P0357

Ignition Coil G Primary/Secondary Circuit Malfunction

P0357 is a generic OBD-II powertrain diagnostic trouble code: Ignition Coil G 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
P0357
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P0357 means

P0357 indicates a malfunction in the ignition coil "G" circuit, which serves cylinder 7. The PCM controls each coil via a dedicated low-side driver transistor: it grounds the primary circuit for a calculated dwell time to build magnetic energy, then opens the circuit to generate the high-voltage spark. Feedback current on the primary line is monitored each ignition event — no current (open) or overcurrent (short) within the driver circuit triggers P0357. Cylinder 7 exists only on V8, V10, and V12 platforms, and on inline-8 engines (very rare in modern vehicles). Common applications: GM LS 5.3L/6.0L/6.2L V8 (cylinder 7 is left-rear on standard LS firing order 1-8-7-2-6-5-4-3), Ford 5.0L Coyote V8, Dodge HEMI 5.7L/6.4L V8, Mercedes-Benz M278 V8, BMW N63 V8, Audi/VW 4.2 FSI V8, Bentley 6.75L V8, Audi R8 5.2L V10, BMW S85 V10, and V12 platforms such as BMW N73 and Mercedes M275. A simultaneous P0307 misfire code will typically cause the PCM to enter catalyst-protection mode with a flashing MIL.

Common causes

Most-frequently reported root causes when P0357 is logged.

  • 1
    Faulty ignition coil "G" — failed primary winding (open or short) is the most frequent cause
  • 2
    Open or short circuit in the PCM driver wire for coil "G"
  • 3
    Damaged or corroded connector at coil "G"
  • 4
    Worn, fouled, or cracked spark plug on cylinder 7 that overloads the secondary circuit
  • 5
    Cracked coil boot or coil body allowing high-voltage arc to engine block
  • 6
    Water or oil intrusion into the coil bore (common on engines with valve cover coil pockets)
  • 7
    PCM coil driver transistor failure for cylinder 7 (uncommon)

Symptoms drivers notice

Check engine light on (flashing if concurrent P0307 misfire is active)
Engine misfire specific to cylinder 7 — rough idle, hesitation, power loss
P0307 (Cylinder 7 Misfire Detected) commonly stored alongside P0357
Decreased engine power output and poor throttle response
Higher fuel consumption and elevated hydrocarbon emissions
Risk of catalytic converter overheating from unburned fuel if left unrepaired
Possible oil dilution with fuel if misfire persists for extended periods

How to diagnose P0357

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs — check for P0307 and any other cylinder-specific or bank-specific codes
  2. 2
    Perform coil swap test: move coil "G" to a known-good cylinder, clear codes, and test drive — if the code and misfire follow the coil, replace it
  3. 3
    Inspect the cylinder 7 coil connector for corrosion, moisture, bent pins, or cracked housing
  4. 4
    Measure coil primary resistance (0.4–2 Ω) and secondary resistance (6,000–15,000 Ω); replace coil if out of spec
  5. 5
    Verify ~12 V at the coil power supply terminal with ignition ON
  6. 6
    Use an oscilloscope or LED noid light on the PCM control wire to confirm a switching ground signal during cranking
  7. 7
    Remove and inspect the cylinder 7 spark plug — replace if electrode gap is excessive, electrode is worn, or plug shows oil/carbon fouling
  8. 8
    Check for oil or coolant in the coil bore (common on BMW N63, VAG 4.2 FSI) — address the leak source before fitting a new coil

Related powertrain codes

Frequently asked questions

Which engines can get P0357?

Only engines with at least 7 cylinders: V8 (GM LS, Ford Coyote, Dodge HEMI, BMW N63, Mercedes M157/M278, Audi 4.2 FSI), V10 (Audi/Lamborghini 5.2L, BMW S85, Dodge Viper 8.4L), and V12 (BMW N73/N74, Mercedes M275, Bentley W12 counts cylinders differently). It will never appear on 4-cylinder or V6 engines.

Is P0357 the same fault as P0307?

No, but they often appear together. P0357 is a circuit/electrical fault detected by the PCM on the coil driver line. P0307 is a combustion/misfire fault detected by the crank sensor monitoring rotational speed variations. P0357 can cause P0307 (no spark = misfire), but P0307 can also appear without P0357 (bad injector, low compression, lean mixture). Diagnosing P0357 first is the correct priority.

Can oil leaks cause P0357?

Yes, especially on engines where coils sit in wells in the valve cover (BMW N63, VAG 4.2/4.4 FSI). Oil leaking past the valve cover gasket into the coil pocket degrades the silicone boot, contaminates the plug well, and eventually shorts the coil secondary to the plug tube wall. Always check for and eliminate valve cover oil leaks before condemning the coil alone.

Disabling P0357 in software

RaceTune can permanently disable P0357 — 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.

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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