P2304 — Ignition Coil "B" Primary Control Circuit High
powertrain (engine/transmission)
Is it safe to drive?
Drive with caution Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.
How to diagnose with an OBD scanner
- Read the code and freeze frame Connect an OBD2 scanner, confirm P2304 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
- Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
- Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
- Subsystem check With the ignition coil "B" primary control disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
- Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
- Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
- Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2304 does not return.
Approximate repair cost
Repair cost depends on which component actually failed. Typical scenarios for P2304 (parts and labor, USD, independent shop rates): Replace spark plugs: $90–$250; Replace an ignition coil: $150–$380; Repair coil wiring or connector: $80–$250. Overall, fixing P2304 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.
Common questions
How do I diagnose P2304 myself?
Start with a scan: confirm P2304, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ignition coil "B" primary control, and verify the suspect component against live data before buying parts.
What are the symptoms of P2304?
Drivers most often notice: increased fuel consumption, loss of power and jerking, hard starting, especially in damp weather, misfires under load or at idle.
How much does it cost to fix P2304?
Replace spark plugs — $90–$250; Replace an ignition coil — $150–$380; Repair coil wiring or connector — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.
Will P2304 clear itself?
Sometimes P2304 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.
What is the most common cause of P2304?
The most common causes are: failed ignition coil or coil pack, faulty ignition control circuit in the ECM, moisture or oil in the spark plug wells.
What does P2304 mean?
P2304 (Ignition Coil "B" Primary Control Circuit High) is stored when self-diagnostics detect abnormal readings or behaviour of the ignition system. It belongs to the powertrain (engine/transmission) category.
“Circuit high” means the control module sees a voltage on the ignition coil "B" primary control circuit that is above the expected range — typically close to battery voltage. Physically this points to a short to a power feed, a broken ground return, or a failed component pulling the signal line high.
To set P2304, the control module compares live readings of the ignition system against calibrated limits, usually over several drive cycles. Alongside the code it stores a freeze frame — a snapshot of rpm, load, coolant temperature and vehicle speed at the moment of failure. Reading that snapshot first saves diagnostic time.
What causes P2304?
- failed ignition coil "B" primary control pulling the signal high
- open ground return of the ignition coil "B" primary control
- signal wire shorted to battery positive
- damaged coil wiring or connector
- worn spark plugs or wrong plug gap
- moisture or oil in the spark plug wells
- failed ignition coil or coil pack
- faulty ignition control circuit in the ECM
Common symptoms of P2304
- increased fuel consumption
- loss of power and jerking
- hard starting, especially in damp weather
- misfires under load or at idle
- Check Engine Light on
How to diagnose P2304
- Connect an OBD2 scanner, confirm P2304 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
- Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
- Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
- With the ignition coil "B" primary control disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
- Swap the coil to another cylinder and see if the fault code follows it.
- Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
- Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2304 does not return.
How to fix P2304
Start with the cheapest and most common causes before replacing expensive parts:
- Replace spark plugs — $90–$250
- Replace an ignition coil — $150–$380
- Repair coil wiring or connector — $80–$250
How much does it cost to fix P2304?
Repair cost depends on which component actually failed. Typical scenarios for P2304 (parts and labor, USD, independent shop rates):
- Replace spark plugs: $90–$250
- Replace an ignition coil: $150–$380
- Repair coil wiring or connector: $80–$250
Overall, fixing P2304 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.
Can you drive with P2304?
Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.