Which bank is cylinder 5 on?

It depends on the manufacturer, and cylinder five is the position where the two conventions disagree. Where the numbering alternates between banks, cylinder five joins one and three on bank one. Where it runs down one bank before starting the other, cylinder five joins four and six on bank two. On V8s the common split is one to four on bank one and five to eight on bank two, but not universally. Bank one is always defined as the bank containing cylinder one, so look up the numbering for your specific engine rather than assuming.

Can a 4-cylinder engine set a P0305 code?

No. There is no cylinder five to misfire, so if a reader shows P0305 on a four-cylinder car something else is going on. The usual explanations are a misread of a similar-looking code such as P0355, a generic reader mapping a manufacturer-specific code onto the wrong generic definition, or the code having been read from the wrong vehicle. Check the code again with a different tool before spending anything.

Will a P0305 fail an MOT?

Yes. An illuminated engine management lamp is a major defect on petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008, and that defect records 371,859 failures in the DVSA data behind this site. The misfire will also normally raise the hydrocarbon reading beyond the emissions limit, which fails the car separately from the lamp.

Powertrain code · standard

P0305Cylinder 5 is misfiring

Standard definition: Cylinder 5 Misfire Detected

Last updated 27 July 2026

Quick answer

Cylinder five is missing combustion events, which immediately tells you the engine has at least five cylinders. It is also the position the two common numbering conventions disagree about most, so this is the code where people are likeliest to spend an afternoon working on the wrong bank.

How the car works this out

Detection is the same crankshaft-deceleration measurement used for every cylinder, but the arithmetic of where cylinder five sits is not. On a V6 numbered alternately between banks, cylinder five is on bank one along with cylinders one and three. On a V6 numbered down one bank first, cylinder five is on bank two along with four and six. On most V8s the split runs one to four on bank one and five to eight on bank two, which puts cylinder five at the front of the second bank, but some manufacturers number V8s alternately instead, which puts it on bank one. In other words, the cylinder number alone will not tell you the side. Look it up for your engine before anything comes off.

What you might notice

An uneven idle, usually less dramatic on a five, six or eight cylinder engine than the same fault on a small four
Vibration and a change in exhaust note that a driver used to a smooth engine notices immediately
Hesitation and reduced power under acceleration
The engine management lamp on, flashing if the cylinder is fully dead

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1The ignition coil for that cylinderCommon
How to check: Swap with a coil from a cylinder you can reach comfortably, clear the code and drive it. Keep track of which coil went where, because it is easy to lose your place on a six or eight cylinder engine.
2A worn spark plug, particularly on the inline five-cylinder engines where the end cylinder is the least accessible and the most likely to have been skippedCommon
3A blocked, leaking or dead injectorPossible
4Oil in the plug well, or a perished coil bootPossible
5Wiring or connector damage on the harder bank of a V engine, where the loom runs hotter and gets inspected lessPossible
6Low compression in that cylinderLess common
How to check: A compression test, then a leak-down test if it reads low. Worth reaching sooner rather than later on a high-mileage large engine.

What to do about it

1Find out where cylinder five actually is on your engine before removing anything. This is the number the conventions disagree about, and on a V engine the wrong guess means working on the opposite side of the car.
2Note down which bank the car reports other bank-specific codes against, such as P0430 for bank two catalyst efficiency. It is a useful cross-check on which side the manufacturer calls what.
3Swap the coil, then the plug, then the injector, checking after each whether the code follows the part to its new cylinder.
4On an inline five, treat the end cylinder like the awkward cylinder it is and check the plug and coil boot are properly seated rather than assuming the last person who was in there managed it blind.

Can you keep driving?

Only to a garage

A five, six or eight cylinder engine hides a single dead cylinder better than a small four does, which is exactly why people keep driving them. The catalytic converter does not care how smooth the car feels: the fuel from that cylinder is still arriving unburnt, and on a V engine there are two converters to ruin rather than one. Get it looked at rather than living with it.

Will it fail an MOT?

Larger engines get no leniency at the test. The lamp defect is written by date of first use, not by engine size or cylinder count, so a six-cylinder car first used in 2004 is caught by exactly the same rule as a small hatchback. The emissions limits work the same way: the default fast idle figures apply unless the manufacturer's own plate values are lower, and a misfiring cylinder pushes the hydrocarbon reading up regardless of how many other cylinders are behaving.

The light this turns on

Engine management lightThe engine management system has found a fault it cannot correct and has stored a code for it. The car will usually still drive, but an illuminated engine light is an automatic MOT failure on petrol cars first used from 1 July 2003 and diesels from 1 July 2008.

Common questions

Which bank is cylinder 5 on?: It depends on the manufacturer, and cylinder five is the position where the two conventions disagree. Where the numbering alternates between banks, cylinder five joins one and three on bank one. Where it runs down one bank before starting the other, cylinder five joins four and six on bank two. On V8s the common split is one to four on bank one and five to eight on bank two, but not universally. Bank one is always defined as the bank containing cylinder one, so look up the numbering for your specific engine rather than assuming.
Can a 4-cylinder engine set a P0305 code?: No. There is no cylinder five to misfire, so if a reader shows P0305 on a four-cylinder car something else is going on. The usual explanations are a misread of a similar-looking code such as P0355, a generic reader mapping a manufacturer-specific code onto the wrong generic definition, or the code having been read from the wrong vehicle. Check the code again with a different tool before spending anything.
Will a P0305 fail an MOT?: Yes. An illuminated engine management lamp is a major defect on petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008, and that defect records 371,859 failures in the DVSA data behind this site. The misfire will also normally raise the hydrocarbon reading beyond the emissions limit, which fails the car separately from the lamp.

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