Powertrain, generic (extended)

P2304 Ignition Coil B Primary Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Coil B control wire shorted to a voltage-carrying line
Internal fault in coil B or its built-in driver
Engine module fault (Polaris Slingshot 2026: ECM replaced)
Interrupted control line on systems that report it here (Saab Trionic 8)

Symptoms

  • Check engine light on
  • Cylinder 2 misfiring
  • Shaking at idle, weak acceleration

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–400
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ignition coilcoil driverignition wiring

Related codes

P2303P2305P0352P2301P0302

References: static.nhtsa.gov, saabwisonline.com, static.nhtsa.gov, static.nhtsa.gov.