OBD codes / P0355
P0355
SeriousIgnition Coil E Primary/Secondary Circuit (Cylinder 5)
A cylinder 5 misfire sends raw fuel into the catalytic converter, and converters die by overheating. Steady light and smooth-enough running: a short, gentle drive to the shop is reasonable. Flashing light: back out of the throttle and treat the repair as urgent — a melted catalyst turns a cheap coil job into an expensive exhaust job.
What this code means
The ECM fires ignition Coil E — cylinder 5's coil — by switching its primary winding, and it monitors that circuit for the expected electrical signature on every spark event. P0355 sets when the circuit reads open or shorted, meaning the fault is electrical: the coil, its connector, or its wiring, as opposed to a worn spark plug that merely sparks weakly while the circuit stays intact. By definition this code only appears on engines with five or more cylinders, and where cylinder 5 physically sits depends entirely on the manufacturer's numbering — on many transverse V6 installations it lands on the rear bank against the firewall, which matters a lot for repair labor. Common causes are a failed coil, a corroded or loose connector, chafed harness wiring, or a blown fuse in the coil feed; a dead ECM coil driver is possible but uncommon. Expect the companion cylinder 5 misfire code, P0305, to be stored alongside it.
Symptoms you might notice
- Persistent misfire on cylinder 5
- Rough idle and vibration through the cabin
- Flashing check-engine light under load
- Unburned-fuel smell from the exhaust
- Loss of power; misfire code P0305 usually accompanies it
What it costs to fix
Typical range: $60–$550 · about ~0.2–3 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Ignition coil (single) | $30–$150 | ~0.2–3 hrs |
| Wiring or connector repair | $5–$50 | ~0.5–2 hrs |
| Spark plugs (while in there) | $20–$100 | ~0.5–1.5 hrs |
The coil itself is a modest part either way — what swings this repair is access. On an inline five- or six-cylinder, coil 5 is on top and labor is minimal (0.2–0.5 hr). On many transverse V6 engines, cylinder 5 is on the rear bank against the firewall and reaching it can require removing the upper intake manifold, pushing labor to 1–3 hours — which is also why shops often suggest doing all three rear plugs and coils while everything is apart.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0355 for my exact vehicle →
Frequently asked
Why is fixing P0355 expensive on some V6 engines?
Not because of the part — a coil is cheap — but because of where cylinder 5 often sits. On many transverse V6 layouts it's on the rear bank, tight against the firewall, and getting a hand on the coil can require removing the upper intake manifold. That turns a 15-minute job into a 1–3 hour one, which is most of the bill.
Is P0355 the coil or the spark plug?
P0355 is a circuit code, so it points at the coil, connector, or wiring — not the plug. A worn plug causes misfires without breaking the circuit. Still, if the rear bank has to come apart to reach the coil, replacing the plugs back there at the same time is smart, because the labor to get at them is the expensive part.
Can I drive with P0355 until my appointment?
Light-duty driving with a steady check-engine light is usually tolerable for a few days, but every mile feeds unburned fuel to the catalytic converter. If the light starts flashing, that's active catalyst damage — minimize driving and move the appointment up.
Which cylinder is number 5 on my engine?
It varies by manufacturer — there's no universal numbering. Some V6s number one bank 1-2-3 and the other 4-5-6; others alternate banks. Your owner's or service literature (or a quick lookup for your specific engine) tells you which physical cylinder is 5, which you'll want to know before doing a swap test.
Seeing P0355 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0355 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0355 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.