Cylinder 6 misfire.
P0306 — also written PO3O6, P 0306, 0306 — is the OBD-II code for cylinder 6 misfire detected. Same code, same fix: this page covers every spelling of it.
Your engine's sixth cylinder isn't firing properly, usually because the spark has died or the fuel isn't burning. It’s a classic headache on the big German straight-sixes and Jaguar V6s common in our neck of the woods.
P0306 is a ignition fault code, typically costing £30–£800 to put right in a UK garage.
What P0306 actually feels like to drive
- The car feels like it's 'juddering' or 'chugging' when you try to overtake on the A9.
- A heavy vibration through the seat and steering wheel when sitting at traffic lights.
- The 'Check Engine' light is flashing (which means it's dumping raw fuel into your catalyst).
- A distinct smell of unburnt petrol coming from the exhaust pipe.
- The car sounds more like a tractor than a smooth six-cylinder at idle.
What causes P0306?
- Spark plug
- Coil
UK vehicles that throw P0306 most often
- BMW 3 Series (E90/F30) 325i/330i N52/N53 engines
- Jaguar XF 3.0 V6 Petrol (2008-2015)
- Ford Mondeo ST220 3.0 V6 (Duratec)
- Vauxhall Insignia 2.8 V6 Turbo (A28NER)
- Audi A6 3.0 TFSI (CREC engine) 2014-2018
- Range Rover Sport 3.0 SC V6 Petrol
How P0306 is fixed
- Plug & coil replacement
The P0306 misdiagnosis that wastes money
I've seen so many lads jump straight to swapping injectors on these big BMW or Jaguar units, costing the customer hundreds in labour and parts. In reality, nine times out of ten it’s either a 'baked' coil pack that’s cracked from heat or, surprisingly often on high-mileage stuff, a simple vacuum leak at the manifold near that rear cylinder. We also get the 'cheap plug' syndrome—people fitting non-resistor plugs they bought off eBay that interfere with the ECU, making it think there's a dead misfire when the engine is actually mechanically sound.
What a UK garage should charge for P0306
For a basic plug and coil swap on a BMW or Ford V6, expect to pay around £120 to £180 at an indie like mine, using Bosch or Delphi parts. If it’s a Jag or a Transverse V6 where we have to pull the whole intake manifold off just to see cylinder 6, you're looking at £350+ in labour alone. A main dealer will easily double these figures, charging you £150 just for the initial 'Hook-up' diagnostic fee before they've even picked up a spanner.
P0306 repair cost in the UK
Most P0306 repairs land between £30–£800 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0306
Before you let a garage talk you into a set of six new injectors, insist they do a 'swap test'. It’s an old-school trick: move the coil from cylinder 6 to cylinder 1, and the spark plug to cylinder 2. Clear the codes and drive it. If the fault code changes to P0301, it’s the coil; if it goes to P0302, it’s the plug. It takes us twenty minutes but can save you a £600 bill for parts you didn't need. Also, ask for Bosch or NGK components—don't let them fit no-name 'white box' parts from the local factor or you'll be back in a month.
Can you drive with P0306?
Drive gently.
Urgency: high.