P2306

P2306 means the PCM detected a low-voltage condition on the primary control circuit of ignition coil C — the IGT command line is reading lower than the expected 0-5V (or 0-12V) reference, or the primary current monitored by the PCM is below the 5-15A peak it expects during the 2-6 ms dwell window. Cheapest-first ladder: (1) Inspect the coil C connector and pigtail for green corrosion, backed-out pins, and chafed-through insulation against brackets or the intake manifold — connector/harness faults are the #1 cause of low-side primary codes. (2) Ohm the primary winding pin-to-pin — 0.4-1.5 ohms is normal for most COPs; 0.0 ohms is shorted, OL is open, both condemn the coil. (3) Scope the IGT trigger pulse with a low-voltage scope — clean 0-5V (or 0-12V) square wave with 2-6 ms dwell; missing pulse traces back to the PCM driver or the harness between PCM and coil. (4) Verify 12V feed at the coil with key-on — battery voltage expected; low or absent feed traces back to the ignition relay or fusible link. Expensive-misdiagnosis caveat: swap coil C with an adjacent coil and clear the code — if P2306 follows the coil to the new cylinder, it's the coil; if it stays on the original cylinder, it's the harness, connector, or PCM driver. A $40 coil swap-test saves the $80 misdiagnosis fee.

Vehicle-specific patterns: 2005-2014 GM LSx V8 (LS1/LS2/LS3 in Silverado/Camaro/Corvette) sees coil C primary codes most often when the OEM coil pigtail chafes against the valve-cover bolt or the heat-shield bracket — repair the pigtail before replacing the coil. 2004-2010 Ford 4.6L/5.4L 3V Triton sees P2306 from the same melted/water-intruded COP connectors that plague all per-cylinder primary codes on this platform. 2011+ Ford 5.0 Coyote (Mustang GT, F-150) sees primary low-side codes from harness chafe over the intake manifold trim and from connector heat damage near the cylinder head. 2007-2018 Toyota 2GR-FE 3.5L (Camry, Highlander, Sienna, RAV4) and 2AZ-FE 2.4L typically run 100-150K miles before primary-circuit codes appear; failures are usually single-coil. Mercedes M271 (1.8L supercharged 4-cyl) and M273 (5.5L V8) coil primaries cluster at 80-120K miles. Mazda RX-8 Renesis rotary firing trailing/leading coils sees coil C primary codes earlier than piston engines because of rotor firing frequency. Common pattern: coil C usually maps to cylinder 3, 5, or whatever the OEM firing-order map assigns — never assume cylinder number from coil letter; verify against the OEM wiring diagram before swap-testing. Estimated repair: $40 (single coil DIY) to $320 (full set on a V8).