Ignition Coil "B" Primary Control Circuit High
The P2304 code means the vehicle's onboard diagnostic system has detected: Ignition Coil "B" Primary Control Circuit High. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $80 - $300 (coil and plug typically; wiring repair if the harness is at fault)
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Common Symptoms
- Check Engine Light on (often with a misfire code for the same cylinder)
- Misfire, stumble, or rough running - worst under load
- Possible reduced power and fuel economy
Probable Causes (Ranked by Likelihood)
- Failed ignition coil B High
- Open/short in the coil's primary control wiring or connector High
- Connector corrosion or a damaged harness at the coil Moderate
- PCM coil driver fault Low
Frequently Asked Questions
What does P2304 mean?
P2304 means the PCM detected a fault in the primary control circuit of ignition coil B. Coil letters map to specific cylinders per engine - check your service manual for which cylinder this is on your vehicle.
Can I keep driving with P2304?
Briefly, yes - but a misfiring cylinder dumps unburned fuel into the exhaust and can overheat the catalytic converter, turning a cheap coil into an expensive converter. Fix it soon and avoid heavy load.
Should I replace all the coils for P2304?
Not necessarily. Diagnose the one coil first (the swap test takes minutes). On a high-mileage engine where one coil has failed, replacing plugs at the same time is worthwhile; replacing all coils is optional insurance, not a requirement.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Identify which cylinder coil B serves for your engine (the letter-to-cylinder map is in the service manual).
-
Swap the suspect coil with a neighboring cylinder's coil; if the code follows the coil, replace it.
-
Inspect the coil boot and spark plug - worn plugs and torn boots kill coils.
-
Check the coil connector and wiring for damage; verify power and control signals at the connector.
-
Clear codes and road-test.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- 2010-2018 Ford Fusion 2.5L
- 2012-2020 Toyota Camry 2.5L
- 2013-2021 Honda Accord 2.4L
- 2014-2022 Hyundai Sonata 2.4L
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