The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P0355.
DTC/P0355·BMW
P0355 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeverityNot safe to driveBMW
P0355 on a BMW means the engine computer saw an electrical fault in the primary or secondary circuit of ignition coil E, which on engines with one coil per cylinder is the coil for cylinder 5. The code only exists on engines with five or more cylinders: five-cylinder engines, inline sixes, V6s, V8s and larger. Most often the coil itself has failed; less often it is the connector, the wiring or the engine computer's driver for that coil.
Typical repair cost, all makes€55 - €1500
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BMW 5 Series 545i / 550i (N62 V8)
2003-2010The port-injected N62 V8 is known for valve stem seals that harden and let oil into the combustion chambers, fouling the spark plugs. An oil-fouled or worn plug raises the voltage the coil must produce, so inspect the cylinder 5 plug whenever the coil is replaced; blue smoke after a long idle points to the seals as the underlying cause.
BMW X5 xDrive50i (N63 twin-turbo V8)
2011-2018The N63 is a direct-injection twin-turbo V8 with both turbochargers inside the V, and fuel injector faults are among its documented problems. An injector fault sets a misfire code (P0305) or an injector circuit code rather than a coil code, while P0355 is an electrical fault in the coil circuit, so with this code stored, test the coil, plug and wiring before looking at the injector.
What causes P0355 on a BMW?
Beyond the generic causes listed on the main P0355 page, these are the patterns noted for BMW models:
BMW 5 Series 545i / 550i (N62 V8)Oil-fouled plug on cylinder 5 from hardened valve stem seals
BMW 5 Series 545i / 550i (N62 V8)Coil failure on cylinder 5
BMW X5 xDrive50i (N63 twin-turbo V8)Coil failure on cylinder 5
BMW X5 xDrive50i (N63 twin-turbo V8)Worn spark plug on cylinder 5
How to diagnose P0355 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0355:
- Read all stored codes and the freeze frame. A cylinder 5 misfire code (P0305) stored alongside P0355 confirms the cylinder is really dropping out, not just logging an electrical glitch.
- Find cylinder 5 in the service data for your engine. Coil E follows the engine's own cylinder numbering, and on V engines that numbering differs from maker to maker.
- Remove the cylinder 5 coil and inspect the boot for cracks, carbon tracks or oil, and the connector for green corrosion, bent or pushed-back pins and a broken locking tab.
- Swap the cylinder 5 coil with the one from cylinder 3, clear the codes and drive. If the fault moves (P0355 becomes P0353), the coil is bad. If P0355 returns, look at the plug, connector and wiring.
- Pull the cylinder 5 spark plug and check the gap, electrode wear and any oil or fuel fouling. A worn plug makes the coil work harder and can kill a new coil quickly.
- Key on, engine off: confirm battery voltage at the coil supply pin against a good ground. While cranking, check that the engine computer is switching the trigger wire with an LED test light or an oscilloscope. Avoid an ordinary bulb test light, which can load the trigger circuit on coils with a built-in igniter.
- Follow the harness towards the engine computer looking for chafing, heat damage or rodent bites, especially where it runs over the back of the engine or close to the exhaust.
- If coil, plug, supply and wiring all pass, the coil driver in the engine computer is the remaining suspect. That needs a workshop with an oscilloscope and the wiring diagram.
How much does P0355 cost to fix on a BMW? (EUR)
Estimated repair costs for P0355 in EUR, compiled across makes. Expect BMW parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to P0355
These codes are often seen alongside P0355 or point to related issues, on any make:
Looking for the full P0355 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0355 guideSkanyx · BMW
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