P2306 Ignition coil control circuit: signal or voltage too low ("C")

By: Diagno editorial team · Updated: 2026-10-15

P2306 means: Ignition coil control circuit: signal or voltage too low ("C"). The ignition coil makes the spark for the spark plug. Drive gently and have the car checked soon. The most common repair costs about €45–90 in Estonia, depending on make and model. The most common cause: connector loose, damp or corroded.

What it means

The ignition coil makes the spark for the spark plug. The computer found a fault in the coil circuit. The signal voltage is too low. Usually a wire is broken, a connector is loose or a wire is shorted to ground.

What you may notice

• Engine light on
• Misfire on one cylinder
• The engine shakes

What could be wrong

1. 1Connector loose, damp or corroded · Wiring or connector repair €45–90
2. 2Wire broken or shorted to ground · Wiring or connector repair €45–90
3. 3Faulty ignition coil · Ignition coil replacement €90–180
4. 4Engine computer fault (rare) · Control unit check and software €150–300

Repair difficulty: Easy

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Check the coil connector. Swap the coil with the next cylinder and see whether the fault follows it. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the ignition coil

Standard SAE description: Ignition Coil "C" Primary Control Circuit Low