P0351 P0xxx · Powertrain (P) High severity
Ignition Coil A Primary / Secondary Circuit Malfunction
The ECU monitors the coil primary circuit for cylinder 1 and sees a fault — open, short, or a coil that does not draw the expected current.
Severity guidance: High — stop driving and diagnose now; risk of further damage
Symptoms you will notice
- Hard misfire on cylinder 1
- Rough running
- Flashing MIL
- Possible no-start on single-coil engines
Common causes
Ordered from most to least likely — start at the top.
- 1 Failed ignition coil
- 2 Open or shorted wiring to the coil
- 3 Corroded connector
- 4 Failed ECU ignition driver
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Swap the coil with another cylinder — if the code follows, replace the coil.
- ✓ Check for battery voltage at the coil connector and a switched earth from the ECU.
- ✓ Scope the primary waveform to check dwell and switching.
- ✓ Inspect the connector for corrosion and pushed-out pins.
Repair options
- Replace the ignition coil
- Repair the wiring or connector
- ECU repair if the driver stage has failed
P0351 — frequently asked questions
Is coil or plug more likely? +
Coils fail more often than plugs on modern engines, but plugs are cheaper — inspect both before ordering.
Do I need to replace all of them? +
If one has failed from age, the rest are close behind. Replacing the set avoids repeat labour.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.