P2315 indicates the powertrain control module (PCM) has detected a voltage level below the expected threshold in the primary control circuit for ignition coil F (typically cylinder 6). The primary circuit is the low-voltage side that triggers the coil's internal switching device. A low signal usually points to a short to ground, an open circuit, or a failed driver inside the coil or PCM.
The coil's internal primary winding or integrated driver module can short to ground or open, pulling the control circuit low.
A short to ground, chafed insulation, corroded terminal, or loose connector at the coil or PCM can cause a low-voltage reading.
The PCM's internal driver transistor for coil F may fail low, though this is less common than coil or wiring faults.
A shared power feed or ground for the coil pack that is compromised can affect the primary control signal.
PCM failure is a rare cause of P2315. The majority of cases are caused by the ignition coil itself or wiring faults. Replacing the PCM without confirming the driver circuit has failed will not resolve the code.
Driving with an active misfire can damage the catalytic converter due to unburned fuel. The vehicle should be repaired promptly.
Most modern engines use individual coil drivers per cylinder. A fault on coil F typically affects only that cylinder's circuit.
A worn or fouled plug can increase secondary voltage demand, but it does not directly cause a primary control circuit low code. The code points to the primary circuit, not the secondary output.