P1365 Ignition Coil A Secondary Circuit Malfunction
The P1365 code indicates a fault in the secondary circuit of ignition coil A. This circuit carries high voltage from the coil to the spark plug. The ECU has detected an anomaly in the IGF feedback signal or in the control of the coil's internal power transistor, preventing proper spark generation in the corresponding cylinder. The diagnosis is performed by monitoring secondary circuit current or ignition module response.
01. Most Common Causes
- Ignition coil A internally damaged or with deteriorated insulation
- Spark plug wire broken, carbon-tracked, or with abnormal resistance
- Spark plug with incorrect resistance or worn electrodes
- Secondary circuit wiring with short, open circuit, or excessive resistance
- Coil connector with corrosion or damaged pins
- Intermittent failure in the integrated or external ignition control module (ICM)
02. Symptoms You Will Notice
- Engine misfire, especially under load or acceleration
- Check Engine Light illuminated
- Rough idle or hesitation
- Decreased fuel economy and power loss
03. Step-by-Step Diagnosis
Scan for codes and verify P1365 is present; check for related misfire codes.
Inspect ignition coil A connector for corrosion, damage, or loose pins.
Test coil A primary and secondary resistance with a multimeter and compare to specs.
Check spark plug wire and spark plug for damage, wear, or incorrect resistance.
If wiring and components appear okay, perform a coil swap test to isolate the fault.
If the problem persists, test the ignition control module (ICM) signal and power supply.
1. Frequently Asked Questions
Is it safe to drive?▼
No, driving with this code is not recommended. The misfire can cause catalytic converter damage, reduced engine performance, and potential stalling. Have the vehicle diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on the cause. A single ignition coil replacement costs $80–$200, plus labor. Spark plugs and wires add $50–$150. ICM replacement can be $200–$400.