Toyota P0301

Cylinder 1 misfire on Toyota — usually coil pack on 1.8 VVT-i / 2.0 D-4D, but on the 1.4 D-4D injector failure is very common.

Toyota P0301 — Cylinder 1 misfire on Toyota — usually coil pack on 1.8 VVT-i / 2.0 D-4D, but on the 1.4 D-4D injector failure is very common. Typical UK independent garage cost: £50–£1200.

What actually causes P0301 on a Toyota

Toyota 1.4 D-4D (1ND-TV) suffers chronic Denso injector failure — copper sealing washers leak, combustion gas blowback carbons up the injector seat, and you get a misfire that sounds like a tractor at idle. Coil packs are a frequent fail on the 1.8 VVT-i petrols at 80,000+ miles.

Toyota engines that log P0301

• 1.4 D-4D (Yaris, Auris, Corolla)
• 1.8 VVT-i (Auris, Corolla, Avensis)
• 2.0 D-4D (Avensis, RAV4, Verso)

How we diagnose P0301 on a Toyota

1. Swap coil pack from cylinder 1 to cylinder 2 — if misfire follows, replace coil
2. On 1.4 D-4D, inspect injector copper washers and seat for blowback (black carbon ring)
3. Compression test if no electrical/injector cause found
4. Live data: check fuel trim and short-term fuel correction per cylinder

The common misdiagnosis to avoid

Replacing a 1.4 D-4D injector without machining the injector seat is a 6-month fix — the carbon damage to the head seat must be addressed at the same time.

Toyota P0301 repair cost in the UK

Expect £50–£1200 including parts and labour at an independent garage. Main-dealer quotes on Toyota are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

On 1.4 D-4D always replace all 4 injector copper washers as a set — it's a £12 part and saves a full repeat job next time.

Codes usually seen alongside P0301 on Toyota

• P0300
• P0302
• P0303
• P0304

Symptoms drivers report with P0301

• Engine 'juddering' like a wet dog when you try to overtake on the A9.
• The car 'kangaroos' at low speeds, especially when the engine is stone cold.
• The EML (Engine Management Light) is flashing at you—that's a 'stop now' warning for your catalytic converter.
• A distinct 'put-put-put' sound from the exhaust pipe at idle.
• Massive loss of power, feels like you're towing a caravan that isn't there.

Repairs that clear P0301

• Replace spark plug
• Swap coil pack
• Injector test
• Compression test

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0301 guide.

Reading P0301 on a Toyota properly

A generic reader will show P0301 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Toyota has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.

Clearing P0301 without fixing it

Erasing the code resets the Toyota's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.

Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0301 is showing on your Toyota, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.