P0351: Ignition Coil A Primary/Secondary Circuit
Key takeaways
- P0351 is an electrical code: the engine computer saw a bad signal in the circuit that fires ignition coil A, usually the coil for cylinder 1.
- Drive only short, gentle trips; if the check engine light starts flashing or the engine shakes hard, stop.
- Check the coil connector, wiring and grounds first ($100–$250) before buying a coil ($120–$300).
- 15 complaints filed with NHTSA mention P0351, and 7 of them are Ford Escapes, mostly 2005 models.
- Ford bulletins for P0351 point to a software update, bad engine grounds and a flywheel sensor problem, not only coils.
What P0351 means
The engine computer found an electrical problem in the circuit that fires ignition coil A. Scanners call it Ignition Coil A Primary/Secondary Circuit. The computer switches each coil on and off to make the spark, and on many engines the coil sends a confirmation signal back. When the current, voltage or feedback on coil A’s circuit isn’t what the computer expects, it sets P0351.
On most engines with one coil per spark plug, coil A is the coil for cylinder 1. On older engines where one coil fires two plugs, coil A serves a pair of cylinders. Your service information shows which.
This is a circuit code, not a misfire count. The coil itself, its connector, its wiring, its power and ground, or the computer that drives it can all set it.
Is it safe to drive?
Short trips only, and stop if the light starts flashing. When coil A drops out, its cylinder usually misfires, and you feel a shake at idle or a stumble under load. With a steady light and mild roughness, drive gently to a shop and avoid towing or hard acceleration. A flashing check engine light means the misfire is heavy enough to overheat the catalytic converter; pull over and have the car towed. The same goes for a stall or a no-start.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Loose, corroded or wet coil connector, or chafed wiring | Look at coil A’s plug for green corrosion, water or a broken lock tab; wiggle the harness with the engine running | $100–$250 |
| Failed ignition coil A | Swap coil A with a neighbor; the code changes to that coil’s number (P0352, P0353) | $120–$300 for one coil |
| Poor engine ground or coil power feed | Voltage-drop test on grounds and the coil supply; often several P035X codes at once | $100–$250 |
| Software fault | Shop finds a matching bulletin for your engine | $100–$200; often $0 under a bulletin |
| Engine computer coil driver failed | Wiring and coil test good, but the computer’s output for coil A is dead | $800–$1,800 plus programming |
What to check first
- Read all the codes. P0351 alone points to coil A’s own circuit. P0351 through P0354 together point to a shared power feed, fuse or ground.
- Inspect coil A’s connector. Unplug it, look for water, corrosion or pushed-back pins, and make sure it locks.
- Swap the coil with a neighbor, clear the code and drive. If the code follows the coil, replace the coil.
- Check power and ground at the coil with a meter or test light, including the engine-to-body ground straps.
- Suspect the computer last, only after the wiring checks out end to end.
The bulletins lean toward Ford. Ford has an engine-computer reprogram for the 2021 Mustang 5.0, a fix for poor ground connections near the coils on the 2017 Escape 1.5L EcoBoost, and a damaged flywheel sensor window on the 2015–2016 Fiesta 1.6L. GM’s bulletin for the 2014 Silverado and Sierra 1500 covers water in the coil connectors, with coil replacement.
The NHTSA complaints are thin but clustered: 7 of 15 are Ford Escapes, 6 of those from the 2005 model year. Those are owner reports, not a confirmed cause.
What it costs
The cheap outcome is a connector, ground or wiring repair, $100–$250. The common outcome is one ignition coil, $120–$300. The expensive outcome is an engine computer, $800–$1,800 plus programming, which is rare and should only follow a full circuit test. An hour of diagnosis, usually $100–$180, is cheaper than buying a coil for a corroded plug. If you want to talk through your codes first, ask our AI mechanic.
Related codes
P0351 often comes with P0301, the cylinder 1 misfire it causes, or with P0300. If P0352, P0353 and P0354 are also set, look at the shared power and ground first. For what a steady light means in general, see check engine light on and can I drive with the check engine light on.
What owners report to NHTSA
15 complaints filed with NHTSA mention P0351, 7 of them since 2015, across 9 different models. The component owners most often filed it under: electrical system.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| FORD ESCAPE | 7 | 2005, 2006 |
Manufacturer service bulletins that name P0351
17 technical service bulletins and manufacturer communications filed with NHTSA mention P0351, from 6 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- FORD MUSTANG (2021), bulletin 10198584: Some 2021 Mustang vehicles equipped with a 5.0L engine and built on or before 11-Feb-2021 may exhibit an intermittent rough running drivability concern with an illuminated malfunction indicator lamp (MIL) and diagnostic …
- CHEVROLET SILVERADO 1500 (2014), bulletin 10253407: SES Lamp P0300 P0351 - P0358.
- GMC SIERRA 1500 (2014), bulletin 10253407: SES Lamp P0300 P0351 - P0358.
- FORD ESCAPE (2017), bulletin 10137104: Some 2017 Escape vehicles equipped with a 1.5L EcoBoost engine may exhibit a misfire, lack of power, no start and/or illuminated MIL with diagnostic trouble codes (DTCs) P0351, P0352, P0353 and/or P0354 stored in the pow…
- FORD FIESTA (2015, 2016), bulletin 10092410: SOME 2015-2016 FIESTA WITH 1.6L TIVCT ENGINE MAY HAVE A CHECK ENGINE LIGHT WITH DTC'S P0351 AND/OR P0352 WITH POSSIBLE RUNS ROUGH, HARD OR NO START. FOLLOW PPT JE FOR NORMAL DIAGNOSTICS. IF LIGHT FLASH IS INCONSISTENT OR…
- FORD TRANSIT CONNECT (2014, 2015, 2016), bulletin 10094582: SOME 2014-2016 TRANSIT CONNECT VEHICLES EQUIPPED WITH THE 2.5L ENGINE MAY EXHIBIT A CONSTANT OR INTERMITTENT ILLUMINATED MIL WITH VARIOUS DRIVABILITY ISSUES AND ONE OR MORE OF THE FOLLOWING DTCS: P0010, P0103, P0104, P01…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Is P0351 the same as a cylinder 1 misfire?
Not quite. P0351 means the computer found an electrical fault in coil A's circuit. That usually causes a misfire on the cylinder the coil fires, so P0301 often shows up with it, but P0351 tells you to look at the coil circuit first.
Can I drive with P0351?
Short, gentle trips to a shop are usually fine if the light is steady and the engine runs reasonably smoothly. A flashing check engine light or heavy shaking means a strong misfire, so stop and have it towed.
Will a new coil fix P0351?
Only if the coil is the problem. Swap coil A with a neighbor first. If the code changes to that neighbor's code, such as P0352, the coil is bad. If P0351 stays, the fault is in the wiring, connector, ground or computer.
Why do I have P0351, P0352, P0353 and P0354 all at once?
Several coils rarely fail together. Look for something they share: the coil power feed or fuse, an engine ground, or a harness connector. Some cars also have a software update for this.