Rick's Free Auto Repair Advice

P0456 Kia

Fix P0456 Kia

A P0456 Kia trouble code indicates a small leak in the evaporative emissions system. See this post to understand how evap systems work in general. In the case of the P0456 Kia trouble code, the problem is usually caused by a back canister closed valve or a leaking charcoal canister.

Here’s how the system works. To conduct an evap integrity test, the PCM closes the Canister Close Valve (CCV). It’s an electric solenoid valve located at the charcoal canister. The CCV valve opens during a canister purge to allow fresh air into the canister. During the test, the valve must close to seal off the evaporative emission system.

Once the CCV closes, the PCM opens the purge control valve (PCSV) to allow the engine vacuum to put the canister and fuel tank under engine vacuum. The PCM then watches the fuel tank pressure sensor and leaves the purge valve open until the vacuum reaches a preset level. Then it closes the purge valve. If the signal from the fuel tank pressure sensor rises at a certain rate and holds that value once the purge valve is closed, the system passes.

If the vacuum doesn’t rise at the preset rate or the fuel system doesn’t hold vacuum, the PCM will set either a P0442 or P0456 trouble code.

Test for P0456 Kia

You’ll need a hand held vacuum pump to test the CCV valve. Apply vacuum to the valve when it’s in the closed position. See if the valve holds vacuum. If it leaks, that’s the likely cause of the P0456 Kia trouble code. If it does hold vacuum then the leak is elsewhere. To test the canister for integrity, perform a simulation test.

Locate the blue wire at the CCV valve and ground it. That will close the CCV and seal off fresh air. Then start the engine and operate the purge valve. That will pull a vacuum on the system. Using a scan tool or multimeter, check the fuel tank pressure sensor reading. If should rise to around 3-volts. Close the purge valve and watch the readings from the fuel tank pressure sensor. It should hold steady or fall no lower than 1.5-volts. If it falls below that, there’s a leak, usually in the canister. But the leak could also be from the fuel cap or filler pipe.

©, 2020 Rick Muscoplat

Posted on by Rick Muscoplat

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