Code
P0357
GWM
P — Powertrain
- Malfunction in primary / secondary circuit of ignition coil G
AI status
Completed
Completed
100%
Causes
- Failed ignition coil (open/shorted primary or secondary winding)
- Damaged wiring harness or connector to coil (open, short to ground, short to battery)
- Corroded or loose coil connector or pin
- Faulty ECM/ignition driver transistor
- Poor battery/charging system voltage or ground
- Internal short in coil pack or ignition module
Symptoms
- Malfunction indicator lamp (MIL) / Check Engine Light illuminated
- Rough idle or engine misfire
- Reduced engine power and acceleration
- Poor fuel economy
- Hesitation or stumble under load
- Difficulty starting or intermittent no-start
What to check
- Read live data and freeze-frame; confirm P0357 and note any associated misfire codes (P030x).
- Verify battery and charging voltages (battery should be ~12.4–14.5 V with engine running).
- Visually inspect ignition coil G, connector and wiring for damage, corrosion, loose pins, or signs of heat.
- Wiggle test harness while engine is running to check for intermittent connections.
- Check for presence of battery power and good ground at the coil connector with key ON/engine cranking.
- Measure coil primary and secondary resistance with manufacturer spec or typical ranges.
Signal parameters
- Primary coil resistance (typical): ~0.5–2.0 ohms (consult vehicle spec)
- Secondary coil resistance (typical): ~5 kΩ–20 kΩ (consult vehicle spec)
- Supply voltage at coil connector with key ON: battery voltage (~11–14.5 V)
- Primary switching pulse: pulse width typically ~1–5 ms during cranking/running (varies with rpm/load)
- Primary current: peaks typically in single-digit to low double-digit amps depending on coil design
- Secondary voltage: can reach several kV during discharge (expected only on a good spark)
Diagnostic algorithm
- Confirm: Read DTCs and freeze-frame data. Note any concurrent misfire (P030x) or other ignition/charging codes.
- Visual inspection: Check coil G, connector, wiring harness routing for abrasion, heat damage, corrosion, loose pins.
- Power/ground check: With key ON, verify battery voltage present at coil power pin and a good chassis/ECM ground at ground pin.
- Resistance check: Remove coil and measure primary and secondary resistance; compare to specification or typical ranges. Replace if out of range.
- Swap test: Swap coil G with another bank/coil; if code follows the coil, replace the coil. If code stays on same cylinder/position, suspect wiring or ECM.
- Back-probe and measure while cranking: Use a DVOM or oscilloscope to verify primary switching pulses from the ECM and coil current draw. Look for proper pulse timing and amplitude.
- Wiring continuity: Check continuity and for shorts between coil connector and ECM. Repair any open/short/high-resistance circuits.
- ECM check: If coil and wiring test good, consult wiring diagrams and consider ECM/ignition driver failure. Confirm with dealer-level diagnostics or substitute known-good ECM if practical.
- Repair/replace parts as indicated (coil, wiring, connector, ECM). Clear codes and road-test to confirm repair.
- If intermittent, repeat tests under conditions when fault occurs and consider vibration/temperature effects.
Likely causes
- Defective coil G
- Open or shorted primary circuit conductor between ECM and coil G
- Poor power or ground at coil connector (loose, corroded, high resistance)
- Connector pin corrosion or bent/misaligned pins
- ECM driver transistor failure (if wiring and coil test good)
Fault status
Status
Ignition Coil G - Primary/Secondary Circuit Malfunction detected (P0357). Check coil, connector, wiring and ECM driver for faults; may cause misfire/no-spark on associated cylinder.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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