Possible causes

– Missing Fuel cap
– Incorrect fuel filler cap used
– Fuel filler cap remains open or fails to close
– Foreign matter caught in fuel filler cap

Tech notes

Usually loose or bad fuel tank filler cap will triggered this codes. Retight fuel tank filler cap and erase code to repair problem.

There is a Honda factory service bulletin with information on how to diagnose the P1456 on the following Honda models:
1998 Honda Accord
1999 Honda Accord
2000 Honda Accord
1998-2000 Honda Accord Factory Service Bulletin OBDII Code p1456

When is the code detected?

The P1456 code is detected when the EVAP system has a very small leak.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Possible a noticeable fuel odor caused by the release of fuel vapors

P1456 HONDA Description

The evaporative emission (EVAP) control system stores fuel vapor from the fuel tank in the EVAP canister temporarily to prevent it from escaping to the atmosphere and to enable it to be drawn into the engine by intake manifold vacuum and burned. In addition, the onboard refueling vapor recovery system (ORVR) stores fuel vapor generated when refueling in the EVAP canister.
The EVAP control system leak detection method improves the accuracy and frequency of the detection by determining faulty components and vapor leakage for each part. The EVAP control system (from the purge valve to the fuel tank) is divided into two parts. One is the “EVAP Canister Side” (from the EVAP two way valve to the purge valve) and the other is the “Tank Side” (from the EVAP two way valve to the fuel tank). There is 0.04 inch leak detection and 0.02 inch leak detection. If the 0.04 inch leak detection results are OK, the 0.02 inch leak detection runs.

HONDA Technical Service Bulletins for P1456 code