P0358

Ignition Coil H Primary/Secondary Circuit Malfunction

P0358 is a generic OBD-II powertrain diagnostic trouble code: Ignition Coil H 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
P0358
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P0358 means

P0358 is set when the PCM detects an electrical fault in the ignition coil "H" primary or secondary circuit, which controls cylinder 8. The PCM grounds the primary driver circuit for a precise dwell period to charge the coil magnetically; at the correct crank angle it opens the driver, the magnetic field collapses, and the secondary winding induces 20–40 kV to fire the spark plug. The PCM monitors the primary driver feedback for each ignition event — an open circuit (no current rise during dwell) or a short (immediate overcurrent) causes P0358 to set. Cylinder 8 is exclusive to V8, V10, and V12 platforms. Common applications include GM LS V8 engines (cylinder 8 is right-rear on standard LS firing order), Ford 5.0L Coyote V8, Dodge HEMI 5.7L/6.4L V8, Mercedes-Benz M278/M176 V8, BMW N63/S63 V8, Audi 4.2 FSI V8, Audi/Lamborghini R8 5.2L V10, BMW S85 5.0L V10, Mercedes M275 V12, and BMW N73 V12. A concurrent P0308 misfire code commonly accompanies P0358; if the misfire rate is high enough to endanger the catalyst, the PCM activates a flashing MIL (catalyst-protect mode) and may disable fuel to cylinder 8 on some calibrations.

Common causes

Most-frequently reported root causes when P0358 is logged.

  • 1
    Failed ignition coil "H" — open or shorted primary winding (most common cause, approximately 75% of cases)
  • 2
    Open or shorted PCM driver wire for coil "H"
  • 3
    Corroded, damaged, or moisture-contaminated connector at coil "H"
  • 4
    Worn, cracked, or carbon-tracked spark plug on cylinder 8 stressing the secondary circuit
  • 5
    Damaged coil boot or cracked coil tower allowing high-voltage arc-over to ground
  • 6
    Oil or coolant in the coil bore or plug well (relevant on BMW N63, VAG engines with coil-in-well design)
  • 7
    PCM low-side driver failure for coil "H" (uncommon; rule out all external faults first)

Symptoms drivers notice

Check engine light illuminated (flashing MIL if active misfire P0308 accompanies the code)
Engine misfire on cylinder 8 — rough idle, vibration, power loss
Companion code P0308 (Cylinder 8 Misfire Detected) frequently stored simultaneously
Reduced power and acceleration across all operating conditions
Increased fuel consumption and elevated HC emissions
Catalytic converter heat damage risk from sustained raw fuel in the exhaust stream
Possible engine oil dilution with unburned fuel during extended misfire

How to diagnose P0358

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all codes — confirm P0308 is present and note any other cylinder-specific, bank, or cam/crank codes
  2. 2
    Coil swap test: move coil "H" to a known-good cylinder (e.g. cylinder 1), clear codes, and road-test — if the fault and misfire migrate to cylinder 1, the coil is defective
  3. 3
    Inspect coil "H" connector for corrosion, spread terminals, cracked housing, or moisture
  4. 4
    Measure primary resistance (0.4–2 Ω) and secondary resistance (6,000–15,000 Ω) with a multimeter; replace coil if outside spec
  5. 5
    Verify battery voltage (~12 V) at the coil B+ supply terminal with ignition ON
  6. 6
    Probe the PCM control wire with an oscilloscope or LED test light during cranking to confirm the PCM is generating a proper switching ground signal; no switching indicates a PCM driver fault
  7. 7
    Remove and inspect the cylinder 8 spark plug — electrode wear, fouling, or cracks justify replacement
  8. 8
    On engines with coil-in-well valve covers (BMW N63, VAG 4.2/4.4), inspect for oil in the plug well and address the valve cover gasket if found

Related powertrain codes

Frequently asked questions

What vehicles commonly trigger P0358?

Any V8, V10, or V12 vehicle with coil-on-plug ignition: GM full-size trucks and performance cars with LS V8 (5.3L/6.0L/6.2L), Ford Mustang GT/F-150 with 5.0L Coyote, Dodge Charger/Challenger with HEMI, BMW with N63/S63 V8 or S85 V10, Mercedes-Benz with M278/M157 V8 or M275 V12, and Audi/Lamborghini with 4.2L V8 or 5.2L V10. It cannot appear on 4-, 5-, or 6-cylinder engines.

The misfire is on cylinder 8 but the coil tested OK — what else could cause P0358?

Several possibilities: (1) the spark plug on cylinder 8 is worn or carbon-fouled enough to require more voltage than the coil can sustain, creating secondary stress visible on the primary trace; (2) the coil connector has intermittent contact from a spread terminal; (3) the wiring harness has a chafe point that shorts under engine movement; (4) on engines with coil-in-well designs, oil in the plug bore is shorting the secondary at the boot. Methodically test plug resistance, wiggle the connector, and inspect the bore before condemning the PCM.

How soon will catalyst damage occur after P0358 sets?

This depends on misfire severity and driving conditions. At idle with a steady MIL, raw-fuel damage is slower. At higher load and RPM with a flashing MIL, monolith overheating can begin within minutes of sustained driving. The general rule: stop driving if the MIL is flashing. A steady MIL allows limited low-load driving but the code should be diagnosed and repaired within a day or two.

Disabling P0358 in software

RaceTune can permanently disable P0358 — 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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