Ignition Coil Primary Control Circuit Low
The P2315 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the primary control circuit of a specific ignition coil. This circuit is responsible for triggering the coil to fire the spark plug. A low voltage reading suggests a problem with the coil itself, its wiring, or the PCM driver. This can lead to misfires, reduced engine performance, and increased emissions.
1. Most Common Causes
- Internal damage or altered primary resistance in ignition coil 'F'
- Excessive resistance, short to ground, or poor connection in the primary control circuit wiring
- Corrosion, bent pins, or moisture in the ignition coil connector
- Failure of the ignition control transistor inside the ECM/PCM
- Poor ground in the control circuit or ignition coil
- Low battery or charging system voltage affecting ECM/PCM control
2. Symptoms You Will Notice
- Check Engine Light on
- Engine misfire or rough idle
- Reduced power and acceleration
- Poor fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for codes and note which cylinder(s) are affected.
Step 2: Visually inspect the ignition coil and wiring for damage or corrosion.
Step 3: Test the primary circuit voltage at the coil connector with a multimeter (should be near battery voltage with key on).
Step 4: Swap the suspect coil with another cylinder and see if the code follows.
Step 5: If wiring and coil are good, test the PCM output for the affected circuit.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a misfire can damage the catalytic converter and reduce fuel economy.
How much does it cost to fix?▼
Typically $150-$300 for parts and labor, depending on the coil and labor rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.