The engine control module has detected an open electrical circuit or abnormal resistance in the primary (low-voltage) or secondary (high-voltage) winding of the ignition coil. This interrupts the magnetic field collapse required to generate spark, typically resulting in a misfire on the affected cylinder.
Internal open circuits in the primary or secondary winding are the most common cause, usually resulting from thermal degradation, insulation breakdown, or manufacturing defects over time.
Broken, chafed, or melted wires between the PCM and the coil disrupt current flow, while shorts to ground or power can trigger a circuit malfunction detection.
Poor pin contact caused by moisture intrusion, oxidation, or physically damaged connectors creates excessive resistance that the PCM interprets as an open circuit.
Excessive resistance from severely worn spark plugs, damaged plug wires, or open spark plug gaps can reflect to the primary side and set the code on some diagnostic strategies.
A rare failure of the ignition driver transistor inside the powertrain control module interrupts the ground-side control of the coil primary circuit, but this should only be considered after coil and wiring integrity are confirmed.
Limited driving is possible, but prolonged operation can overheat and damage the catalytic converter due to unburned fuel entering the exhaust. The vehicle should be diagnosed promptly to prevent secondary damage.
No, you only need to replace the specific coil setting the code. However, if coils are of similar age and one has failed, others may follow soon; replacing them as a set is a maintenance strategy, not a mechanical requirement.
PCM failure causing this code is genuinely rare. Exhaustively verify the coil, spark plugs, and every inch of wiring before considering the PCM. Most P0350 codes are resolved with coil or wiring repairs, not module replacement.
The primary circuit is the low-voltage side (battery voltage) controlled by the PCM to charge the coil. The secondary circuit is the high-voltage side that delivers spark to the plug. An open in either can set this code, though primary side opens are more common.