P0351
Ignition Coil A Primary/Secondary Circuit Malfunction
The engine computer is seeing a problem in the ignition coil circuit for cylinder 1. This can stop that cylinder from firing correctly and can cause rough running, misfires, and poor fuel economy.
- SEV
- 4/5
- DRIVE
- CAUTION
- DIY
- $20–$150
- SHOP
- $120–$450
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Bad ignition coil
- Damaged, loose, or corroded coil connector or wiring
- Failed spark plug causing excessive coil load or misfire
Typical repair cost
DIY usually runs $20–$150. Typical shop repair lands around $120–$450, depending on the root cause.
01 / Definition
P0351 sets when the PCM detects an electrical fault in the ignition coil A circuit, usually the coil serving cylinder 1 on many vehicles. The fault may be on the coil primary control side, the secondary output side, or the wiring/connectors between the PCM and the coil. The code often appears with a misfire code if the coil is not firing correctly.
02 / Drive status
With caution. You may be able to drive short distances, but the engine can run rough and may lose power. Continued driving can damage the catalytic converter and worsen the problem.
03 / Symptoms
- Check engine light
- Rough idle
- Engine misfire
- Loss of power
- Poor fuel economy
- Hard starting
- Engine shaking under load
- Possible flashing check engine light
04 / Causes
| 1 | Bad ignition coil | high |
|---|---|---|
| 2 | Damaged, loose, or corroded coil connector or wiring | high |
| 3 | Failed spark plug causing excessive coil load or misfire | medium |
| 4 | PCM driver circuit problem | medium |
| 5 | Water, oil, or corrosion intrusion into the coil well or connector | medium |
| 6 | Blown fuse or power supply issue to the ignition coil | low |
| 7 | Harness short to power or ground | low |
05 / Diagnostic sequence
- 01Check for other codes, especially misfire codes such as P0301 or power supply codes.
- 02Inspect the coil connector and wiring for damage, corrosion, loose pins, or oil contamination.
- 03Remove and inspect the spark plug for wear, fouling, cracks, or incorrect gap.
- 04Swap the coil with another cylinder if the design allows, then see if the fault follows the coil.
- 05Check for battery voltage, ground, and PCM control signal at the coil connector.
- 06Test coil resistance and output only if the vehicle service information provides valid specifications.
- 07Inspect the wiring harness for opens, shorts, and rubbing points between the coil and PCM.
- 08If all wiring and components test good, diagnose the PCM driver circuit or replace the PCM only after full testing.
06 / Repairs
| 1 | Replace the failed ignition coil | $30–$120 |
|---|---|---|
| 2 | Repair or replace damaged wiring or connector terminals | $20–$200 |
| 3 | Replace worn or fouled spark plugs and correct the gap | $15–$80 |
| 4 | Clean or repair oil or water intrusion in the coil area | $20–$150 |
| 5 | Repair PCM control circuit issues or replace PCM if confirmed faulty | $200–$900 |
07 / Related codes
08 / FAQ
What does P0351 usually mean?
It usually means the ignition coil circuit for cylinder 1 has an electrical fault or the coil is not firing correctly.
Can a bad spark plug cause P0351?
Yes. A worn or fouled spark plug can overload the coil or cause misfire symptoms that lead to this code.
Will replacing the coil always fix P0351?
No. Wiring, connectors, spark plugs, and the PCM control circuit can also cause this code.
Is P0351 serious?
Yes. It can cause misfires, power loss, and catalytic converter damage if driven too long.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.