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P2304 — Ignition Coil B Primary Control Circuit High

Manufacturer-specificPowertrain (engine & transmission)

P2304 indicates that the primary control circuit of ignition coil B is detecting excessive voltage, suggesting a short to power or a faulty coil.

Symptoms

What causes it — most likely first

1. Faulty Ignition Coil B

The coil's internal primary circuit can fail, causing an abnormally high voltage reading that sets P2304.

2. Short to +12V in the coil's primary wiring

A wiring fault that connects the coil control circuit to a constant voltage source will trigger the high voltage condition.

3. Poor ground or loose connection at coil B

Insufficient grounding or a loose terminal can produce erratic voltage signals that the PCM interprets as high.

4. PCM output driver failure

A malfunction inside the PCM's coil driver circuit can cause a high voltage output, but this is uncommon.

How it's diagnosed

  1. Inspect the ignition coil B and its wiring for damage, corrosion, or loose terminals.
  2. Measure the primary circuit resistance of coil B against manufacturer specifications.
  3. Check continuity and resistance of the coil's control wiring to ground and to the PCM.
  4. Verify proper ground connections at the coil and at the PCM harness.
  5. Clear the code and monitor for recurrence after repairs.
  6. If all hardware checks are clean, test the PCM coil driver output with a scan tool.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)
Related codesP2300 — Ignition Coil Primary Control Circuit P2301 — Ignition Coil Primary Control Circuit P2302 — Ignition Coil Secondary CircuitP2303 — Ignition Coil B Primary Control CircuiP2305 — Ignition Coil B Secondary CircuitP2306 — Ignition Coil C Primary Control Circui

Frequently asked

Can replacing the PCM fix P2304?

It is rarely necessary; most cases are resolved by repairing or replacing the coil or its wiring.

Do I need to replace the entire coil pack?

Only the affected coil (B) needs replacement if it is found defective; other coils can remain in service.

Is a bad ground a common cause of this code?

Yes, an inadequate ground can cause the PCM to see an unusually high voltage, so inspect and clean all related grounds.

Will a vacuum leak trigger P2304?

No, vacuum leaks affect other sensor codes and are not directly related to the ignition coil primary circuit.