Question about Cars & Trucks
When you're doing a smoke test, any smoke that shows reveals the problem area if you are doing the test properly. If the smoke is showing near the top of the gas tank, you have a leak in the tubing or the vent valve is not closing (if it's in that area - you didn't provide make, year, model).
Posted on Dec 31, 2016
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Posted on Jan 02, 2017
Check the Fuel Pump Relay, it may be malfunctioning and need replaced. Also, in some vechicles, if the batter is disconnected and reconnected, the service engine light will come on from time to time, going off and on simultaneously. Have a diagnostics done to see if any codes show up. If no codes appear, then have them all cleared and drive for another 200 miles. Sometimes the computer will need to be cleared a couple times before the light will stay off. Make sure that all fuses and relays are good, and securey in place. Check all factory installed lights to make sure they are good, and securly in place as well.
Posted on Mar 31, 2009
make sure you get a cap from the dealer. I had similar issue.... bought cap from autozone...still threw the code....thought must be something else.
ended up replacing all the vacuum lines ... still threw a code
desperate, bought new cap from dealer.... problem solved!
Posted on Aug 25, 2009
This is a leak in the evap system that monitors and controls the pressure in the fuel tank. Make sure your gas cap is tight. There may be a cracked hose. There is a long line that goes from the gas tank to the evap cannister, which is usually in the engine compartment. Check the rubber hoses that connect this line to the gas tank and to the evap cannister. Also check the other hose that goes from the evap cannister to the engine intake manifold. If the hoses seem old and stiff, replace them--the cost of hose is small. Let us know if you need more help or have more questions.
Posted on Sep 14, 2010
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Info found at: http://www.obd-codes.com/p0456
Maybe try cleaning, tightening, or replacing the gas cap first?
P0456 Article by Dale Toalston ASE Certified Technician
Evaporative Emissions System - Small leak detected
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 (FTP) sensor. When the sensor indicates a small leak in the EVAP system, this code is set.
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.
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:
- 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
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.
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