Jeep P0456, P0457 Codes — Most Common Causes

Jeep P0456, P0457 — What to check first if you get these codes

A Jeep P0456 is defined as an EVAP PURGE SYSTEM SMALL LEAK, while a Jeep P0457 is defined as a LOOSE FUEL CAP.

Step by step procedure to diagnose Jeep P0456 trouble codes

Check for leak in the purge hose and purge valve

A stuck purge valve is a common problem on Jeeps and the cause can be a bad valve or a leaking charcoal canister that spews charcoal particles into the purge hose. Start by removing the purge valve and checking for charcoal particles. If you see those, the canister is damaged and must be replaced. If the valve and hose are clean, use a handheld vacuum pump and jumper power to activate the purge valve while under vacuum and no vacuum to see if it’s opening and closing properly and holding vacuum.

MOPAR 4891739AA purge valve

With the purge valve closed, this hose should hold vacuum.

If it doesn’t hold vacuum, disconnect the hose at the purge valve and plug it. Then re-test the hose. If it holds vacuum, the hose is good and the problem is the purge valve. Test the purge valve to see if it holds vacuum. Replace the parts as needed.

If not leaks are found or the line holds vacuum, the problem is with the charcoal canister/Evaporative System Integrity Monitor (ESIM). Replace it. This unit has a very high failure rate.

Evaporative System Integrity Module Detector 4861959AC

Step by step procedure to diagnose Jeep P0457 trouble codes

Chrysler had had big problems with the Evaporative System Integrity Module Detector (ESIM). Remove the gas cap and inspect the gasket for tears or abrasion. Check the filler neck for rust/corrosion. Replace the gas cap

MOPAR 52030377AB gas cap

NOTE: A P0457 trouble code can’t be reset by the scan tool. Instead, the PCM must complete a drive cycle where it performs a leak test. The gas cap must pass the leak test in order to shut off the light can clear the p0457 trouble code.

If the gas cap is in good condition, chances are high that the ESIM is bad. It has a pretty high failure rate. It’s not an expensive part, so if you want to fire the parts canon, it might be worth a shot.

P0457 drive cycle: Drive the vehicle for 16-20 miles. Then shut off the vehicle off and park it overnight. If the new gas cap fixes the problem, the gas cap light will shut off on the next key cycle. If the light does not go off, recheck for fault codes.

©, 2022 Rick Muscoplat