Fuel Tank System / Leak Detected
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/PCM will complete the system checks. Additional test drives may still not meet the specific conditions needed to reproduce the codes.
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 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. It must be a gray OEM cap and be tightened at least three "clicks" to properly seal the system.
Is the correct 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 colored cap).
NO-Fuel fill cap is OK. Go to step 3.
EVAP purge control solenoid 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 purge control solenoid valve is OK. Go to step 11.
NO-Go to step 6.
6. Turn the ignition switch OFF.
7. Disconnect the EVAP purge control solenoid valve 2P connector.
8. Check for continuity between the EVAP purge control solenoid valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES-Go to step 9.
NO-Replace the EVAP purge control solenoid valve .
9. Disconnect the ECM/PCM connector A(32P).
10. Check for continuity between the EVAP purge control solenoid valve 2P connector terminal No.2 and body ground.
Is the continuity?
YES-Repair short in the wire between the EVAP purge control solenoid valve and ECM/PCM (A6).
NO-Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.
Diagnostic Strategies
EVAP Bypass Solenoid Valve Test
11. Disconnect the vacuum hose from the EVAP two-way valve (A), and connect a vacuum pump to the hose.
12. Connect the ECM/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-The EVAP bypass solenoid valve/EVAP two- way valve is OK. Go to step 22.
15. Turn the ignition switch OFF.
16. Disconnect the EVAP bypass solenoid valve 2P connector.
17. Check for 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 ECM/PCM (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 No.6 ECU (ECM/PCM) CRUISE CONTROL (15 A) fuse.
20. Plug the upper port (A) of the EVAP two-way valve.
21. While monitoring the 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 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 Control Canister Vent Shut Valve Test
22. Disconnect the vacuum hose from the EVAP control canister filter (A), and connect a vacuum pump to the hose.
23. Turn the ignition switch ON (II).
24. Apply vacuum to the hose.
Does the valve hold vacuum?
YES-Go to step 25.
NO-EVAP control canister vent shut valve is OK. Go to step 30.
25. Turn the ignition switch OFF.
26. Disconnect the EVAP control canister vent valve 2P connector.
27. Check for continuity between the EVAP control canister vent shut valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES-Go to step 28.
NO-Replace the EVAP control canister vent shut valve (A) and O-ring (B).
28. Disconnect the ECM/PCM 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 control canister vent shut valve and ECM/PCM (A4).
NO-Substitute a known-good ECM/PCM and recheck.If the symptom/indication goes away, replace the original ECM/PCM.
Diagnostic Strategies
Vacuum Hoses and Connections Test
30. Tighten the fuel cap three "clicks", then monitor the fuel tank pressure readings with the Honda PGM Tester.
31. Start the engine. Let the engine idle for five minutes.
32. Check the Fuel Tank Pressure sensor readings.
Is the reading above 4 mm Hg pressure or below 4 mmHg vacuum?
YES-Substitute a known-good ECM/PCM and retest. If the symptom/indication goes away, replace the original ECM/PCM.
Diagnostic Strategies
NO-Check the following parts for leaks:
- Fuel tank (A)
- Fuel fill cap (B)
- Fuel fill pipe (C)
- ORVR vent shut valve (D)
- ORVR vapor recirculation valve (E)
- ORVR vapor recirculation tube (F)
- ORVR signal tube (G)
- ORVR vapor vent tube (H)
- EVAP two-way valve (I)
- Fuel tank pressure sensor (J)
- If necessary, repair or replace the parts.