P0356

Ignition Coil F Primary/Secondary Circuit Malfunction

P0356 is a generic OBD-II powertrain diagnostic trouble code: Ignition Coil F Primary/Secondary Circuit Malfunction. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0356
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
Need P0356 disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P0356 means

P0356 is stored when the PCM detects an electrical fault in the primary or secondary ignition circuit for coil "F", which fires cylinder 6. The coil operates as a transformer: during dwell the PCM grounds the primary driver circuit, building a magnetic field; at the correct crank angle the driver opens, the field collapses, and 20–40 kV is induced in the secondary to fire the plug. The PCM monitors the primary feedback line continuously — if the expected current ramp is absent (open circuit) or immediate overcurrent occurs (short), the code sets. Cylinder 6 is present on inline-6, V6, V8, V10, and V12 engines. Relevant platforms include GM LS V8 (6-cylinder firing order means cyl 6 is a rear bank cylinder), Ford 5.0L Coyote, Mercedes-Benz M272 V6, Audi/VW 3.0 TFSI V6, BMW N52/N55/S55 inline-6, and larger V10/V12 platforms. On V6 engines this code is particularly common when a rear bank coil is exposed to heat-soak at engine-off. If a concurrent P0306 misfire is active, the PCM may enable a flashing MIL to protect the catalyst.

Common causes

Most-frequently reported root causes when P0356 is logged.

  • 1
    Failed ignition coil "F" (open or shorted primary winding — most common cause)
  • 2
    Open, chafed, or broken wire in the coil "F" PCM driver circuit
  • 3
    Short to ground or battery voltage on the driver line to coil "F"
  • 4
    Corroded or damaged connector at coil "F" base
  • 5
    Worn or fouled spark plug on cylinder 6 overloading the secondary circuit
  • 6
    Cracked coil body or coil boot allowing high-voltage arcing to engine ground
  • 7
    PCM low-side driver transistor failure for coil "F" (uncommon — diagnose after eliminating coil and wiring)

Symptoms drivers notice

Check engine light illuminated (flashing if P0306 misfire is active simultaneously)
Engine misfire on cylinder 6 — rough idle, stumble, or surging under load
Companion code P0306 (Cylinder 6 Misfire Detected) commonly present
Reduced engine power and throttle response
Increased fuel consumption from incomplete combustion
Potential catalytic converter damage from raw fuel in exhaust
Rough cold start if cylinder 6 is critical to cold-idle balance

How to diagnose P0356

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all codes — note whether P0306 and any other cylinder codes are present
  2. 2
    Swap coil "F" with a known-good coil on another cylinder; clear codes and road-test — if the fault migrates to the new cylinder, the coil is confirmed defective
  3. 3
    Visually inspect the coil "F" connector for corrosion, moisture intrusion, or damaged terminals
  4. 4
    Measure coil primary resistance (0.4–2 Ω) and secondary resistance (6,000–15,000 Ω); values outside spec indicate a failed coil
  5. 5
    Verify 12 V supply at the coil B+ terminal with ignition ON
  6. 6
    Check the PCM driver signal: with engine cranking, probe the control wire with an oscilloscope or LED test light — absence of a switching signal (12 V → 0 V) at ignition frequency points to a PCM driver fault
  7. 7
    Inspect and test the spark plug on cylinder 6 — replace if the electrode is worn, oil-fouled, or cracked
  8. 8
    Trace the wiring harness for coil "F" near heat sources (exhaust manifold, turbocharger) for insulation damage

Related powertrain codes

Frequently asked questions

Why does P0356 appear more often on V6 rear-bank cylinders?

Rear-bank cylinder 6 coils on V6 engines (e.g. Audi/VW transverse V6, Chrysler Pentastar V6) sit in a heat pocket between the engine and firewall. Heat-soak after shutdown accelerates silicone boot degradation and connector corrosion, making coil failure more likely on that bank compared to the front bank.

Can a bad spark plug cause P0356?

Yes. A severely worn or fouled plug raises the required firing voltage beyond what the coil can reliably produce. The secondary winding must work harder, which increases primary current draw in irregular ways that can trigger the driver fault monitor. Always inspect and replace the cylinder 6 plug as part of P0356 diagnosis.

How urgent is P0356 repair?

Repair as soon as practical. A flashing check engine light means the misfire is severe enough to damage the catalytic converter within minutes of continued driving. Even with a steady MIL, prolonged operation on cylinder 6 misfire can oil-foul the plug, wet-foul neighboring plugs, and cause raw-fuel contamination of engine oil.

Disabling P0356 in software

RaceTune can permanently disable P0356 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECU families we can disable P0356 on

We hold the DaVinci A2L disable definitions for these families, so the exact P0356 path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch MG1CP002 verified

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

Got P0356 in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file