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DTC codes / Ford codes / P1365

P1365 · FordIgnition Coil Secondary Circuit Failure

P1365 on a Ford means the powertrain control module (PCM) has detected a fault in the secondary, high-voltage side of an ignition coil circuit, where the spark actually jumps the plug gap. The PCM monitors coil feedback and charging behaviour and flags the code when the secondary circuit does not perform as expected, which can cause a misfire or a dead cylinder.

SystemPowertrain
Code typeFord specific
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Check engine light or service engine soon light illuminated, often with no other obvious symptom
  • Engine misfire felt as a shake, stumble, or rough idle, especially under load or acceleration
  • Noticeable loss of power and poor fuel economy from a dead or weak cylinder
  • Shaking or vibration that worsens when climbing hills or towing
  • A flashing check engine light in severe cases, indicating a misfire that can damage the catalytic converter
  • Occasional hard starting or rough running after a cold start on affected Ford engines

Common causes, most likely first

  1. Failed ignition coil on the affected cylinder, with an open or shorted secondary winding
  2. Worn or fouled spark plug that raises the voltage needed to fire and stresses the coil
  3. Damaged or corroded coil boot and spring that lose contact with the plug terminal
  4. Chafed, cracked, or oil-soaked coil wiring harness or connector at the coil
  5. Moisture or coolant intrusion into the spark plug well, common on Ford modular and EcoBoost engines
  6. PCM driver circuit fault or poor ground at the coil mounting point
  7. Aftermarket or incorrect-heat-range spark plugs that alter secondary circuit resistance

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data, then check for related misfire codes to confirm which cylinder is affected
  2. Inspect the coil, boot, and spark plug well for moisture, oil, corrosion, or a cracked insulator before replacing anything
  3. Swap the suspect coil with a known-good coil from another cylinder and see whether the misfire follows the coil
  4. Remove and inspect the spark plug for wear, gap, and fouling, and replace plugs as a set if they are due
  5. Check coil connector pins and harness continuity, and verify the coil ground and power feed with a multimeter
  6. Perform a secondary ignition or coil output test, and if the coil is confirmed faulty, replace it with a quality part
  7. Clear the code, road test under load, and verify the misfire counter and monitor status stay clean

What Ford coil misfires really tell you

  • A P1365 is frequently set by a worn spark plug or a bad coil boot rather than the coil body itself, so replacing the coil without checking the plug and boot often leaves the misfire in place.
  • On Ford engines with coil-on-plug ignition, coolant or washer fluid leaking into the plug well causes secondary circuit faults that look electrical but are really contamination problems.
  • A single failed coil can set P1365 and a cylinder-specific misfire code together, and the misfire code identifies the cylinder while P1365 confirms the secondary circuit is the problem.
  • Swapping coils between cylinders is the fastest free test, but on some Ford engines the coil hold-down bolts and connectors differ, so confirm the swap is physically possible first.
  • A flashing check engine light with P1365 means raw fuel is reaching the catalytic converter, so continuing to drive can turn a cheap coil repair into an expensive converter replacement.

Can I keep driving with P1365?

You can usually drive a short distance to a shop if the light is steady and the engine runs smoothly, but avoid hard acceleration and towing. If the check engine light flashes or the engine shakes badly, stop driving because unburned fuel can destroy the catalytic converter.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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