Ignition Coil A Primary/Secondary Circuit Malfunction
P0351 indicates a malfunction in the primary or secondary circuit of ignition coil A, which is responsible for generating the spark needed to ignite the fuel mixture. This code sets when the PCM detects an electrical problem in the coil's control circuit, such as a short, open, or connection issue.
What You Might Notice
- Check Engine Light (MIL) illumination
- Engine misfire, particularly on cylinder 1
- Rough idle or hesitation during acceleration
- Reduced fuel economy
- Engine may run but with reduced power
Most Common Causes
- 1
Faulty ignition coil (COP)
The coil pack itself has failed electrically, preventing proper spark generation. This is the most common cause of P0351.
- 2
Loose or corroded coil connector
A loose, corroded, or damaged connector at the coil or PCM side breaks the electrical circuit, causing signal loss.
- 3
Short or open in driver circuit wiring
Damaged, pinched, or shorted wiring between the PCM and ignition coil prevents proper voltage/ground connection.
- 4
Faulty Powertrain Control Module (PCM)
The PCM's coil driver circuit has failed, preventing it from commanding the coil properly.
How to Diagnose It
- 1
Check Faulty ignition coil (COP) — The coil pack itself has failed electrically, preventing proper spark generation. This is the most common cause of P0351.
- 2
Check Loose or corroded coil connector — A loose, corroded, or damaged connector at the coil or PCM side breaks the electrical circuit, causing signal loss.
- 3
Check Short or open in driver circuit wiring — Damaged, pinched, or shorted wiring between the PCM and ignition coil prevents proper voltage/ground connection.
- 4
Check Faulty Powertrain Control Module (PCM) — The PCM's coil driver circuit has failed, preventing it from commanding the coil properly.
How to Fix It
- 1
Replace ignition coil A
Remove the faulty coil pack from cylinder 1 and install a new OEM or quality aftermarket replacement, ensuring proper connector seating.
- 2
Inspect and repair coil connector
Check the connector at the coil for corrosion, looseness, or damage. Clean contacts with electrical contact cleaner, reseat firmly, or replace the connector if broken.
- 3
Test and repair wiring harness
Use a multimeter to check for continuity and proper voltage in the coil driver circuit wiring. Repair any shorted, open, or corroded wires between the PCM and coil.
- 4
Replace PCM if necessary
If all other components test good, the PCM's internal coil driver circuit may have failed. This requires PCM replacement and reprogramming by a qualified technician.
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