P1456
DTC P1456: EVAP Control System Leakage (fuel tank system)
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 A973X-041-XXXXX
Please note that this is a 2 trip code, once cleared, they cannot be reproduced in 1 trip. Also, certain specific driving and ambient conditions must occur before the PCM will complete the system checks. Additional test drives may still not meet the specific conditions needed to reproduce the codes.
Therefore, follow these troubleshooting procedures carefully to ensure the integrity of the system and to confirm the cause of the problem or code.
NOTE: Fresh fuel has a higher volatility that will create greater pressure/vacuum. The optimum condition for testing is fresh fuel, and must be less than a full tank of gas. 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.
Fuel Fill Cap Check
1. Check the fuel fill cap. It must be a gray or black OEM cap and be tightened at least three "clicks" to properly seal the system.
Is proper fuel fill cap installed and properly tightened?
YES - Go to step 2.
NO - Replace or tighten the cap.
2. Check the fuel fill cap seal.
Is the fuel fill cap seal missing or damaged?
YES - Replace the fuel fill cap (gray or black colored cap).
NO - Fuel fill cap is OK. Go to step 3.
EVAP Canister Purge Valve Test
3. Disconnect the vacuum hose from the EVAP canister purge valve (A), and connect a vacuum pump to the hose.
4. Turn the ignition switch ON (II).
5. Apply vacuum to the hose.
Does the valve hold vacuum?
YES - EVAP canister purge valve is OK. Go to step 11.
NO - Go to step 6.
6. Turn the ignition switch OFF.
7. Disconnect the EVAP canister purge valve 2P connector.
8. Check for continuity between EVAP canister purge valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Go to step 9.
NO - Replace the EVAP canister purge valve.
9. Disconnect the PCM connector A (32P).
10. Check for continuity between EVAP purge control solenoid valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Repair short in the wire between the EVAP purge control solenoid valve and PCM (A6).
NO - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
EVAP Bypass Solenoid Valve Test
11. Disconnect the vacuum hoses from the EVAP two way valve (A), and connect a vacuum pump to the hose.
12. Connect the PCM connector terminal A3 to body ground with a jumper wire.
13. Turn the ignition switch ON (II).
14. Apply vacuum to the hose.
Does the valve hold vacuum?
YES - Go to step 15.
NO - Go to step 20.
15. Turn the ignition switch OFF.
16. Disconnect the EVAP bypass solenoid valve 2P connector.
17. Check for continuity between EVAP bypass solenoid valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Go to step 8.
NO - Repair open in wire between the EVAP bypass solenoid valve and PCM (A3).
18. Turn the ignition switch ON (II).
19. Measure voltage between EVAP bypass solenoid valve 2P connector terminal No.1 and body ground.
Is there battery voltage?
YES - Replace the EVAP bypass solenoid valve (A) and O-ring (B).
NO - Repair open in the wire between the EVAP bypass solenoid valve and No.6 ECU (PCM) CRUISE CONTROL (15 A) fuse.
20. Plug the upper port (A) of the EVAP two way valve.
21. While monitoring the Fuel Tank Pressure (FTP) sensor voltage with the Honda PGM Tester, or measure the voltage between PCM connector terminals A29 and C18, slowly pump the vacuum pump until the voltage drops to about 1.5 V.
Does the voltage drop to 1.5 V and hold for at least 20 seconds?
YES - EVAP bypass solenoid valve/EVAP two way valve is OK. Go to step 22.
NO - Repair leakage from EVAP bypass solenoid valve, EVAP two way valve, FTP sensor and O-rings.
EVAP Canister Vent Shut Valve Test
22. Disconnect the vacuum hose from the EVAP canister filter (A), and connect a vacuum pump to the hose.
23. Turn the ignition switch ON (II).
24. Apply vacuum to the hose with 5 strokes of the pump.
Does the valve hold vacuum?
YES - Go to step 25.
NO - EVAP canister vent shut valve is OK. Go to step 30.
25. Turn the ignition switch OFF.
26. Disconnect the EVAP canister vent valve 2P connector.
27. Check for continuity between EVAP canister vent shut valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Go to step 28.
NO - Replace the EVAP canister vent shut valve (A) and O-ring (B).
28. Disconnect the PCM connector A (32P).
29. Check for continuity between EVAP canister vent shut valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Repair short in the wire between the EVAP canister vent shut valve and PCM (A4).
NO - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
Vacuum Hoses and Connections Test
30. Perform fuel tank vapor control valve tests. Testing and Inspection
Did the fuel tank vapor control valve test normal?
YES - Go to step 31.
NO - Replace the fuel tank vapor control valve.
31. Tighten the fuel cap three "clicks", then monitor the FTP readings with the Honda PGM Tester.
32. Start the engine. Let the engine idle for 5 minutes.
33. Check the FTP sensor readings.
Is the reading above 4 mm Hg pressure or below -4 mm Hg vacuum?
YES - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
NO - Check the following parts for leaks:
- Fuel tank (A)
- Fuel fill cap (B)
- Fuel fill pipe (C)
- Fuel tank vapor control valve (D)
- Fuel tank vapor recirculation valve (E)
- Fuel tank vapor recirculation tube (F)
- Fuel tank vapor signal tube (G)
- Fuel tank vapor vent tube (H)
If necessary, repair or replace the parts.
DTC P1456 Still Set? Test For Internal Leaks
Leak Testing For DTC P1456
1. Turn the ignition switch ON (II).
2. Use the Honda PGM tester in the EVAP test mode to turn on the EVAP bypass solenoid valve.
Clamp the vacuum hose between the two-way valve port.
3. Disconnect the vacuum hose between the canister and the two-way valve at the two-way valve port.
4. Attach a hand vacuum pump to the canister port of the two-way valve, and apply vacuum until the FTP sensor voltage reads 2.1 V (You'll notice that it takes very little vacuum).
5. Unplug the 2P connector from the bypass solenoid valve.
6. Detach the vacuum pump.
7. Watch the FTP sensor voltage. If the voltage rises above 2.15 V in 20 seconds, replace the two-way valve and the bypass solenoid valve.