DTC P0455: EVAP System Large Leak Detected; DTC P0456: EVAP System Very Small Leak Detected

NOTE: The fuel system is designed to allow specified maximum vacuum and pressure conditions. Do not deviate from the vacuum and pressure tests as indicated in these procedures. Excessive pressure/vacuum would damage the EVAP components or cause eventual fuel tank failure.

Special Tools Required

Vacuum pump/gauge, 0-30 in.Hg, Snap-on YA4000A or equivalent, commercially available

NOTE:

Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
Fresh fuel has a higher volatility that will create greater pressure/vacuum. The optimum condition for testing is less than a full tank of fresh fuel. If possible, to assist in leak detection, add 1 gallon of fresh fuel to the tank (as long as it will not fill the tank), just before starting these procedures.

Check the fuel fill cap (the cap must say "TIGHTEN TO CLICK"). It should turn 1/4 turn after it's tight, then it clicks.
Is the correct fuel fill cap installed and properly tightened?

YES - Go to step 2.

NO - Replace or tighten the cap, then go to step 26.
Check the fuel fill cap seal (A) and the fuel fill pipe mating surface (B). Verify that the fuel fill cap tether cord (C) is not caught under the cap.

Fig 1: Checking Fuel Fill Cap Seal And Mating Surface
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is the fuel fill cap seal missing or damaged, is the fuel fill pipe damaged, or is the tether cord caught under the cap?

YES - Replace the fuel fill cap or the fuel fill pipe, then go to step 26.

NO - Go to step 3.
Turn the ignition switch ON (II).
Clear the DTC with the HDS.
Do the EVAP FUNCTION TEST in the INSPECTION MENU with the HDS.
Is the result OK?

YES - Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the FTP sensor, the EVAP canister purge valve, or the EVAP canister vent shut valve and the ECM/PCM.

NO - Go to step 6.
Turn the ignition switch OFF.
Check for a poor connection or damage at the fuel tank vapor recirculation tube.
Is the tube OK?

YES - Go to step 8.

NO -
- Replace the fuel tank vapor recirculation tube, then go to step 26.
- If necessary, replace the fuel tank (see FUEL TANK REPLACEMENT ), then go to step 26.
Disconnect the fuel tank vapor recirculation tube (A) from the EVAP canister (B), and plug the EVAP canister port (C).

Fig 2: Disconnecting Fuel Tank Vapor Recirculation Tube From EVAP Canister
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Disconnect the vacuum hose (purge line) (A) from the EVAP canister purge valve (B) in the engine compartment, and connect a vacuum pump/gauge, 0-30 in.Hg, to the vacuum hose as shown.

Fig 3: Disconnecting Vacuum Hose (Purge Line) And EVAP Canister Purge Valve
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch ON (II).
Select EVAP CVS ON in the INSPECTION MENU with the HDS.
Apply vacuum to the hose until the FTP reads 1.90 V (-0.59 inHg, -15.1 mmHg).
NOTE: Be careful not to exceed the vacuum. If you do, the FTP sensor can be damaged.
Select EVAP PCS OFF in the INSPECTION MENU with the HDS and disconnect a vacuum pump/gauge, 0-30 inHg, from the hose.
Monitor the FTP SENSOR in the DATA LIST for 1 minute with the HDS.
Does the voltage increase more than 0.2 V (0.1 inHg, 2.5 mmHg)?

YES - Go to step 15.

NO - Go to step 22.
Turn the ignition switch to LOCK (0).
Reinstall the EVAP canister purge valve (A) to the throttle body (B) with a new O-ring, and disconnect the vacuum hose (EVAP canister side) (C) from the EVAP canister purge valve, then connect a vacuum pump/gauge 0-30 inHg, to the vacuum hose as shown.
Turn the ignition switch to ON.
Apply vacuum to the hose until the FTP reads 1.90 V (-0.59 inHg, -15.1 mmHg).
NOTE: Be careful not to exceed the vacuum. If you do, the FTP sensor can be damaged.
Monitor the FTP SENSOR in the DATA LIST for 1 minute with the HDS.
Does the voltage increase more than 0.2 V (0.1 inHg, 2.5 mmHg)?

YES - Replace the EVAP canister purge valve, then go to step 29.

NO - Go to step 21.
Check for a loose or damaged EVAP canister purge line between the EVAP canister and the EVAP canister purge valve, or check for a leaking the EVAP canister.
Are the line and the EVAP canister OK?

YES - Replace these parts, then go to step 25:
- FTP sensor O-ring
- EVAP canister vent shut valve case and O-ring
- EVAP canister
NO - Reconnect or repair the EVAP canister purge hose, then go to step 25.
Turn the ignition switch to LOCK (0).
Reconnect the fresh air hose (A) to the EVAP canister (B).
Remove the EVAP canister purge valve (A) from the throttle body (B) without disconnecting the vacuum hose (C) and the EVAP canister purge valve 2P connector (D), then connect a vacuum pump/gauge, 0-30 inHg, to the purge valve as shown.
Turn the ignition switch ON (II).
Select EVAP CVS ON in the INSPECTION MENU with the HDS.
Apply vacuum to the EVAP system until the FTP reads 1.90 V (-0.59 inHg, -15.1 mmHg).
NOTE: Be careful not to exceed the vacuum. If you do, the FTP sensor can be damaged.

Fig 4: Disconnecting Fresh Air Hose From EVAP Canister
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Monitor the FTP SENSOR in the DATA LIST for 1 minute with the HDS.
Does the voltage increase more than 0.2 V (0.1 inHg, 2.5 mmHg)?

YES - Replace the EVAP canister vent shut valve, then go to step 29.

NO - Go to step 27.
Select EVAP CVS OFF in the INSPECTION MENU with the HDS.
Check these parts for looseness or damage:
- Fuel fill Pipe
- Fuel vapor return pipe
Are the parts OK?

YES - Check the fuel tank unit base gasket, and check the fuel tank, then go to step 29.

NO - Repair or replace the damaged part(s), then go to step 29.
Reconnect all hoses and connectors.
NOTE: When you install the EVAP canister purge valve to the throttle body, use a new O-ring.
Turn the ignition switch to ON (II).
Reset the ECM/PCM with the HDS.
Do the ECM/PCM idle learn procedure.
Do the EVAP FUNCTION TEST in the INSPECTION MENU with the HDS.
Is the result OK?

YES - Troubleshooting is complete.

NO - Check for poor connections or loose terminals at the FTP sensor, the EVAP canister purge valve, the EVAP canister vent shut valve, and the ECM/PCM, then go to step 1.