P0357 - Ignition Coil G Primary/Secondary Circuit Malfunction
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0357 is stored when the Engine Control Module (ECM) detects an issue with the primary or secondary circuit of ignition coil G (typically cylinder 7). The ECM monitors the ignition primary circuit for a specific voltage 'kick' (inductive flyback) when the circuit is opened. If the feedback signal is missing or falls outside calibrated limits, P0357 is triggered. Modern systems use this feedback to verify plug firing; failure to detect it leads to cylinder deactivation to prevent catalyst damage.
Possible Causes
Defective ignition coil (internal short or open winding)
Wiring issues (chafed insulation, corrosion, or loose pins in the connector)
Faulty spark plug (excessive resistance causing coil stress)
Failed Engine Control Module (ECM/PCM) ignition driver stage
Symptoms
Recommended Solution
- Visual Inspection: Check wiring harness and connector for coil 7 for melted wires, corrosion, or oil contamination in the spark plug well.
- Component Swap: Swap coil 7 with cylinder 1. Clear codes and drive. If the code moves to P0351, the coil is faulty.
- Electrical Testing: Verify power supply (B+ ~12.6V with ignition on) and ground. Use an oscilloscope to verify the trigger signal (Square wave) from the ECM.
- Resistance Check: Measure primary winding resistance (typically <1.0 Ohm) and secondary winding (typically 8k-15k Ohms) against OEM specs.
- Replacement: Replace ignition coil and spark plug if necessary. If wiring and coil are good, inspect ECM driver circuits.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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