HONDA DTC P1457含义

闲云野鹤

https://www.engine-codes.com/p1457_honda.html
P1457 HONDA - Evaporative Emissions Control System Leakage EVAP Canister SystemRepair Importance Level: 3/3
Repair Difficulty Level: 3/3  

Possible causes
Missing Fuel cap
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close
Foreign matter caught in fuel filler cap
EVAP purge control solenoid
EVAP canister
Fuel tank pressure sensor

P1457 won't make the car run bad at all. It just means the EVAP canister & the related system of hoses & valves isn't airtight like it should be.

Check this stuff in this order. As soon as you find something that doesn't behave like it should, fix or replace it. Then hope it was the only thing wrong with the system...


Some background for the electrical troubleshooting:
All the solenoid valves have constant +12v supply from the main relay. When the ECM wants to energize a valve, it closes the ground side of it's circuit. If the +12v supply is broken, then the ECM can't energize the valve. If the wire to the ECM is shorted to ground, then the valve is energized even when the ECM doesn't want it to be.


EVAP Purge Control valve - between intake manifold & valve cover.
Valve should be normally closed, so it will hold vacuum when it's not energized. Ground is supplied by pin A6 of the ECM to open the valve. So jumper pin A6 to ground, turn on the ignition, and check again - this time it should NOT hold vacuum.
EVAP 2-way valve - underneath the car roughly under the left-rear seat. It's a little can with 3 hose barbs & a solenoid valve attached to it. Leave the connection on top, disconnect both on the side, attach MityVac to lower one. Normally closed, it should hold vacuum when the solenoid is not energized. When the solenoid valve is energized, it should not hold vacuum.


************ THANKS to rjpjnk for the following clarification about this valve.
The 2 way valve is complicated. It should hold vacuum on the lower port when the solenoid is *not* energized. The solenoid when energized provides a passageway to bypass the normal path between the upper port and the lower port. That's why it is called a "bypass solenoid" btw.


The upper port of this wretched valve from pluto is actually designed to open to pass vacuum or pressure to the lower port when the vacuum or pressure exceeds a certain threshold (a kind of hysteresis effect). The slight resistance to flow is what allows a certain design pressure to remain in the fuel tank. Once this is exceeded, the excess pressure (fuel vapor) bleeds over to the canister side. At any time, the ECM can force this to happen by activating the bypass solenoid. It does exactly this during the p1456/p1457 diagnostic tests. The upper side port is always connected to the top port (the third leg of this beast) which is connected directly to the FTP (fuel tank pressure sensor). Did you know the FTP sensor is not in the fuel tank? ;-)
************


EVAP Canister Vent Shut valve - attached to the charcoal canister underneath the car.
Normaly open - when ECM closes pin A4 to ground, it should hold vacuum.


EVAP Charcoal Canister - the big can under the car, about under the left-rear seat.
Leak test: Connect all the hoses together, plug the Vent Shut valve, connect the MityVac. Pump vacuum while watching the fuel tank pressure (FTP) sensor. You can read FTP sensor voltage with a scan tool, or use a voltmeter between pins A29 & C18 at the ECM. Pump down to 1.5v & it should hold that vacuum for at least 20 seconds.


EVAP 2-way valve vacuum & pressure test.
If you get this far you'll want the manual for a good picture of how to connect the hoses. Keep pumping the vacuum pump & it should stabilize between 6 & 16 mm Hg of vacuum. Then pump pressure, it should stabilize at 8 mm Hg or more of pressure.


Then there's a test of the ORVR Vent Shut valve, which is located on top of the gas tank. You check vacuum & pressure at a couple hoses alongside the fuel filler pipe. If the valve is bad you drop the gas tank to replace it...




https://www.fiix.io/car-advice/a ... anister-purge-valve
The canister purge valve, also commonly referred to as the purge valve, is an important component of your Evaporative Emission Control (EVAP) system. This system restricts the fuel vapours created in your fuel tankfrom escaping into the atmosphere by trapping them in a charcoal canister. When your engine begins to run at regular speed, the EVAP system slowly allows these vapours to be released into your engine, which burn like regular fuel. The flow of these vapours is controlled by your canister purge valve, which regulates when and how much of these vapours enter your engine.
The canister purge valve is electrically operated, and is also referred to commonly as a solenoid. The most common purge valve issues are when the purge valve is stuck open or closed, or does not open at the proper time. The symptoms are listed below that may indicate your canister purge valve is not functioning properly.
1. Check Engine Light Is On
The first sign of trouble for your canister purge valve is the check engine light. Your canister purge valve is controlled by your car’s computer, which allows it to monitor its performance. If your car’s computer detects higher or lower than expected purging from the valve, it will illuminate the check engine light. Common error codes include P0441 and P0446, as well as other EVAP codes. If your check engine light turns on, make sure to bring your car to a certified mechanic who can help diagnose the problem.
2. Lower Gas Mileage
If your canister purge valve is not opening properly, it may adversely impact your gas mileage. The reason for this is that the vapours that your car regularly uses in combustion will find the EVAP canister and eventually be vented to the environment, meaning that you will lose a portion of the fuel regularly used in burning.
3. Engine Problems
If your canister purge valve is stuck open, however, it creates a vacuum leak that can affect your engine adversely. Simply put, air will be allowed to enter the engine in a quantity that is not predicted by your car’s computer. This will change the car’s air to fuel ratio, and can cause rough idling (car feels rough and bouncy when the engine is running), as well as difficulty starting. If experienced in tandem, there is a high likelihood of a failing canister valve, or some other part of the EVAP system.

P1457与油耗无关，只与那三个电磁阀有关，最可能坏的就是那个最贵的shut off valve. 不管哪个电磁阀坏，结果只能是该排入活性炭盒子的油气仍然留在油路中。