Fixing a p0455 – p0442 on a 2003 Jeep Cherokee

The preliminary install started much like any other. Check Engine Light is on, plug in my incredibly good priced ElmScan 5 Compact USB OBD-II Scan Tool & OBDWiz Engine Diagnostic Software (423001) from Amazon (affiliate link) to pull the code and see what pops up.

p0455 – evap emmisions system – large leak
p0442 – evap emmissions system – small leak

Ok so now what? After some quick searches, it seems to be caused from a cracked Evap line or a bad gas cap. Well, the gas cap was replaced recently so time to get dirty!



Sure enough, some bad vacuum lines. 4 feet of 1/4″ vacuum line is enough to pretty much replace all the lines in the rear and about 2 inches of 5/16″ line for the short connection under the hood.

Repair procedure:

1. Remove the left rear wheel.
2. Remove the wheelhouse splash shield (five plastic rivets P/N 34201631) to gain access
3. Remove the hose at the top rear of the evaporative canister to ease vent valve removal.
4. Remove all clamps and all hoses attached to the vent valve.
5. Install new vent valve. Ensure all hoses, clamps and the vacuum hose to the top of the vent valve are securely attached.
6. Attach the hose at the top rear of the evaporative canister.
7. Install wheelhouse splash shield using five plastic rivets.
8. Install left rear wheel (WJ only).
9. Lower vehicle.

Once installed, start the car, listen for air leaks and plug in the scanner. To reset the ECU, turn the car on without starting it and clear the codes with the scanner. Start your Jeep and let it run for a little while to see if the code gets stored. Prior to fixing the line, it would flash the code in minutes. If you don’t have a scanner, reset the ECU by unhooking the battery during the install. It could take a few drive cycles before you know for sure.

That’s it, hopefully this helps.