P1456
DTC P1456: Leak Detected In EVAP Control System (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 these are two-trip codes. Once cleared, they cannot be reproduced in one trip. Also, certain specific driving and ambient conditions must occur before the ECM 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 there must be less than a full tank of gas. If possible, to assist in leak detection, add one 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 (the cap must be an 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.
NO - Fuel fill cap is OK. Go to step 3.
EVAP canister purge valve test
3. Disconnect the vacuum hose from the EVAP purge control solenoid 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 the 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 ECM connector A (32P).
10. Check for continuity between the EVAP canister purge valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Repair short in the wire between the EVAP canister purge valve and the ECM (A6).
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
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. With the Honda PGM Tester in the EVAP test mode, turn on the bypass solenoid, or connect ECM 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 the EVAP bypass solenoid valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Go to step 18.
NO - Repair open in wire between the EVAP bypass solenoid valve and the ECM (A3).
18. Turn the ignition switch ON (II).
19. Measure voltage between the 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-rings (B).
NO - Repair open in the wire between the EVAP bypass solenoid valve and the No.4 (7.5 A) fuse.
20. Cap the upper port (A) of the EVAP two-way valve.
21. While monitoring the FTP sensor voltage with the Honda PGM Tester, or measuring the voltage between ECM connector terminals A29 and C18, slowly pump the vacuum pump until the voltage drops to approximately 1.5 volts.
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, fuel tank pressure sensor and O-rings.
EVAP Canister Vent Shut Valve Test
22. Disconnect the vacuum hose from the EVAP canister vent shut valve (A), and connect a vacuum pump to the hose.
23. Turn the ignition switch ON (II).
24. Apply vacuum to the hose with five 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 28.
25. Turn the ignition switch OFF.
26. Disconnect the EVAP canister vent shut valve 2P connector.
27. Check for continuity between the 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 ECM connector A (32P).
29. Check for continuity between the 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 the ECM (A4).
NO - Go to step 30.
Vacuum Hoses and Connections Test
30. Perform fuel tank vapor control valve tests.
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 3 "clicks", then monitor fuel tank pressure readings with the Honda PGM Tester.
32. Start the engine. Let the engine idle for five minutes.
33. Check the FTP sensor reading.
Is the reading above 4 mm Hg pressure, below -4 mm Hg vacuum, or about 3 V?
YES - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
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 lube (F)
- Fuel tank vapor signal tube (G)
- Fuel tank vapor control vent tube (H)
- If necessary, repair or replace the parts.