Code
P0356
GWM
P — Powertrain
- Fault in primary / secondary circuit of ignition coil F
AI status
Completed
Completed
100%
Causes
- Faulty ignition coil F (internal open/short)
- Open or short in primary wiring (ECU → coil)
- Open or short in secondary/high-voltage circuit (coil → spark plug)
- Poor or corroded connector pins/terminals or poor ground
- Worn or fouled spark plug or incorrect gap
- Intermittent wiring damage (chafing, water ingress)
Symptoms
- Check engine / MIL lamp on
- Rough idle or engine vibrates
- Misfire on the affected cylinder (may set P030x)
- Reduced power and poor acceleration
- Hard start or extended cranking
- Increased fuel consumption and emissions
What to check
- Read and record freeze-frame data and stored related DTCs (e.g., misfire codes)
- Visual inspection of coil F, boot and spark plug for damage, carbon tracking or moisture
- Inspect connector and wiring for corrosion, loose pins, breaks or rubbing
- Measure battery and charging system voltage under cranking and at idle
- Swap coil F with another known-good coil (if coils are interchangeable) and see if code follows the coil
- Use a digital multimeter or lab scope to check primary and secondary circuits and waveforms
Signal parameters
- Primary coil resistance: typically ~0.2–2 Ω (manufacturer-specific)
- Secondary coil resistance: typically ~5 kΩ–20 kΩ (varies by coil type)
- ECU primary drive: logic-level switching (0–12 V) on the coil primary control
- Expected primary waveform: clean square/triangular current pulse when fired (use oscilloscope)
- Secondary output: high-voltage pulse sufficient to jump spark plug gap (several kV; meter-only checks require coil-specific procedures)
Diagnostic algorithm
- Connect a scanner and confirm P0356 plus any related DTCs; record freeze-frame data.
- Perform a visual inspection: unplug connector, inspect for corrosion, bent pins, water intrusion, or carbon tracking on the boot/spark plug.
- Check battery voltage (should be ~12.4 V+ at rest, >10 V during cranking). Verify good grounds.
- Swap coil F with a neighboring coil (if same part number). Clear codes and run engine: if code moves to the other cylinder, coil is suspect.
- Measure primary coil resistance at the coil connector per manufacturer spec. Replace if open or out of range.
- Measure secondary coil resistance (if specified) or inspect plug/boot condition. Replace coil if secondary is out of spec or shows internal short.
- Using a lab scope, observe the primary coil waveform while cranking/ran: look for missing pulses, abnormal dwell/current, or shorted waveform.
- If primary wiring is open/shorted, back-probe and continuity-check between coil and ECU connector; repair harness/connector as needed.
- If wiring and coil bench-tests good but fault persists, check/replace spark plug and boot. Re-test.
- If all wiring, coil and spark plug check good, investigate ECU ignition driver circuit (consult manufacturer procedures before replacing ECM).
- After repairs, clear codes and perform test drive and re-scan to confirm DTC does not return.
Likely causes
- Failed ignition coil F
- Loose/corroded connector or pin at the coil
- Damaged primary wire or short to ground/power
- Bad or worn spark plug on the same cylinder
- Intermittent mechanical damage or moisture in coil boot
Fault status
Status
Ignition Coil F Primary/Secondary Circuit Malfunction — Fault detected in primary or secondary ignition coil circuit for coil F. Inspect coil, wiring, connectors and related components.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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