Does this vehicle have a fuel shut off valve or solenoid, and if so where is it located?

look by the fuel tank

If your car has been bumped or has gone thru a deep pot hole, the mechanical fuel shut off valve may have triggered. Since we don't know what kind of car you have we cannot instruct you to the location of this valve. You can do a search on " fuel shut off valve" for the year and model of your car and reset it yourself once you know its location

No you don't have to remove the pick up bed to get at it. It's on the left frame rail along side of fuel tank !
Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle . Disconnect the evaporative emission (EVAP) canister vent electrical connector, if equipped. Disengage the 2 vent valve pipe clips securing the pipe to the underbody.
Remove the clips from the underbody and discard.
Disconnect the vent valve pipe at the EVAP canister. Remove and retain the EVAP canister vent valve bracket mounting bolt. Remove the complete EVAP canister vent valve assembly with bracket attached and discard.
Notice: Refer to Fastener Notice in the Preface section.
Video on youtube !

It's located under the vehicle back behind the fuel tank , Installed in the canister ! Remove the EVAP canister vent solenoid valve from the canister !
Rotate the EVAP canister vent solenoid valve counterclockwise in order to release it from the locked position.
Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle . Disconnect the evaporative emission (EVAP) canister harness electrical connector (2) from the EVAP vent solenoid valve. Clean away any debris that may be present around the EVAP canister vent solenoid valve.
Remove the EVAP canister bolt. Lower the EVAP canister.

Hi there:
DTC P0496 - EVAP (evaporative emission) Flow During A Non-Purge Condition


The P0496 DTC code is a generic code which applies to all vehicle makes. A quick search on the 'net shows that this code seems to be more common with GM (Chevy, Pontiac, etc.) vehicles. In Acura, Honda, Hyundai, Kia, and Mazda vehicles, this code is described "EVAP system high purge flow" which is the same thing.

This DTC checks for undesired intake vacuum flow to the EVAP system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve OFF and the EVAP canister vent solenoid valve ON. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system

If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this code is set and the MIL (malfunction indicator lamp) is illuminated.

Symptoms of a P0496 DTC will include MIL illumination, and most likely no other noticeable symptoms. Some may experience a hard start / crank condition. In some cases the engine may run rich which may not detected, but can cause damage long-term (think: catalytic converter damage).

Potential causes of a P0496 EVAP code include:

• Faulty purge or vent solenod/valve
• Plugged EVAP canister
• Failed EVAP / fuel pressure sensor
• Poor electrical connection
• Short electrical circuit condition
(Hyundai, Isuzu)
• Faulty canister purge valve
• Blocked vapor canister
• Faulty vent solenoid
• Leaking EVAP system hose (Hyundai)
• Faulty purge flow sensor (Kia, Mazda)

Possible Solutions

The most common fix for this DTC is to replace the purge solenoid valve. However, be sure to do a proper diagnosis before replacing parts!

Ideally you would use an advanced scan tool, with the ignition on and engine off, you seal the EVAP system using the Seal/Purge function. Then, watch the fuel tank pressure sensor reading when you turn the purge off. If the pressure value is higher than the normal range set by the manufacturer, replace the EVAP canister purge solenoid valve. Refer to a model-specific repair guide for the proper specification.

If you don't have access to the scan tool, you could always disconnect the vacuum line at the purge valve going back to the charcoal canister. Unplug the electrical connector on the purge valve, start the engine, then put your finger on the valve where you disconnected the line. If you can feel vacuum there, the purge solenoid valve is faulty and needs to be replaced. Alternately, you could simply remove the purge solenoid valve and blow into it. It is normally closed, so if air goes through then you need to replace it.

If the purge valve checks out good, either the problem with the valve is intermittent or there is a problem with the fuel tank pressure sensor. To test the fuel tank pressure sensor you will need to have a high end scan tool to monitor the tank pressure with the gas cap removed. If the sensor shows vacuum with the gas cap removed, there is a problem with the fuel tank pressure sensor.

Here is a picture of one purge solenoid valve. Yours may look similar or different, consult a factory service guide or your local vehicle dealership for more details.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

SOUND LIKE YOUR EVAPORATIVE EMISSION CONTROL NOT WORKING.SCAN VECHICLE FOR FOR FAULTY FUEL TANK PRESSURE SENSOR MALFUNCTION.AND THE CANISTER PURGE SOLENOID VALVE OR CANISTER VENT SOLENOID NOT WORKING.CAUSING EXCESSIVE FUEL PRESSURE AND FUMES BUILD UP IN FUEL TANK.CHECK CANISTER IT COULD BE GAS SOAKED NEED REPLACING OR VACUUM LINES GOING TO CANISTER PURGE SOLENOID OR VENT SOLENOID COULD BE BROKEN.PURGE VALVE LOCATED ON THE LEFT SIDE OF THE ENGINE ON A BRACKET AND VENT SOLENOID LOCATED ON A BRACKET NEXT TO FUEL TANK.CHECK BOTH MAKE SURE VACUUM LINES NOT BROKE OR DISCONNECTED.MAKE THE ELECTRICAL CONNECTOR INTACT ALSO.FUEL PRESSURE SENSOR ON TOP OF TANK ON THE FUEL PUMP MODULES.ALL YOU CAN DO IS REMOVE CANISTER SEE IF FULL OF GAS REPLACE IT.AND CHECK FOR BROKE AND DISCONNECTED VACUUM LINES.THE DEALERSHIP HAS TO HOOK UP DIAGNOSTIC EQUIPMENT CHECK IT OUT.BE CHEAPER BECAUSE ALL THEM EVAP PARTS NOT CHEAP THAT WHY LET DEALERSHIP SCAN IT SAVE MONEY IT WILL CUT THE COST.WARNING DONT KEEP DRIVING VECHICLE.GAS VAPORS PRESSURE BUILD UP ON HOT DAY FUELTANK WILL BLOW UP LIKE BALLON.PRESSURE KEEP BUILDING UP.

Here is a purge valve test from autozone.com. Is this what you needed, or what else?

COMPONENT TESTING
NOTE To relieve fuel tank pressure, the filler cap must be removed before disconnecting any fuel system component.
Canister Purge Solenoid

1. Locations vary depending on model and year. Typical locations include the firewall (left or right side) and the rear of the engine near the firewall.
2. With the ignition off, unplug the connector on the EVAP solenoid.
3. Turn ignition on, measure the voltage at the ignition switch output line, voltage should be 10.0v or more. If the voltage reading is not 10.0 volts or more, repair the circuit from the ignition switch to EVAP solenoid.
4. Disconnect the negative battery cable.
5. Disconnect the PCM harness from the PCM.
6. Check the resistance of the EVAP solenoid control circuit between the PCM harness connector and the EVAP solenoid connector. Resistance should be less than 5.0 ohms; if not, repair the opening in the circuit.
7. Connect the negative battery cable.

Fig. Purge solenoid mounted on V-8 engine

Fig. Purge solenoid installation on 2.5L engine-equipped vehicles

Fig. EVAP solenoid circuits and schematic

Fig. EVAP solenoid electrical connector

Code po449 is for bad  solenoid vent valve.After replacing the valve  check for the   12 volts at the "pink" wire.
This error relates too 

The PCM has determined that a malfunction exists in the electrical circuit for the vent valve/solenoid in the evaporative emission control system.

Definition:
EVAP (Evaporative Emission System) purge/vent solenoid circuit condition

Explanation:
The solenoids and system wiring are monitored for opens or shorts

Probable Causes
1- Purge or vent solenoids defective.
2- Check connector and wiring.
3- Fuel saturated vapor canister.
4- Failed EVAP vent solenoid.

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The cost of the vent solenoid valve is near to 30 bucks. And the valve is located near the gas tank.

Thanks. you can rate this solution and show your appreciation.

why do you want to replace it? As air is exhausted through it, it dires it out for the next use. it's part of compressor assembly.

1996 cont'l The air suspension system includes the following major components:

• Air compressor to supply air to the air springs (part of front spring and shock and rear spring and shock absorber assemblies
• Front spring and shock (3C098) and rear spring and shock absorber (5A965) at each corner of the vehicle
• Four linear air suspension height sensors (5359): two rear and two front height sensors to maintain the vehicle at the proper ride height; only LH rear height sensor is used for air suspension.
• Dual-mode front spring and shock and rear shock absorber assemblies with internal actuator.

All system functions are controlled by vehicle dynamics control module (5A919). This control module receives inputs from several different sources. These inputs include:

• vehicle speed via multiplex communication network
• ignition switch position
• door position via multiplex communication network
• height sensor position
• air suspension service switch
• engine rpm via multiplex communication network
• ride and steering personality settings via multiplex communications network

Communications monitor system operation and allow diagnosis of any concerns that may develop in the system. System monitoring for the driver's use is provided through the instrument panel mounted message center indicator (10D898).

• Diagnosis communication for the service technician is provided through the data link connector (14489) (DLC) under the instrument panel and Rotunda New Generation Star (NGS) Tester 007-00500 or equivalent.

The message center indicator will display AIR LEVELING DISABLED or CHECK RIDE CONTROL if the suspension system is not turned on or the vehicle dynamics control module detects a concern. If air leveling system disabled is displayed, check that air suspension service switch is in the ON position.
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Solenoid Valve Vent The vent solenoid valve operates as follows:

• The vent solenoid valve allows air to escape from the system during venting corrections.
• The valve is located in the air compressor cylinder head and shares a common electrical connector with the motor.
• The valve is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
• Air leakage past the valve tip is prevented by an O-ring seal.
• The vent solenoid valve opens when a corner of the vehicle is high and the vehicle dynamics control module (5A919) determines lowering is required.
• When the vent solenoid valve is opened, it provides an escape route for pressurized air.
• However, the vehicle will not lower unless the air spring solenoid valves (5311) are also opened to allow air to leave the springs.
• Lowering the vehicle corners requires the vehicle dynamics control module to open two solenoid valves, the vent and one air spring solenoid.
• Air is exhausted from the spring and vents through the compressor air drier (5346).

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Section 04-05: Suspension, Computer Controlled 1996 Continental Workshop Manual
REMOVAL AND INSTALLATION Air Compressor and Drier Assembly Removal

1. Turn air suspension service switch OFF.
   

1. Disconnect electrical connector located on the air compressor.
   

1. Disconnect two air lines from compressor air drier.
   

1. Remove three fasteners retaining air compressor and drier assembly to radiator support, frame rail and fender apron.
   

Ramon
P0420 relates to the catalytic converter. The computer sees little or no improvement in the exhaust before and after going through the converter. Either your oxygen sensors need replacement (3 total) or you need a new catalytic converter.
What is the mileage on the vehicle? Does it run well? Oxygen sensors generally start to fail after 70,000 miles. Catalytic converters usually fail because the engine is runnig rich and the owner ignores that fault for months. This causes the catalytic converter to overheat and fail.

P1456 relates to the evaporative emission system. This system holds the gas fumes in the system so they are not vented to the atmosphere. The most common cause of this code being set is failing to properly tighten the gas cap after refueling. Take the cap off and clean the sealing O-ring. Put it back on and tighten till it clicks 3 times. Make sure you have the correct gray colored gas cap. Clear the code and see if it resets within a few days. If it does, try replacing the gas cap.
Charlie