P2320
Ignition CoilGSecondary CircuitP2320 is a generic OBD-II powertrain diagnostic trouble code: Ignition CoilGSecondary Circuit. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P2320 means
P2320 indicates a fault detected in the secondary circuit of ignition coil B, which corresponds to the coil serving the cylinder designated as B in the manufacturer's numbering convention (often cylinder 2 or the second coil in a coil-on-plug arrangement). The ECM monitors ionization current or coil charge/discharge characteristics and has detected an abnormality indicating the secondary winding or its high-voltage path is not functioning correctly.
Secondary circuit faults differ from primary circuit faults in that they involve the high-voltage side: the coil secondary winding, the spark plug wire (if fitted), the spark plug itself, and the ignition tower connections. A degraded secondary can still fire intermittently, causing a misfire that may not always set a dedicated misfire code alongside P2320. Carbon tracking inside a coil boot or a cracked coil body are common secondary failure modes.
Diagnosis should begin with a visual inspection of the coil, boot, and spark plug condition before moving to resistance measurements. Swapping the suspect coil to a different cylinder and checking whether the fault moves with it is a reliable and low-cost confirmation method on coil-on-plug systems.
Common causes
Most-frequently reported root causes when P2320 is logged.
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1
Failed ignition coil B secondary winding with excessive resistance or open circuit.
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2
Carbon tracking or cracking in the coil boot creating a secondary ground path.
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3
Worn or fouled spark plug on the cylinder served by coil B causing high secondary load.
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4
Cracked or damaged spark plug wire (where applicable) increasing secondary resistance.
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5
Moisture intrusion into the coil well causing intermittent secondary arcing.
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6
Poor contact between coil tower and spark plug terminal.
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7
ECM internal ignition driver fault affecting coil B firing signal.
Symptoms drivers notice
How to diagnose P2320
A typical diagnostic flow when this code is present.
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1
Retrieve all DTCs and note any accompanying misfire codes for cylinder identification.
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2
Remove the coil for cylinder B and inspect it, the boot, and the spark plug well for moisture or carbon tracking.
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3
Inspect the spark plug on cylinder B for wear, fouling, or cracking.
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4
Swap the coil from cylinder B to a known-good cylinder and clear codes; check whether the fault follows the coil.
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5
Measure secondary resistance of the suspect coil and compare to specification.
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6
Inspect the wiring harness and connector at the coil for damage or corrosion.
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7
If coil and spark plug are confirmed good, check the ECM coil driver output signal.
Related powertrain codes
Frequently asked questions
What cylinder is B in P2320?
SAE designates B as the second cylinder in firing order or the second bank; consult the vehicle-specific service manual to confirm the exact cylinder number.
Can a bad spark plug cause P2320?
Yes. A worn or fouled spark plug dramatically increases the voltage demand on the secondary circuit and can cause the coil secondary to fail prematurely or misfire.
How do I confirm the coil is bad and not the plug?
Replace the spark plug first since it is less expensive; if the code returns, swap the coil to another cylinder and see if the fault code moves to the new location.
Will P2320 damage the catalytic converter?
Prolonged misfiring from a secondary circuit fault can send unburned fuel into the exhaust, overheating and damaging the catalytic converter; address the fault promptly.
Disabling P2320 in software
RaceTune can permanently disable P2320 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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