P0355

Ignition Coil E Primary/Secondary Circuit Malfunction

P0355 is a generic OBD-II powertrain diagnostic trouble code: Ignition Coil E 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
P0355
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P0355 means

P0355 indicates the PCM has detected a fault in the primary or secondary circuit of ignition coil "E", which drives cylinder 5. The coil is a step-up transformer: the PCM commands a low-side driver to complete the primary winding ground during the dwell period, storing energy as a magnetic field; when the driver opens, the collapsing field induces 20–40 kV in the secondary winding to fire the spark plug. The PCM monitors current feedback on the primary driver line — an open circuit (broken wire, corroded connector, failed coil primary winding) produces no current rise during dwell, while a hard short to ground or supply causes excessive current. Either fault triggers P0355. A failed secondary winding (open secondary, cracked plug, arcing boot) also loads the primary differently and can set the code. Cylinder 5 is present on all inline-5, inline-6, V8, V10, and V12 engines; it does not apply to 4-cylinder platforms. Typical applications include Ford Mustang GT/F-150 with 5.0L Coyote V8, GM LS-family V8s (5.3L/6.2L), Mercedes-Benz M137/M275 V12, Audi/Lamborghini 5.2L FSI V10, BMW S85 V10, Dodge Viper V10, and any I5 platform (Audi 2.5 TFSI, Ford Duratec 2.5 I5). The PCM typically enables a flashing MIL (catalyst-protect mode) if a companion misfire code P0305 is also active, to reduce unburned fuel entering the catalytic converter.

Common causes

Most-frequently reported root causes when P0355 is logged.

  • 1
    Defective ignition coil "E" (open or shorted primary winding — most common cause, ~75% of cases)
  • 2
    Open circuit in the coil "E" primary control wire between PCM and coil connector
  • 3
    Short to ground or short to battery voltage on the coil "E" driver circuit
  • 4
    Corroded, spread, or damaged coil "E" connector pins
  • 5
    Failed spark plug on cylinder 5 causing secondary overload that stresses primary
  • 6
    Cracked or carbon-tracked coil boot / ignition wire allowing secondary arcing to ground
  • 7
    PCM internal coil driver transistor failure (rare — confirm after ruling out wiring and coil)

Symptoms drivers notice

Illuminated check engine light (flashing MIL if active misfire P0305 is also present)
Engine misfire on cylinder 5 — rough idle, hesitation, stumble under load
Companion code P0305 (Cylinder 5 Misfire Detected) typically stored alongside
Reduced power and poor acceleration, especially at higher RPM
Increased fuel consumption due to incomplete combustion on cylinder 5
Possible catalytic converter damage if raw fuel enters exhaust during extended misfire
Hard start or stall on cold start if cylinder 5 misfire is severe

How to diagnose P0355

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored and pending codes — confirm P0305 presence and any other cylinder-specific codes
  2. 2
    Perform a coil swap: move the cylinder 5 coil to a known-good cylinder (e.g. cylinder 1) and clear codes; if the misfire and coil code follow the swapped coil, the coil is defective
  3. 3
    Inspect the coil "E" connector for corrosion, pushed-back terminals, or damage — clean and reseat if found
  4. 4
    Measure primary winding resistance at the coil (typical spec: 0.4–2 Ω); measure secondary resistance (typical spec: 6,000–15,000 Ω) — out-of-spec readings confirm a failed coil
  5. 5
    With ignition ON (engine off), verify ~12 V battery supply at the coil B+ terminal
  6. 6
    With engine cranking, use an LED noid light or oscilloscope on the PCM driver wire to confirm the PCM is issuing a ground signal (switching 12 V → 0 V at ignition frequency); no switching points to a PCM driver fault
  7. 7
    Inspect and measure resistance of the spark plug on cylinder 5 — replace if worn or fouled by oil/fuel
  8. 8
    Check wiring harness routing near exhaust manifold or hot surfaces for chafed insulation causing shorts
  9. 9
    If all external components test good, suspect PCM driver circuit failure — verify with manufacturer PIDS before condemning PCM

Related powertrain codes

Frequently asked questions

Can I drive with a P0355 code?

Short distances at reduced load are possible, but driving is not recommended. A misfiring cylinder 5 sends unburned fuel into the catalytic converter, which can overheat and destroy it — an expensive secondary repair. If the MIL is flashing, stop driving and diagnose immediately.

Will swapping the coil to another cylinder really confirm the fault?

Yes — this is the fastest diagnostic step. If you swap coil "E" (cylinder 5) to cylinder 1 and the fault code and misfire move to cylinder 1 (P0351 + P0301), the coil itself is confirmed bad. If the misfire stays on cylinder 5, the problem is in the wiring, connector, spark plug, or PCM driver for that cylinder.

What engines can get P0355?

Any engine with 5 or more cylinders and individual coil-on-plug ignition: inline-5 (Audi 2.5 TFSI, Ford 2.5 I5), inline-6 (BMW N54/N55, Mercedes OM651), V8 (Ford 5.0L Coyote, GM LS, Dodge 5.7L/6.4L HEMI, Mercedes M137), V10 (Audi/Lamborghini 5.2L, BMW S85, Dodge Viper), and V12 (BMW N73, Mercedes M275).

Is P0355 a primary or secondary circuit fault?

The code covers both. A primary fault is typically an open or short in the low-voltage PCM driver circuit or primary coil winding (0.4–2 Ω range). A secondary fault is a breakdown in the high-voltage output path — cracked coil tower, failed secondary winding, arcing boot, or worn spark plug. Either can disturb the primary current waveform enough for the PCM to log P0355.

Disabling P0355 in software

RaceTune can permanently disable P0355 — 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 P0355 on

We hold the DaVinci A2L disable definitions for these families, so the exact P0355 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.

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