What it means
The primary control circuit of ignition coil L reads a voltage below the expected level — usually a short to ground on the primary driver wire or a low-resistance fault in the coil primary winding. Coil L cannot build a normal charge, so the cylinder it fires misfires, especially under load. Causes: short to ground in the primary wiring, an internal coil primary fault, or a faulty ECU/igniter driver.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The coil L primary control circuit switches current through the coil's primary winding so it can build the magnetic field needed for a spark. The controller sets this code when it detects abnormally low voltage on that circuit, such as from a short to ground or a coil fault, and the coil L cylinder may misfire.
Common causes
Most likely first.
- Primary winding shorted to ground or harness chafed
- Coil L internal driver fault
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Engine misfire or rough running
- Reduced power or hesitation
How to diagnose it
- Save freeze-frame data and check misfire counts for the cylinder served by coil L, noting whether the fault appears under load.
- With the ignition off, inspect coil L's connector and harness for chafing, pin damage, corrosion, or contact with ground.
- Check that coil L has its required power and ground connections, following the vehicle wiring diagram and manufacturer's procedure.
- Test the coil L primary control wire for a short to ground and check the coil primary winding for an abnormal short using the manufacturer's specifications.
- If the wiring and coil pass, test the ECU or igniter driver output according to the manufacturer's procedure.
Common fixes
- Repair chafed coil L control wiring that is shorted to ground.
- Clean or repair corroded or damaged coil L connector terminals.
- Replace coil L if its primary winding fails the specified test.
- Repair or replace the ECU or igniter driver only after confirming the circuit and coil are sound.
Can I keep driving?
Keep driving only gently and briefly if the engine runs smoothly; avoid heavy load because the coil L cylinder may misfire and emissions can rise. If it runs rough or the check-engine light flashes, stop driving to limit catalytic-converter damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.