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2010 Hyundai Genesis Coupe - Code P0456: Emission Control System Leak - Slow Start & Starting Issues

Model: 2010 HYUNDAI GENESIS COUPE Fault Code: P0456 Posted: 2014-12-17 10:26

My 2010 Hyundai Genesis Coupe has recently developed a check engine light, and my diagnostic tool detected code P0456 — indicating an emission control system leak (small). Since the warning light appeared, I've noticed a significant issue: when I try to start the car, it doesn't crank immediately. Instead, turning the key results in all dashboard lights illuminating, similar to having a dead battery. The vehicle appears unresponsive at first, and only after pressing the gas pedal all the way to the floor does it eventually start — but with a very weak, delayed response. I'm wondering if the P0456 code directly interferes with the starting process. I plan to check my fuel tank cap when I leave for lunch to ensure it's securely fastened and sealed. Could this leak be causing both the engine light and the slow cranking? Or is there another underlying issue, such as a failing battery or starter? I’ve previously left an interior light on overnight about two months ago, which led to a dead battery — I jumped it then and have had no issues since. It's strange that the delayed start began exactly when the engine light came on. Any insights or troubleshooting steps would be greatly appreciated.

Related fault codes

P0456

Comments (6)

Anonymous 2014-12-17 11:49

If you're still using the original battery, consider replacing it now — especially if the starter is turning over slowly. While a loose gas tank cap can trigger code P0456, it's unlikely to cause slow cranking. A weak battery or poor electrical connection may be responsible for the starting delay.

Anonymous 2014-12-17 13:39

Thanks for the reply. I don’t think the starter is failing — at least not directly. The issue started after I accidentally left an interior light on overnight about two months ago, which drained my battery. I jumped it then and have had no problems since. It's strange that the delayed start began exactly when the engine light came on. Could there be a connection between the battery condition and the emission code?

Anonymous 2014-12-17 14:18

I recommend starting with a known-good battery — one that maintains at least 10.5–11 volts during cranking (before engine starts). If the voltage stays stable, check the voltage at the starter; it should be close to battery voltage, perhaps slightly lower. If both readings are normal but cranking remains weak, the starter may be failing. You mentioned a delayed start — is this due to a weak or slow crank, or just a long wait before the engine starts? A weak crank points toward electrical issues like a failing battery or starter. A strong crank with prolonged startup time might point to a different problem, possibly related to the P0456 code.

Anonymous 2014-12-17 15:08

Thanks for the clarification — yes, I do experience a very weak and slow cranking sensation, which delays engine start significantly. I’ve already opened the hood and inspected all battery connections, including the main terminal and ground strap. I’ll tighten them properly tonight after work and monitor if there’s any improvement.

Anonymous 2015-03-17 14:21

I'm experiencing a different issue — on my 2013 Hyundai Genesis Coupe, I get code B1334 related to the airbag system. Anyone know how to resolve this? It's not going out or resetting.

Anonymous 2015-03-17 15:03

DTC B1334 indicates a malfunction in the front impact sensor assembly (right front). This is a safety-related issue and should not be attempted by DIYers. I strongly recommend visiting an authorized Hyundai dealer for diagnosis and repair, as working with SRS systems carries serious risks.