4 Causes and Fixes for a Jeep P0456 Code

The EVAP system is a part of the emissions which help to stop gas vapors from venting into the atmosphere.

What is a P0456 Jeep Code?

A Jeep P0456 OBDII error code is a Small Leak Detected in the EVAP System.

The EVAP system was created to stop gas vapors from leaking into the atmosphere.

This helps reduce emissions and gives a vehicle better fuel efficiency.

If a component in the EVAP system fails or there is a leak, the ECM will give a P0456 error code.

4 Causes and Fixes Jeep P0456 Code

1. Bad Gas Cap


If the gas cap is not tightened correctly or is not sealing, it will cause a small leak and can give a P0456 code.

Check that the gas cap is on tight and examine if the rubber seal is broken.

Sometimes debris can stop a gas cap from making a good seal.

Some Jeep owners will buy a new gas cap to rule it out as a possible cause.

If you do, buy a new gas cap, and be sure it is made for your Jeep year and model, as there can be differences.

2. Faulty Purge Valve



The purge valve solenoid opens and closes to send the gas vapors into the engine to be burnt away.

It will open when an engine is running and close when the engine is shut off.

If it fails, it can cause EVAP errors such as a P0456 code.

A quick method to test the EVAP purge valve is to see if the hose going back to the charcoal canister has a vacuum when the engine is running.

3. Leak In EVAP System


There may be a leak in the EVAP system, such as a hose or other component.

Leaks are often found with a smoke machine.

A smoke machine will send smoke into the EAVP system and will come out where the leak is located.

4. Faulty Charcoal Canister or Vent Solenoid

The charcoal canister is located near the gas tank and does a few things, mainly holding the gas vapors when the engine is not running.

A vent valve is located on the Charcoal Canister and lets the ECM test the EVAP system by opening and closing when a signal is sent.

The vent valve can fail, or a hose attached to the charcoal canister can be leaking.

If all other components test good testing the charcoal canister and vent valve would be next.

Summary
A Jeep that has an OBDII P0456 has a problem with the EVAP system.

The vehicle is usually still derivable but will get slightly worse gas mileage and will not pass a smog test.

Common fixes are the gas cap bad or a bad vent solenoid.

If the cause is hard to find, there likely is a leak in the system; a smoke machine will need to be used to find the leak.