Check engine light . shows code p0456 evap small leak detected. how do i check charcoal canister hoses? or is that a job for a qualified mechanic? i checked gas cap seal and seems ok. any other suggestions ?

A P0456 is an EVAP small leak detected. Leaks can be notoriously difficult to find without the proper test equipment. It's like plumbing in your home with pipes, tubes, and connections running virtually the length of the car.

The procedure for diagnosis involves a "smoke machine" that shows EVAP system flow volume (identifies leak in progress) and fills the system with smoke to pinpoint the source(s) of leak(s).

The P0496 was a EVAP large leak.

Suggest you ask the shop what equipment they used to diagnose YOUR Sonata leak and if they didn't use a smoke machine for diagnosis, I would take it to a shop that does.

Finding ALL the leaks can be done without a smoke machine but it's your money they're guessing with.

Tom, Yes, you should check all evap hoses for cracks and leaks.
Common Problems That Trigger the P0442 Code

• Defective or damaged fuel cap
• Distorted or damaged Fuel Tank Filler Neck
• Small tear or puncture in the Evaporative system hose(s) and/or Carbon Canister
• Defective Fuel Tank Sending Unit gasket or seal
• Small split in a seam of the Carbon Canister
• Defective Evaporative Vent Valve and/or Evaporative Purge Valve
• Defective or damaged Fuel Tank
• Defective Fuel Tank Pressure Sensor
• Defective Leak Detection Pump
• Slightly loose and/or worn clamps or hardened O-rings anywhere in the EVAP system Check the attached links,
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How Diagnose Check Engine Light Code P0456 Small EVAP Emission Leak

Volvo S70 Evap Small Leak Common Problem P0442 Charcoal Canister Hose Fix

This elaborates more on the code.
P0456 - Evaporative Emission System Leak Detected (Very Small Leak)
Description:
The powertrain control module (PCM) monitors the complete evaporative emission (EVAP) control system for the presence of a very small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 0.508 mm (0.020 inch) is detected by the EVAP running loss monitor test.
Possible Causes:
• Very small holes or cuts in the fuel vapor hoses/tubes
• Loose fuel vapor hose/tube connections to the EVAP system components
• EVAP system component seals leaking. See the Possible Causes for DTC P0442
Diagnostic Aids:
Check for a missing fuel filler cap or the integrity of the cap.
Check for loose or damaged vapor hoses. Visually inspect the EVAP canister inlet port, CV solenoid filter, and canister vent hose assembly for contamination or debris.
Application Key On Engine Off Key On Engine Running Continuous

P0456 - Evaporative Emission System Leak Detected (Very Small Leak)
Description:
The powertrain control module (PCM) monitors the complete evaporative emission (EVAP)
control system for the presence of a very small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 0.508 mm (0.020 inch) is detected by
the EVAP running loss monitor test.
Possible Causes:
• Very small holes or cuts in the fuel vapor hoses/tubes
• Loose fuel vapor hose/tube connections to the EVAP system components
• EVAP system component seals leaking. See the Possible Causes for DTC P0442
Diagnostic Aids:
Check for a missing fuel filler cap or the integrity of the cap.
Check for loose or damaged vapor hoses. Visually inspect the EVAP canister inlet port, CV solenoid filter, and canister vent hose assembly for contamination or debris.
Application Key On Engine Off Key On Engine Running Continuous

Here's what comes up.click on link.Trouble Code: P0456

EVAP Small Leak (0.020") Detected

Possible Causes:


EVAP fuel tank or canister vapor hoses leaking or damaged.EVAP system component leaking, fuel cap loose or missing.Leak detection pump damaged or leaking.

P0456 is Evaporative Emissions System - Small leak detected.

More often than not it is a gas cap that is either not put on corrert or it has failed to hold the seal.
Less likely causes are:

• 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

P0442 - Evaporative Emission Control System Leak Detected (small leak)
This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Symptoms: You likely won't notice any drivability problems.

Causes: A code P0442 most likely means one or more of the following has happened:
A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
A small leak/hole in a fuel vapor hose/tube
Other small leak in EVAP system
Faulty vent o-ring seal

Possible Solutions: With a P0442, the most common repair is to:
Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
Otherwise, replace the gas cap, or
Inspect the EVAP system for cuts/holes in tubes/hoses



P0456 - 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.

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.


Test it; keep us updated and remember to rate this answer.

P0456 = "Evaporative emission (EVAP) control system leak detected (very small leak)."

Which code specifically? Do not assume you need a new solenoid. Our recommendation will depend on the specific code and some troubleshooting results. I usually recommend checking over all the EVAP vacuum lines and the gas cap too whenever there is a purge valve code. Check the vacuum lines at the cannister in the left rear bumper. I will paste info on the purge solenoid below.

P0440 Evaporative emission (EVAP) system - malfunction

Possible causes: Hose connection(s), intake leak, EVAP canister purge valve

P0441 Evaporative emission (EVAP) system - incorrect flow detected

Possible causes: Hose connection(s), intake leak, EVAP canister purge valve

P0442 Evaporative emission (EVAP) system - small leak detected

Possible causes: Hose connection(s), intake leak, EVAP canister, EVAP canister purge valve

P0443 Evaporative emission (EVAP) canister purge valve - circuit malfunction

Possible causes: Wiring, EVAP canister purge valve, ECM

P0444 Evaporative emission (EVAP) canister purge valve -open circuit

Possible causes: Wiring open circuit, EVAP canister purge valve, ECM

P0445 Evaporative emission (EVAP) canister purge valve -short circuit

Possible causes: Wiring short circuit, EVAP canister purge valve, ECM

P0450 Evaporative emission (EVAP) pressure sensor - circuit malfunction

Possible causes: Wiring, EVAP pressure sensor, ECM

P0455 Evaporative emission (EVAP) system - large leak detected

Possible causes: Hose connection(s), intake leak, EVAP canister, EVAP canister purge valve

P0456 Evaporative emission system - very small leak detected

Possible causes: Mechanical fault, hose connection(s), EVAP pressure "sensor

P0457 Evaporative emission system - leak detected (fuel cap loose/off)

Possible causes: Mechanical fault, hose connection(s), EVAP pressure sensor

P0458 Evaporative emission system, purge control valve -circuit low

Possible causes: Wiring short to earth, EVAP valve

P0459 Evaporative emission system, purge control valve -circuit high
Possible causes: Wiring short to positive, EVAP valve

Evaporative Emission Purge Solenoid

Description & Operation
The duty cycle EVAP canister purge solenoid (DCP) regulates the rate of vapor flow from the EVAP canister to the intake manifold. The Powertrain Control Module (PCM) operates the solenoid.
During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.
The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM cycles (energizes and de-energizes) the solenoid 5 or 10 times per second, depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time that the solenoid is energized. The PCM adjusts solenoid pulse width based on engine operating condition.
Removal & Installation
The duty cycle evaporative (EVAP) canister purge solenoid is located in the engine compartment near the brake master cylinder.

1. Disconnect electrical connector at solenoid.
2. Disconnect vacuum lines at solenoid.
3. Lift solenoid slot from mounting bracket for Removal & Installation.

To Install:

1. Position solenoid slot to mounting bracket.
2. Connect vacuum lines to solenoid. Be sure vacuum lines are firmly connected and not leaking or damaged. If leaking, a Diagnostic Trouble Code (DTC) may be set with certain emission packages.
3. Connect electrical connector to solenoid.
   

Purge solenoid location:


EVAP cannister location:

P0456: Evaporative Emission System Leak Detected (small leak)

Using a Multimeter, check the Evaporative Emission (EVAP) Canister Purge Regulator Valve N80 terminals 1 and 2 for resistance. You should get 22.0 to 30.0 Ohms. If not, replace the canister. If you do, you have other problems.