P2304

Ignition Coil B Primary Control Circuit High

Q: Is it safe to drive with P2304?

Only briefly. A dead or weak coil means one cylinder isn't firing, and unburned fuel can overheat and damage the catalytic converter. Fix it soon, especially if the light is flashing.

Q: Can I just clear P2304?

It will return quickly if the coil or its wiring is faulty. Clearing it does not fix the misfire.

Ignition Generic OBD-II Medium

What it means

P2304 means the ECM has seen high voltage on the primary control circuit for ignition coil B, so that coil may not be firing its cylinder correctly. The result is usually a misfire, rough idle, and reduced power. Common causes are a failed coil, a wiring or connector fault, or a short to voltage in the control circuit.

Medium

Can I keep driving? Drivable but likely misfiring on one cylinder — avoid extended or hard driving, as a sustained misfire can damage the catalytic converter.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on (may flash during an active misfire)
Rough idle and engine shake
Hesitation or stumble on acceleration
Reduced power and rougher running under load

Common causes

Most likely first

Failed ignition coil BLikely
Open or short-to-voltage in the coil B primary control wiringCommon
Corroded or loose coil connectorCommon
Poor ground or chafed harness near the coilLess often
Faulty ECM/ignition-module driver (less common)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data and note any cylinder-specific misfire codes.
Inspect the coil B connector and wiring for damage, corrosion, or a spread pin.
Swap coil B with a neighbouring coil and see if the fault follows the coil.
Check the primary control wire for an open or short to voltage back to the ECM.
Replace the coil if it fails testing; repair wiring faults otherwise. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P2304?+

Only briefly. A dead or weak coil means one cylinder isn't firing, and unburned fuel can overheat and damage the catalytic converter. Fix it soon, especially if the light is flashing.

Can I just clear P2304?+

It will return quickly if the coil or its wiring is faulty. Clearing it does not fix the misfire.

Read & clear P2304 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX