P0351: Ignition Coil A Primary Control Circuit/Open
P0351 means the engine computer found an open circuit (a break in the wiring, or very high resistance) in the control line to ignition coil A, which usually fires cylinder 1. It is a moderately serious fault because the cylinder can misfire or be shut off, and driving on can damage the catalytic converter.
You can drive, but get it checked soon
The car may run, but the affected cylinder can misfire or be shut off, and unburned fuel can overheat and damage the catalytic converter. Limp mode (reduced power) is possible. Keep trips short and gentle until it is fixed, and stop if the check engine light flashes or the engine runs badly.
What it means
Each cylinder has its own ignition coil that makes the high voltage for the spark plug. The engine computer (engine module) switches the coil on and off through a control line called the primary control circuit. With P0351, the computer sees that this line to coil A is open or has too much resistance, so the coil is not getting its switching signal or is not responding. Coil A usually serves cylinder 1, but the manufacturer decides the assignment. Some manufacturers check continuously and respond fast: Ford expects a current feedback for every ignition command and shuts off fuel injection to that cylinder for 30 seconds at a time. Short circuits and faults on the high-voltage side set other codes (the P2300 family).
Likely causes
- Faulty ignition coil AVery likely
The coil's built-in output stage or its primary winding can fail open, which is the most common reason for this code.
- Corroded, loose or spread connector at the coilVery likely
A poor contact in the plug breaks the control line even when the coil itself is fine.
- Open or chafed control, supply or ground wirePossible
A broken or rubbed-through wire between the coil and the engine module interrupts the circuit.
- Blown fuse or faulty relay for the coil supplyLess likely
This usually affects several coils, so you would normally see several codes instead of only P0351.
- Faulty driver in the engine moduleLess likely
The switching stage inside the computer can fail, but this is rare compared with coil and wiring problems.
What you may notice
- Check engine light on
- Misfire and rough running on cylinder 1, often with P0301 as well
- Loss of power and jerking under load
- Cylinder shut off (injection off), with a risk to the catalytic converter if you keep driving
What to check, cheapest first
- 1Read all stored codes and note any misfire codes such as P0301 or P0300, and any other coil codes. · you can do it
- 2Inspect the connector at coil A for corrosion, looseness or bent or spread pins, and reseat it firmly. · you can do it
- 3Look at the visible wiring to the coil for chafing, breaks or damage. · you can do it
- 4Swap coil A with a coil from another cylinder, clear the code and see whether the fault moves with the coil. If it does, replace that coil. · you can do it
- 5Check the coil supply fuse and relay, especially if several codes are present. · mechanic
- 6Test the control, supply and ground wires for continuity, and check the engine module driver if the wiring and coil test good. · mechanic
Related codes
Frequently asked questions
Can I drive with P0351?+
Only briefly and with care. The cylinder may misfire or be shut off, which can harm the catalytic converter. Get it repaired soon.
Can a gas cap cause P0351?+
No. This code points to the ignition coil circuit: the coil, its connector, the wiring or, rarely, the engine module.
Will P0351 pass an emissions test?+
Unlikely. The code is emissions-relevant and turns on the check engine light, so the fault should be repaired and the light off before testing.
Can I fix P0351 myself?+
Often yes. The repair is rated easy, typically 0.3 to 1.5 hours, such as reseating a connector or replacing the coil.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10