P0370 — Ignition Coil L Primary/Secondary Circuit Malfunction
Drivable short-term, but fix now to avoid damage.
What P0370 means
This code means the engine computer detected a fault in the electrical circuit for ignition coil L, which provides spark to one of the cylinders. It typically points to a failing coil, damaged or shorted wiring, or a loose or corroded connector. It's a common code and is usually fixed by replacing the affected coil and repairing any wiring issues.
Common symptoms
- Check engine light is on or flashing
- Rough idle or noticeable engine vibration
- Hesitation or reduced power on acceleration
- Engine misfire or stumbling
- Reduced fuel economy
Common causes
- Failed or weak ignition coil
- Corroded or loose coil connector
- Damaged or shorted wiring in the coil circuit
- Fouled or worn spark plug
- Faulty engine control module (uncommon)
Typical repair cost
$100 – $350
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0370 code?
Usually for a short trip, but not for long. A misfiring cylinder can overheat and damage your catalytic converter, leading to a far bigger expense. If the engine shakes badly or the light flashes, stop and have the vehicle towed.
How much does it cost to fix a P0370 code?
Most repairs cost between $100 and $350. The coil itself is affordable and quick to swap out. The bill grows if wiring or connectors need attention or if a technician replaces several coils at once.
Is a P0370 code serious?
It's worth fixing promptly. A single misfire won't immediately strand you, but it can damage emissions parts and make the engine run rough if left alone. Plan to repair it soon rather than waiting.
Does this code mean my whole engine is failing?
No. This code points to one ignition coil, not the entire engine. Replacing the faulty coil L and checking its wiring usually restores normal running without major engine work.