Honda Jazz ECU Misfire P0301 P0302 P0303 P0304 — ECU Repair Specialist | The Vehicle Check

Fault codes P0301, P0302, P0303 and P0304 on a Honda Jazz indicate cylinder-specific misfires — and when all four appear together the ECU is almost certainly the cause rather than the ignition or fuel system. The Vehicle Check specialises in Honda Jazz ECU misfire repair, restoring correct injector and ignition timing control across all four cylinders. Nationwide mail-in postal service with drop off at our Enfield office.

P0301–P0304 Explained

Each P030X code identifies a specific cylinder misfire. P0301 = Cylinder 1, P0302 = Cylinder 2, P0303 = Cylinder 3, P0304 = Cylinder 4. When these codes appear and spark plugs, coils and injectors have been checked without resolution — the ECU internal driver circuits are almost certainly the cause. Failed driver transistors produce incorrect or missing firing signals. These codes return immediately after clearing because the transistor fault is permanent.

Why the ECU Causes Misfire Codes

The Honda Jazz ECU contains internal driver circuits — small transistors and MOSFETs — that switch the current required to fire each ignition coil and injector. Over time these degrade. When one fails the coil or injector it controls no longer fires correctly, producing a cylinder-specific misfire code. Replacing the coil, plug or injector makes no difference because the fault is inside the ECU output circuit, not the external components.

Symptoms

  • Rough idle — engine shaking or vibrating at rest
  • Loss of power particularly under acceleration
  • Stalling from cold or when pulling away
  • Misfire on startup — engine runs on 2 or 3 cylinders
  • Engine management warning light on dashboard
  • P0301–P0304 returning immediately after clearing
  • No improvement after replacing spark plugs, coils or injectors

Fault Codes

P0301

Cylinder 1 misfire detected — ECU driver circuit not firing coil on cylinder 1 correctly.

P0302

Cylinder 2 misfire detected — incorrect or missing firing signal to cylinder 2 coil.

P0303

Cylinder 3 misfire detected — ECU driver circuit failure on cylinder 3.

P0304

Cylinder 4 misfire detected — internal ECU fault causing failure to fire cylinder 4.

P0300

Random / multiple cylinder misfire — stored when misfires detected across more than one cylinder.

P0201–P0204

Injector circuit faults — commonly stored alongside misfire codes when ECU injector driver circuits fail.

Models Covered

Honda Jazz Mk1 GD
Honda Jazz Mk2 GE
Honda Jazz Mk3 GG
Honda Jazz 1.2 i-VTEC
Honda Jazz 1.4 i-VTEC
Honda Jazz IMA Hybrid

How Our Service Works

1
Contact us with your full fault code list and Jazz model year. Contact form or call 0203 489 2610.
2
Remove your Honda Jazz ECU and read our how to send your unit guide.
3
Post to: The Vehicle Check, Office 13, 25 Mollison Avenue, Enfield, EN3 7LW.
4
We repair your ECU at component level — replacing failed driver circuits and retesting all cylinder outputs before return.
5
Refit your original ECU. No coding or programming required — your ECU retains all vehicle data.

Don't See What You Need?

Call 0203 489 2610 or email info@thevehiclecheck.co.uk.

Honda Jazz Misfiring on P0301–P0304? Send Your ECU Today.

Contact us first with your details. Post from anywhere in the UK or drop off at our Enfield office. Fast turnaround, warranty included.

Call: 0203 489 2610  |  Email: info@thevehiclecheck.co.uk

Office 13, 25 Mollison Avenue, Enfield, EN3 7LW