What is the difference between P0350 and P0351?

P0351 names a specific coil circuit, the one for cylinder one, so the search starts at a known place. P0350 is the same category of electrical fault with no cylinder identified, which usually means either that the control unit monitors the coils as a group rather than individually, or that the problem lies in something several coils share such as a supply, a fuse, an earth or an ignition module. In practice P0351 sends you to one coil and P0350 sends you to the wiring.

Does P0350 mean I need new ignition coils?

Not necessarily, and buying a set on the strength of this code alone is a common and avoidable mistake. The code describes a circuit fault, and a circuit includes the supply, the earth, the connectors, the wiring and the control unit driver as well as the coil. On most cars a single genuinely dead coil would have set a numbered code such as P0351 instead. Check the fuse, the supply voltage at the coil connectors and the engine earths before ordering anything.

Can I drive with a P0350 code?

It will usually still drive, but an ignition circuit fault can cut the engine without warning, which is a genuine safety concern at a junction or in traffic. Treat it as a trip to a garage rather than a fault to live with. If the engine has already stalled once, do not take the car onto a motorway or a fast dual carriageway.

Will P0350 fail an MOT?

Yes. An illuminated engine management lamp is a major defect for petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008. There is a second risk with this particular code: if the ignition fault stops the engine running steadily, the emissions test cannot be completed, and an incomplete emissions test is itself a major failure.

Powertrain code · standard

P0350An ignition coil circuit fault, no cylinder named

Standard definition: Ignition Coil Primary/Secondary Circuit/Open

Last updated 27 July 2026

Quick answer

The control unit has found an electrical problem in an ignition coil circuit but has not said which coil. Because it is the shared, unnumbered version of the coil codes, it points more often at something several coils have in common — a supply, a fuse, an earth or an ignition module — than at one dead coil.

How the car works this out

This is an electrical check rather than a combustion one, and that distinction is the whole reason the coil codes exist separately from the misfire codes. The control unit switches each coil's primary winding on to charge it and off to fire it, and while it does so it watches the circuit: how much current the coil draws while charging, and the voltage spike that appears at the moment it is switched off. An open circuit, a short, or no spike at all is a fault it can see without any reference to whether the engine actually ran well. That is why P0350 can be stored on an engine that feels fine, and why you can have a misfire code with no coil code at all, since a coil producing a weak spark is often electrically perfectly healthy.

What you might notice

A misfire, sometimes on several cylinders at once if a shared supply has failed
The engine cutting out completely, or refusing to start, if the whole ignition circuit has gone
A fault that comes and goes with heat, vibration or damp
The engine management lamp on, occasionally with no obvious change in how the car drives

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.

1A failed ignition module or coil pack, on the older designs where several coils share one housing and one driver stageCommon
2A blown fuse or failed relay on the coil supply, which takes out every coil fed from it at oncePossible
How to check: Check the fuse for the ignition circuit before anything else. With the ignition on, there should be battery voltage at the supply pin of each coil connector.
3A corroded, loose or broken earth for the ignition circuitPossible
How to check: Find the engine earth straps and the loom earth points, undo them, clean the mating faces back to bright metal and refit. Voltage drop testing across each earth while the engine cranks will find a bad one that looks fine.
4Chafed or heat-damaged wiring in the coil harness, especially where it crosses the cam cover or runs near the exhaust manifoldPossible
5One coil failing on a car whose control unit does not identify coils individuallyPossible
6Water in the coil connectors after a pressure wash or a deep puddleLess common
7A failed output driver inside the control unitLess common

What to do about it

1Check the ignition fuse and the coil supply voltage first. P0350 with no cylinder named is disproportionately a supply-side problem, and a fuse is the cheapest thing on any car.
2Have the earth points cleaned and checked properly, with voltage drop testing rather than a continuity beep. A poor earth behaves exactly like a failing component and gets a lot of good parts replaced.
3Inspect the harness where it crosses the cylinder head and passes the exhaust manifold. Look for hardened insulation, rubbed-through sections and green corrosion inside the connectors.
4Do not order a full set of coils on the strength of this code alone. It names a circuit, not a component, and on most cars a genuinely dead coil would have brought a numbered code with it.

Can you keep driving?

Only to a garage

An electrical fault in the ignition circuit is unpredictable in a way a worn spark plug is not. It can be intermittent for weeks and then cut the engine dead, which is genuinely unwelcome on a roundabout or pulling out of a junction. Treat it as a job to be done rather than one to live with, and get it looked at rather than commuting on it.

Will it fail an MOT?

There are two separate problems here for the test. The lamp is a major defect in its own right on petrol cars first used from 1 July 2003 and diesels from 1 July 2008, and that defect records 371,859 failures in the DVSA data behind this site. The second is more awkward: an ignition circuit fault that cuts the engine means the emissions test cannot be run at all, and a car that will not hold a steady fast idle for the readings to settle is recorded as failing the emissions check rather than simply not being tested. Turning up with an engine that might die on the ramp is the worst possible way to spend a test slot.

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

What is the difference between P0350 and P0351?: P0351 names a specific coil circuit, the one for cylinder one, so the search starts at a known place. P0350 is the same category of electrical fault with no cylinder identified, which usually means either that the control unit monitors the coils as a group rather than individually, or that the problem lies in something several coils share such as a supply, a fuse, an earth or an ignition module. In practice P0351 sends you to one coil and P0350 sends you to the wiring.
Does P0350 mean I need new ignition coils?: Not necessarily, and buying a set on the strength of this code alone is a common and avoidable mistake. The code describes a circuit fault, and a circuit includes the supply, the earth, the connectors, the wiring and the control unit driver as well as the coil. On most cars a single genuinely dead coil would have set a numbered code such as P0351 instead. Check the fuse, the supply voltage at the coil connectors and the engine earths before ordering anything.
Can I drive with a P0350 code?: It will usually still drive, but an ignition circuit fault can cut the engine without warning, which is a genuine safety concern at a junction or in traffic. Treat it as a trip to a garage rather than a fault to live with. If the engine has already stalled once, do not take the car onto a motorway or a fast dual carriageway.
Will P0350 fail an MOT?: Yes. An illuminated engine management lamp is a major defect for petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008. There is a second risk with this particular code: if the ignition fault stops the engine running steadily, the emissions test cannot be completed, and an incomplete emissions test is itself a major failure.

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