Check engine light, code P0456 after transmission was replaced?

Tiny
LLEWYN
  • MEMBER
  • 2005 FORD FOCUS
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
I just had my transmission replaced. The mechanic said he checked everything and nothing else was wrong. When he called to say it was ready he said something about the head gasket but didn't mention it when I picked up my car. Now the check engine light is on, I did an electrical scan at an auto part store and it came back with P0456.
Tuesday, October 7th, 2025 AT 3:13 PM

2 Replies

Tiny
JONNYB1963
  • MECHANIC
  • 263 POSTS
Hi there, the P0456 is an "EVAP" code that deals with the evaporative emissions control system of the vehicle. It can be caused by a leaky fuel cap seal which is the most common cause I have found but there are other culprits.

-Very small holes, cracks or cuts in the fuel vapor hoses or tubes (sometimes they get dry-rot)
-Loose fuel vapor hose or tube connections to the EVAP system components
-EVAP system component seals leaking

What to look for:
1. Check for a missing fuel filler cap or the integrity of the cap (or the flap if you have a capless version, verify the capless fuel tank filler pipe is sealed correctly. Install and remove the supplemental fueling adapter five times in the capless fuel tank filler pipe to clear anything that might be on the seal.
2. Check for loose or damaged vapor recovery hoses.
3. Visually inspect the EVAP canister inlet port, its vent valve filter, and the vent hose assembly for any contamination or dirt.

Let me know what you find!
Was this
answer
helpful?
Yes
No
Tuesday, October 7th, 2025 AT 3:52 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Please respond
Was this
answer
helpful?
Yes
No
Tuesday, October 14th, 2025 AT 12:58 PM

Please login or register to post a reply.