OBD II Code P0456 is a generic diagnostic code that means you've got a severe leak in your evaporative emission recapture system (EVAP System). This code is, in most regards, no big deal – it's usually easy to fix & almost always something you can ignore for a short while. Read on for more context on the code & things you should know.
What does code P0456 mean on a BMW Z4?
Code P0456 means you're encountering insufficent suction within your fuel system. This is checked by a sensor connected to the powertrain control module or Engine Control Unit – computers that keep tabs on the functioning of your engine.
What causes OBD code P0456?
P0456 can be caused by a range of issues but most of the time it just means you need to replace or repair your gas cap. It's likely either unscrewed or damaged.
Other causes may include:
- A cracked hose attached to the carburetor (more common in climates with extreme temperatures)
- A cracked or damaged activated charcoal canister (This is fairly rare)
- A problem with the purge valve (These are pretty bulletproof, so this is also a rare issue)
- A damaged, stuck, or faulty vent control valve (again, quite unusual)
How can I fix P0456 on a BMW Z4?
Before you do anything else, we recommend giving your vehicle a complete OBD II scan with a tool like BlueDriver. This will give you a complete picture of every issue your vehicle is having so you aren't playing whack-a-mole with OBD codes.
First, check the gas cap – screw it in if it's not already. If it is, visually inspect the cap for wear or damage. Make sure you're using the original cap or a suitable replacement. Mismatches are a common cause of P0456.
If your gas cap is faulty & needs replacing, we recommend Amazon for their quick shipping & massive selection. You can buy a BMW Z4 gas cap here.. Make sure to purchase a cap that matches your vehicle's make, model, & year – if the fit isn't perfect it won't work.
If it's not the gas cap, what should I try next?
There's a few approaches to fixing EVAP leaks but the video below demonstrates the process on a '04 Mustang. Highly recommend watching it in full to get a feel for the steps you'll need to take if it's a hose leak.
If the issue is a cracked or otherwise damaged charcoal canister the process is extremely straightforward – you shouldn't need too much guidance to swap it out. If the issue persists & you can't figure it out, there's no shame in heading to a dealership.
Can I drive with code P0456?
OBD code P0456 is a reasonably safe code to ignore for a while because it doesn't have a dramatic effect on engine function. However, as with all codes that trigger the check engine light, you'll need to get it fixed to ensure that you don't miss a more dangerous or damaging issue when it pops up in the future.
Background on OBD code P0456
US automotive emissions regulations dating back to 1971 require that new vehicles sold in the US can't release evaporative hydrocarbon smog from the fuel system. Automakers meet this requirement by ensuring the entire path the fuel takes from tank to cylinder is completely sealed. The system operates as a sort of vaccuum that draws fuel from the tank to the engine, which helps manage fuel evaporation fumes.
One last reminder… – we hope you found this information helpful, but your vehicle's maintenance is your responsibility. If you're not sure, consult a professional mechanic.