs, V6 full set including plenum removal | Yes | $250–$650 |
| Replace upper plenum or lower intake manifold gaskets | No | $350–$900 |
| Replace cylinder 5 fuel injector | No | $200–$600 |
| Cylinder head or valve repair for low compression (V6) | No | $1,800–$4,000 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Chevrolet
GM's 3.1L and 3.4L pushrod V6s are well known for lower intake manifold gaskets that leak coolant into the cylinders, and the 3.8L's plastic upper plenum can do the same. A rear-bank misfire with unexplained coolant loss on one of these engines should be treated as a gasket job, not a coil job.
Toyota
On Toyota and Lexus 3.0L, 3.3L and 3.5L V6s the rear bank (cylinders 1, 3 and 5) sits under the intake plenum and the cowl. Rear plugs on high-mileage examples are often original because a previous owner only paid for the easy front three. If cylinder 5 misfires and the front plugs look new, assume the rear ones were never done.
Field data
| Chrysler | 15 | Pacifica | |
|---|---|---|---|
| Ford | 9 | F-150 SUPER CREW, F-150 SUPERCAB, Edge | |
| Jeep | 7 | Wrangler Unlimited, Liberty, Wrangler | |
| Honda | 6 | Pilot, Accord, Odyssey | |
| Ram | 6 | 1500 Quad, 1500 | |
| Chevrolet | 5 | ||
| Dodge | 3 | Grand Caravan, Charger | |
| GMC | 3 | Acadia, Savana Cargo 2500, Yukon |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
A stored P0305 with the check-engine light on fails an OBD smog inspection. Because rear-bank repairs on a V6 involve the intake, plan the work well before your inspection date so the readiness monitors have time to complete afterward.
Frequently asked questions
Which bank is cylinder 5 on?
It depends on the manufacturer. GM, Toyota and Nissan V6s put the odd cylinders on bank 1, so cylinder 5 is bank 1. Ford and Honda number one bank first, so cylinder 5 is on bank 2. Ford V8s also put it on bank 2, while GM and Chrysler V8s put it on bank 1. Check a diagram for your engine code before you interpret fuel trim or oxygen sensor data.
Why do P0305, P0303 and P0301 show up together?
Those three cylinders share a bank on GM, Toyota and Nissan V6s. Three misfiring cylinders on one bank rarely mean three bad coils; look for something the bank shares, such as an intake gasket, a fuel rail, a cam phaser or a clogged catalytic converter on that side.
Do I really need to remove the intake to get to cylinder 5?
On most transverse GM, Toyota and Nissan V6s, yes, at least the upper plenum. On Honda and Ford V6s cylinder 5 is on the front bank and takes minutes. On V8 trucks it is a front or middle cylinder and usually reachable with the air intake tube out of the way.
Should I replace only the rear plugs?
If the front three were replaced recently, replacing just the rear three is reasonable, as long as you match the type and gap. If you don't know the history, do all six so the engine has a matched set.