P2304Ignition Coil B Primary Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2304 means the control line of coil B (cylinder 2) is held at too high a voltage – usually a short to a supply line, sometimes an internal coil fault. In VW's 2014 tables a primary control circuit counts as high once its signal voltage exceeds about 5.1–7.0 V, while the low code reacts to a current above 24 mA; the Touareg six-cylinder petrol table (engine code CGRA) names the coils directly by cylinder number. Saab's Trionic 8 (9-3, 2003) sets P2304 when more than 2 V remain on the line while the module grounds it, an open line included. A rarer cause is the module itself: Polaris put six 2026 Slingshots on dealer hold because their ECM triggered P2304, and shipped replacement ECMs. Ford's Bronco bulletin 24-2406 lists P2304 among the codes that a PCM reflash may need to remap to the right cylinder.
- What you may notice
- Check engine light on
- Cylinder 2 misfiring
- Shaking at idle, weak acceleration
- Likely causes
- LikelyCoil B control wire shorted to a voltage-carrying line
- PossibleInternal fault in coil B or its built-in driver
- PossibleEngine module fault (Polaris Slingshot 2026: ECM replaced)
- RareInterrupted control line on systems that report it here (Saab Trionic 8)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.