P0356 Ignition coil F primary or secondary circuit fault (the coil for cylinder 6 on most engines)

Ignition Coil F Primary/Secondary Circuit Malfunction

P0356 in short

P0356 means the computer found a fault in the primary or secondary circuit of ignition coil F, usually the cylinder 6 coil. A failing coil, a loose or damaged connector, or a worn spark plug is the usual cause. Drive gently if the light is steady, and stop if it flashes.

Each cylinder has an ignition coil that makes the spark. The computer watches the circuit, and P0356 sets when the circuit for coil F does not behave as expected. Coil F is usually cylinder 6, but the lettering depends on the engine.

PartsAvatar lists a faulty coil or plug, a loose or broken coil connector, wiring corrosion or open circuits, and rarely the computer. Ford bulletin 18-2047 describes an open circuit in the cylinder 5 and 6 coil connectors on 2014 to 2016 F-250 and F-350 6.2L trucks, and Toyota issued a bulletin for coil-related P0351 to P0356 on the 2006 Highlander Hybrid.

Because coil codes can come from a shared connector or harness, look at neighboring coil codes too.

Most likely causes

  1. Failed ignition coil on cylinder 6

    Common general cause
    Why it ranks here
    The code names coil F, and PartsAvatar lists a faulty coil first. Toyota TSB-0131-09 attributes P0351 to P0356 on the Highlander Hybrid to an ignition coil malfunction.
    What would change this
    Rises if the code follows the coil when swapped. Falls if it stays with cylinder 6.
    How to test the ignition coil

  2. Loose, broken or open coil connector or wiring

    Supported by vehicle data
    Why it ranks here
    Ford TSB 18-2047 names an open circuit in the cylinder 5 and 6 coil connectors on 2014 to 2016 F-250 and F-350 6.2L trucks. PartsAvatar lists loose connections, broken connector locks and corroded wiring.
    What would change this
    Rises if the connector is loose or damaged. Falls if the wiring tests fine.

  3. Worn or fouled spark plug

    Common general cause
    Why it ranks here
    PartsAvatar lists plug problems among the causes of this code.
    What would change this
    Rises if the plug is overdue or heavily worn. Falls if it looks good.
    How to test the spark plug

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored codes and freeze-frame data, and note whether the check engine light has been flashing.

    Low riskTool: OBD-II scan tool

    • IfP0355 or other coil codes are stored too

      It meansLook at shared connectors, wiring and bulletins.

      Go to step 2

    • IfOnly P0356 is stored

      It meansInspect the cylinder 6 coil connector and plug.

      Go to step 3

  2. Ask a dealer whether your VIN has a coil or connector bulletin, such as Ford 18-2047 for 2014-2016 F-250/F-350 6.2L.

    Low risk

  3. With the engine off and cool, check the cylinder 6 coil connector, wiring and spark plug, then swap the coil with a neighbor and clear the codes.

    Use cautionTool: basic hand tools, scan tool

    Warning:Never touch coils, plug wires or connectors while the engine is running or cranking; ignition voltage can shock you. Let the engine cool before touching exhaust-side parts.

Symptoms

  • Check engine light on
  • Rough idle or hesitation
  • Misfire or loss of power under load
  • Hard starting
  • Check engine light flashing Gets more serious: stop and have it checked.

Compare with: Rough idle with the check engine light on, Car shaking with the check engine light on

How to fix

  1. With the engine off and cool, check that the cylinder 6 coil connector is fully seated and not damaged.

  2. Ask a dealer whether your VIN is covered by a coil or connector bulletin before replacing coils.

Parts and cost context

  • Ignition coil:Swap the coil with another cylinder first so you replace the right one. If the plugs are old, replace them with the coil. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

  • 2006 · Highlander

    Supported by vehicle data

    Toyota bulletin TSB-0131-09 covers the 2006 Highlander Hybrid with a MIL and coil primary circuit codes P0351 to P0356, attributed to an ignition coil malfunction. Whether it is still current is not verified.

  • TSB-0131-09Status unverified

    MIL with ignition coil A-F primary circuit DTCs (P0351-P0356), Highlander Hybrid

    2006highlander · NHTSA 10030325

    Some vehicles show a MIL with one or more coil DTCs stored because of an ignition coil malfunction. The NHTSA summary does not give the repair steps.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2014–2016 · F-250 Super Duty · 6.2L V8

    Supported by vehicle data

    Ford bulletin 18-2047 says 2014 to 2016 F-250 and F-350 trucks with the 6.2L V8 can set P0355 or P0356 from an open circuit in the cylinder 5 and 6 coil connectors. Whether it is still current is not verified.

  • TSB18-2047Status unverified

    MIL with P0355 and/or P0356, 6.2L: open circuit in coil-on-plug connectors, cylinders 5 and 6

    2014–2016f-250-super-duty, f-350-super-duty · NHTSA 10136577

    Open circuit in the cylinder 5 and 6 coil connectors caused by interference with the intake air expansion resonator; follow the service procedure.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0355Ignition coil E primary or secondary circuit fault (the coil for cylinder 5 on most engines)

    Other bank Supported by vehicle data

    P0355 and P0356 are the cylinder 5 and 6 coil codes, and Ford TSB 18-2047 covers them together on 6.2L F-250 and F-350 trucks.

  • P0354Ignition coil D primary or secondary circuit fault

    Same system Supported by vehicle data

    Lexus and Toyota coil bulletins cover P0351 to P0356 together as one ignition coil circuit family.

All Ignition and engine position sensors codes

P0356 questions

Which cylinder is coil F?

On most engines it is cylinder 6, but the lettering depends on the engine. Check the service information for your vehicle.

Is it safe to drive with P0356?

A steady light with mild roughness can be driven gently to a shop. Stop if the light flashes, because the misfire can damage the catalytic converter.

Sources and review

  1. P0356 OBD Error Code: Ignition Coil F Primary/Secondary Circuit Malfunction — PartsAvatar
  2. Toyota TSB-0131-09: MIL with ignition coil A-F primary circuit DTCs (P0351-P0356) on Highlander Hybrid — Toyota / NHTSA
  3. 2001 Lincoln Continental Owner's Guide: Warning lights (Check engine) — Ford Motor Company
  4. Ford TSB 18-2047: MIL with P0355 and/or P0356 on 2014-2016 F-250/F-350 6.2L (open circuit in coil-on-plug connectors, cylinders 5 and 6) — Ford Motor Company / NHTSA
  5. Lexus LSB-0179-09: MIL with P0351-P0356 (ignition coil primary/secondary circuit) on ES 350 and RX 350 — Lexus / NHTSA
Last reviewed
Written by
Saurabh K.
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