P0356⚡ Ignition (coil F, usually the cylinder 6 coil)Stop and fix promptly

P0356: Ignition Coil F Primary/Secondary Circuit (Meaning, Causes, Fixes)

Reviewed 2026-10-25 · Based on 2 cited source(s)

What P0356 means

On most modern engines each cylinder has its own coil sitting right on top of the spark plug (coil on plug). OBD-Codes.com explains that each coil has two wires: a battery feed, usually from the power distribution center, and a driver circuit from the powertrain computer (PCM). The PCM grounds and ungrounds the driver circuit to fire the coil and watches that circuit for faults. If it detects an open or a short in the driver circuit for coil number 6, P0356 may set, and depending on the vehicle the PCM may also shut off the fuel injector to that cylinder. RepairPal similarly says the PCM uses transistors called drivers to switch the coils, and sets P0356 if it cannot control the coil. It is a generic code that applies to OBD-II vehicles, though repair steps vary by make and model. The sources differ a little. RepairPal rates the code Urgent and lists decreased performance and increased fuel consumption as symptoms, while OBD-Codes.com gives no rating and lists the check engine light and misfires. OBD-Codes.com also lists loose connectors and broken connector locks, which RepairPal folds into a general wiring issue. P0351 through P0355 cover coils A through E, and P0357 and up cover coils G onward.

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon and go easy on the engine until then. RepairPal rates P0356 Urgent, meaning immediate action is needed, and lists decreased engine performance and higher fuel use. OBD-Codes.com gives no severity rating and lists the check engine light and a misfire that may be present or intermittent. It also notes that on some vehicles the computer may shut off the fuel injector to that cylinder. If the check engine light is flashing, the engine is misfiring badly, so stop hard driving and get it looked at.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Short to voltage or short to ground in the coil driver circuit (OBD-Codes.com)
  2. Open in the coil driver circuit (OBD-Codes.com)
  3. Loose connection at the coil or broken connector locks (OBD-Codes.com)
  4. Wiring issue (RepairPal)
  5. Bad ignition coil (OBD-Codes.com, RepairPal)
  6. Faulty engine computer (PCM) (OBD-Codes.com, RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. If the engine isn't misfiring right now, the problem is likely intermittent. OBD-Codes.com suggests wiggling the wiring at the number 6 coil and along the harness to the computer; if that brings on the misfire, repair the wiring. Check the coil connector for a poor connection and make sure the harness isn't misrouted or chafing.
  2. If the engine is misfiring now, OBD-Codes.com describes stopping the engine, unplugging the number 6 coil, then starting the engine and checking for a driver signal at the connector, either with a scope or with a voltmeter on the AC hertz scale. A reading of roughly 5 to 20 Hz means the computer is firing the coil, so the coil is likely bad. Unplug the connector with the engine off, and keep hands clear of the ignition system while it runs.
  3. If there's no driver signal, OBD-Codes.com says to check the driver wire for DC voltage (a short to voltage), then with the ignition off and the computer unplugged check the wire for continuity from computer to coil and for infinite resistance to ground. Repair any open or short you find.
  4. Only if the wiring is good and there's still no trigger signal does OBD-Codes.com suspect the computer's coil driver, and it warns that a wiring fault may have caused the computer to fail, so recheck the wiring after any computer replacement. If the engine isn't misfiring and the coil fires properly but the code keeps coming back, it says the computer's coil monitoring may be at fault.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The check engine light is flashing or the engine misfires badly
  • You don't have a multimeter, scope or wiring diagram for the coil driver circuit
  • The code comes back after a new coil
  • Tests point to the engine computer, which may need programming to your vehicle
  • Several coil codes (P0351 through P0358 or others) are set at once

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0356?

Only gently and for a short time. RepairPal rates it Urgent, and OBD-Codes.com says the engine may misfire and some vehicles shut off fuel to that cylinder. Get it diagnosed soon, and stop hard driving if the check engine light flashes.

Which cylinder is coil F?

OBD-Codes.com describes P0356 as a fault in the driver circuit for coil number 6 on coil-on-plug engines. Check your vehicle's service information to confirm which coil is F on your engine.

Is P0356 always a bad coil?

No. RepairPal lists coil replacement as the most common repair, but both sources also list wiring problems and the engine computer, and OBD-Codes.com adds loose connectors. Check the wiring and the driver signal before buying a coil.

How much does it cost to fix P0356?

Neither source gives a repair cost for P0356. It can be a loose connector, a coil or a wiring repair, so diagnose it before buying parts.

Sources

  1. OBD-Codes.com: P0356 Ignition Coil F Primary/Secondary Circuit Malfunction
  2. RepairPal: P0356 Ignition Coil "F" Primary/Secondary Circuit (rated Urgent)

Last reviewed 2026-10-25. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.