Error code P0303 on Nissan: misfire in cylinder 3

If on your dashboard Nissan the indicator came on Check Engineand the scanner showed an error P0303, this is a signal of problems with misfire in the third cylinder. This code doesn't just interfere with a comfortable ride - it can lead to serious engine damage if ignored for too long. Unlike general fuel system errors (e.g. P0300), P0303 clearly indicates a specific cylinder, which narrows the scope of troubleshooting.

Owners Nissan Qashqai, X-Trail, Almera and other models often encounter this problem, especially on runs beyond 100,000 km. The reasons may lie in small things (for example, worn-out spark plugs) or in serious problems (compression or ECU problems). In this article we will analyze all possible reasons, diagnostic and repair methods - from simple to complex. And if you are not confident in your abilities, we will tell you when exactly you should go to the service station.

What does P0303 mean on Nissan?

Code P0303 stands for “Misfire in cylinder No. 3”. This means that the engine control unit (ECU) recorded abnormal combustion of the air-fuel mixture in the third cylinder. Unlike random omissions (P0300), here the problem is localized, which simplifies diagnosis.

How does this manifest itself in practice? The engine starts "triple" - vibrate at idle, lose power during acceleration, and sometimes even stall. On some models Nissan (For example, Juice or Note) the error may be accompanied by popping sounds in the exhaust system or the smell of gasoline due to unburnt fuel. It is important to understand that Driving for a long time with misfires leads to overheating of the catalyst and its failure - and this is an expensive repair..

Modern Nissan (For example, Ariya or Leaf with hybrid systems) can respond to P0303 switching to emergency mode, limiting speed to 3000 rpm. This is protection from further damage, but also a signal for immediate action.

The main causes of error P0303

Misfires in the third cylinder rarely occur “just like that.” Most often, one of the following components is to blame:

• 🔥 Spark plugs or coils - wear, cracks on the insulator, incorrect clearance or oil deposits.
• ⚡ High voltage wires — breakdowns, oxidation of contacts or wire breakage (relevant for older models Nissan with distributor).
• 💨 Injectors - clogging, leakage or failure (especially on engines with direct injection).
• 🔧 Compression in cylinder - worn piston rings, burnt valve or damage to the cylinder head.
• 🖥️ Electronic faults - malfunctions ECU, crankshaft position sensors (CKP) or camshaft (CMP).
• ⛽ Fuel system - low pressure in the rail, low-quality gasoline or clogged fuel filter.

In practice 70% of cases errors P0303 connected to spark plugs, coils or wires. But don’t rush to change them at random! For example, on Nissan X-Trail T31 with engine MR20DE A common problem is cracks in the ignition coils, and on Almera N16 — wear of high-voltage wires. Diagnostics must be comprehensive.

⚠️ Attention: If the error P0303 accompanied by code P0300 (multiple omissions), the problem may be general source - for example, a faulty oxygen sensor or air leaks. In this case, check the system as a whole, and not just the 3rd cylinder.

How to diagnose misfires in cylinder 3?

To pinpoint the cause P0303, follow this algorithm:

1. Count all errors. Besides P0303 there may be codes for oxygen sensors (P0130-P0167), injectors (P0200-P0204) or ignition system (P0351-P0354).
2. Check the spark plugs. Remove the spark plug from the 3rd cylinder and inspect it:
   • 🔴 Black soot - rich mixture or oil zhor.
   • ⚪ White soot - lean mixture or overheating.
   • 🟠 Cracks on the insulator - breakdown, replacement required.

Swap the ignition coils. If after moving the coil from the 3rd cylinder to the 1st cylinder the error changes to P0301, the coil is at fault.

Measure the compression. Normal for most Nissan — 12-14 bar. The difference between the cylinders should not exceed 1 bar.

Check the injectors. By ear (clicks during operation) or using a diagnostic scanner (parameter Injector Balance).

For in-depth diagnostics you will need oscilloscope (checking sensor signals) or compression gauge. If there are no such tools, contact a service station with equipment for Nissan Consult.

Step-by-step instructions: how to fix P0303 yourself

Once you have determined the cause, you can begin repairs. Let's consider most common scenarios and ways to eliminate them.

1. Replacing spark plugs

Candles are the first candidate for testing. On Nissan with engines HR16DE, MR20DE or QR25DE recommended replacement interval - 30,000–50,000 km (or once every 2 years). Use only original spark plugs or analogues with the same parameters:

• 🔧 Gap — 0.8–1.1 mm (check for your model).
• 🔥 Heat number - for the majority Nissan fits NGK IFR6T11 or Denso FK16HR11.

Instructions:

1. Remove the ignition coils (disconnect the connector and unscrew the bolts).
2. Unscrew the spark plug from the 3rd cylinder using a spark plug wrench. 16 mm.
3. Install a new spark plug, having first applied to the thread anti-seize paste.
4. Tighten with torque 20–25 Nm (do not overtighten!).

2. Checking and replacing the ignition coil

Coils on Nissan often fail due to overheating or moisture. Symptoms:

• 🔌 Cracks on the body.
• 💥 Spark breakdown to ground (visible in the dark).
• 📉 Power loss in wet weather.

How to replace:

1. Disconnect the negative battery terminal.
2. Remove the connector from the coil of the 3rd cylinder.
3. Unscrew the fastening bolt (10 mm) and remove the coil.
4. Install a new one (original - Nissan 22448-4M015 or analogues Bosch, Beru).

⚠️ Attention: After replacing coils or spark plugs be sure to clear errors scanner! Otherwise ECU may continue to “see” gaps due to stored data.

3. Cleaning or replacing injectors

If the injector of the 3rd cylinder is clogged or leaking, it needs to be cleaned or replaced. For flushing, use special liquids (for example, Liqui Moly JetClean) or an ultrasonic bath. In case of severe wear - only replacement.

Signs of a faulty injector:

• 🛢️ Gasoline leaks on the ramp.
• 🔥 Detonation during acceleration.
• 📊 Bugs P0203 (injector circuit break) or P0171 (lean mixture).

When is specialist help needed?

Not all faults causing P0303, you can fix it yourself. Contact the service station in the following cases:

Symptom	Possible reason	Recommendation
Low compression (<10 bar)	Worn piston rings, burnt valve	Engine disassembly, replacement of rings/valves
Sensor errors CKP/CMP (P0335, P0340)	Faulty sensors or timing belt	Diagnostics with an oscilloscope, replacement of sensors
Oil in spark plug wells	Worn valve seals or cylinder head gaskets	Replacing seals, checking tightness
The error appears after replacing spark plugs/coils	Incorrect installation, defective parts	Repeated diagnostics, replacement with the original

For example, if on Nissan Pathfinder with engine VQ40DE error P0303 accompanied by white smoke from the exhaust pipe, this may indicate cylinder head gasket failure — here you can’t do without disassembling the engine.

Another difficult case - ECU malfunction. If all mechanical components are in order, but the error does not reset, it may be necessary to flashing or replacing the control unit. This is relevant for Nissan Juke with the system Direct Adaptive Shift Controlwhere are the failures ECU can simulate misfires.

Preventing error P0303 on Nissan

To avoid future misfires, follow these tips:

• 🔧 Change spark plugs and coils regularly. Even if they are “still working”, wear may only appear under load.
• ⛽ Refuel at proven gas stations. Bad gasoline clogs the injectors and leads to carbon deposits on the valves.
• 🔥 Monitor the condition of the air filter. A clogged filter causes a lean mixture and misfires.
• 💨 Check compression every 100,000 km. Early diagnosis of engine wear will save money on repairs.
• 🖥️ Update the ECU firmware. On some Nissan (For example, Ariya) ignition errors are eliminated by updating the software.

Pay special attention winter operation. Cold starts at low temperatures increase the load on the ignition system. If your Nissan It doesn't start well in the morning, this is the first call to check the spark plugs and coils.

What happens if you ignore P0303?

Long-term driving with misfires leads to:

- Overheating and destruction of the catalyst (replacement cost - from 50 000 ₽).

- Increased fuel consumption (up to +30%).

- Wear of piston rings and cylinders due to uneven load.

- In extreme cases - to water hammer (if unburnt fuel gets into the oil).

FAQ: Frequently asked questions about error P0303

Is it possible to drive with P0303?

Short term - yes, but not recommended. Long-term driving with misfires leads to catalyst overheating and increased engine wear. If the error appears for the first time, you can drive to your home or service station, but do not put off repairs for long.

How much does it cost to fix P0303 at a service station?

The cost depends on the reason:

• 🔧 Replacing spark plugs - from 1 500 ₽ (with work).
• ⚡ Replacement coil - from 3 000 ₽ (original) + work.
• 💨 Cleaning injectors - from 5 000 ₽.
• 🔧 Engine repair (compression, valves) - from 20 000 ₽.

Why does P0303 only appear when cold?

This is a typical sign ignition coil malfunction or air leak. At low temperatures, cracks in the coil widen and rubber seals lose elasticity, leading to leaks. Check coils and vacuum hoses.

Could P0303 be due to bad gas?

Yes, poor quality fuel causes detonation and carbon deposits on the spark plugs, which leads to misfires. If the error appears after refueling, try:

1. Add high-quality gasoline (for example, AI-98).
2. Add injector cleaner to the tank (Liqui Moly, Hi-Gear).
3. Drive by 50–100 km at high speeds for self-cleaning.

How to reset error P0303 without a scanner?

You can reset the error by disconnecting the battery at 10–15 minutes (remove the negative terminal). However, this will not eliminate the cause! If misfires remain, the error will return. To completely reset adaptations ECU It's better to use a scanner (for example, ELM327).