P2306 means the PCM has detected an abnormally low voltage condition on the primary control circuit for ignition coil "C" (usually cylinder 3). The primary circuit is the low-voltage path the PCM switches to energize and fire the coil. A "low" reading generally points to excessive resistance, a short to ground, or a component failure in that control path.
Internal shorting or primary-winding failure in the coil can pull the control circuit voltage low, making this the most common cause.
Chafed, damaged, or corroded wiring and poor pin fit can create a short to ground or high resistance on the control line.
A loose, corroded, or open ground path for the coil can increase voltage drop and cause the PCM to see a low primary circuit voltage.
The PCM's internal transistor that switches the coil can fail, but this is uncommon and should be considered only after the coil and wiring are ruled out.
Usually not. PCM failure is an uncommon cause of P2306. Most cases are resolved by replacing the ignition coil or repairing wiring and connector damage. Replace the PCM only after the coil, wiring, and grounds have been thoroughly tested.
Short trips are usually possible, but prolonged driving with a misfiring cylinder can overheat and damage the catalytic converter. The engine may also run rough and have reduced power.
No. P2306 identifies a fault in the ignition coil's primary control circuit, while P030x codes indicate that the PCM has detected actual misfires. Both may appear together, but they describe different problems.
"Coil C" typically corresponds to cylinder 3 on many engines, but the exact cylinder depends on the manufacturer and engine layout; consult the service information for the specific vehicle.