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
This is a two-trip code; once cleared, it 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 code.
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 fuel. 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
Check the fuel fill cap. It must be a gray or black OEM cap and be tightened at least 3 "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.
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 - The fuel fill cap is OK. Go to step 3.
EVAP Bypass Solenoid Valve Test
Disconnect the vacuum hose from the EVAP two way valve (A), and connect a vacuum pump to the hose.
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.
Turn the ignition switch ON (II).
Apply vacuum to the hose.
Does the valve hold vacuum?
YES - Go to step 7.
NO - The EVAP bypass solenoid valve/EVAP two way valve is OK. Go to step 12.
Turn the ignition switch OFF.
Disconnect the EVAP bypass solenoid valve 2P connector.
Check for continuity between EVAP bypass solenoid valve 2P connector terminal No.2 and body ground.
Is there continuity?
YES - Go to step 10.
NO - Repair open in wire between the EVAP bypass solenoid valve and ECM/PCM (A3).
Turn the ignition switch ON (II)
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 the O-rings (B).
NO - Repair open in the wire between the EVAP bypass solenoid valve and No.6 ECU (ECM/PCM) CRUISE CONTROL (15A) fuse.
Plug the upper port (A) of the EVAP two-way valve.
While monitoring the FTP sensor voltage with the Honda PGM Tester, or measuring the voltage between PCM connector terminals A29 and C15, slowly pump vacuum 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 - The EVAP bypass solenoid valve/EVAP two-way valve is OK.
NO - Repair leakage from the EVAP bypass solenoid valve, EVAP two-way valve, FTP sensor, or O-rings.
Vacuum Hoses and Connections Test
Perform the fuel tank vapor control valve test.
Is the fuel tank vapor control valve normal?
YES - Go to step 15.
NO - Replace the fuel tank vapor control valve.
Tighten the fuel cap 3 "clicks", then monitor fuel tank pressure readings with the Honda PGM Tester.
Start the engine. Let the engine idle for 5 minutes.
Check the FTP sensor reading.
Is the reading above 0.53 kPa (0.16 in. Hg 4 mm Hg) pressure, or approx 3 V?
YES - Substitute a known-good ECM/PCM and retest. If the symptom/indication goes away, replace the original ECM/PCM.
NO - Check the following parts for leaks:
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)
EVAP two-way valve (I)
FTP sensor (J)
Repair or replace any leaking parts.
© 2013 ALLDATA LLC. All rights reserved. Terms and Conditions
Please consider a to help us answer more questions.
Friday, March 8th, 2013 AT 1:35 AM