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Evaporative Emissions System - Small leak detected
What does that mean?
The Powertrain Control Module (PCM) at different times performs various tests on the EVAP system. OBD II Enhanced EVAP systems are in place to keep fuel tank vapors from venting into the atmosphere, and instead purges them into the engine to be burned. Regular pressure tests are conducted by the PCM to monitor the sealed system for leaks. The PCM monitors the EVAP system pressure by watching the Fuel tank pressure sensor (FTP). When the sensor indicates a small leak in the EVAP system, this code is set.
Potential Symptoms
There will likely be no noticeable symptoms other than the Malfunction Indicator Lamp (MIL). This is because the EVAP system is a closed system and only controls fuel tank vapors, not engine management.
Causes
Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause:
* A small leak in any of the EVAP hoses or fuel tank hoses
* A small leak in the purge valve or vent valve
* The EVAP Canister may be leaking
Possible Solutions
First, using a scan tool activate the vent solenoid, sealing the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the number will stay consistent. If is isn't, the pressure sensor will show that as well. If the system slowly leaks, use a smoke machine and watch for smoke exiting the system at any EVAP component. Any where there is smoke exiting the system, that is the faulty component. Do not pressurize the EVAP system with air pressure. Doing so can damage the purge and vent solenoids in the system.
Evaporative Emissions System - Small leak detected
What does that mean?
The Powertrain Control Module (PCM) at different times performs various tests on the EVAP system. OBD II Enhanced EVAP systems are in place to keep fuel tank vapors from venting into the atmosphere, and instead purges them into the engine to be burned. Regular pressure tests are conducted by the PCM to monitor the sealed system for leaks. The PCM monitors the EVAP system pressure by watching the Fuel tank pressure sensor (FTP). When the sensor indicates a small leak in the EVAP system, this code is set.
Potential Symptoms
There will likely be no noticeable symptoms other than the Malfunction Indicator Lamp (MIL). This is because the EVAP system is a closed system and only controls fuel tank vapors, not engine management.
Causes
Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause:
* A small leak in any of the EVAP hoses or fuel tank hoses
* A small leak in the purge valve or vent valve
* The EVAP Canister may be leaking
Possible Solutions
First, using a scan tool activate the vent solenoid, sealing the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the number will stay consistent. If is isn't, the pressure sensor will show that as well. If the system slowly leaks, use a smoke machine and watch for smoke exiting the system at any EVAP component. Any where there is smoke exiting the system, that is the faulty component. Do not pressurize the EVAP system with air pressure. Doing so can damage the purge and vent solenoids in the system.
If you don't have tools, replace the gas cap next, and inspect the filler neck (especially the surface that seals against the gas cap) for rust.
Small leaks are hard to find even with proper tools (smoke machine) so unless you see cracked gasket, rusted lines, loose connections, you are probably out of luck, and only thing left is throwing parts at it.
I would recommend brand new OEM gas cap - if you buy anything else, and then go to some shop to let them diagnose the problem, they will probably throw gas cap at it right away.
If you don't have tools, replace the gas cap next, and inspect the filler neck (especially the surface that seals against the gas cap) for rust.
Small leaks are hard to find even with proper tools (smoke machine) so unless you see cracked gasket, rusted lines, loose connections, you are probably out of luck, and only thing left is throwing parts at it.
I would recommend brand new OEM gas cap - if you buy anything else, and then go to some shop to let them diagnose the problem, they will probably throw gas cap at it right away.
Thanks, yeah I was trying to avoid throwing parts at it. I replaced the gas cap with a new aftermarket one when this first started. When the light back I changed the purge valve. I did notice that it was saying large leak and small then after purge valve it has just been the small leak. Do you think it's worth trying an oem gas Cap or changing canister if I don't see anything out of the ordinary ?
Without smoke machine and actually finding the leak I can't really say anything. Even with the smoke machine, sometimes finding the leak in evap is really hard.
I don't really trust aftermarket parts. Especially recently when we had bunch of cars coming back with faulty new sensors / coils / etc. I don't know what's happening but if it's more complicated than brakes we try to visit the dealer and get OEM parts.
If you have spare time, you could get a hand vacuum pump, something like:
That would allow you to test the evap parts. For example checking if purge solenoid leaks or hold vacuum, and if it opens when applied 12v (for a very brief moment)(or even 9v battery should work).
If you get to the canister, you could take out and plug the lines, and check if vent is leaking. Vent is normally open, so you need to apply 12 or 9V to close it.
Cheaper than smoke machine but much more labor intense.
If we assume all rubber hoses, lines, connectors, etc. as fine and gas cap is not a problem, the only "mechanical" part that's left is the vent valve. For info about that take a look at https://acurazine.com/forums/3g-tl-p...-p2422-990658/
08-27-2009, 05:22 PM
