I have a 2002 Ford Taurus, and an engine sign showed up. However, I pulled out the code which is P0442. what is the problem, how much would that cost me and when do I need to fix it, can I wait for the next week, or its something that needs to take care of ASAP. thanks,

Check for leaks,replaced fuel cap,smell gas?

Evap System--small leak

Google it & read about it

P0442 FORD - Evaporative Emission System Leak Detected Small Leak

Possible causes- Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking
P0136 - O2 Sensor Circuit Malfunction Bank 1 Sensor 2
Possible causes- Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
- Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
- Faulty Rear Heated Oxygen Sensor Bank 1
- Inappropriate fuel pressure
- Faulty fuel injectors
- Intake air leaks may be faulty
- Exhaust gas leaks

P0141 FORD - O2 Heater Circuit Bank 1 Sensor 2

Possible causes- Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit fuse
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit open shorted to ground
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit poor electrical connection
- Faulty Engine Control Module (ECM)

The information you are asking for varies depending on how the vehicle is equipped ie. ENGINE SIZE, AUTOMATIC or MANUAL TRANSMISSION, 2-WHEEL DRIVE, 4-WHEEL DRIVE, ALL-WHEEL DRIVE, etc.
With that said, it also deserves mention that there is a Technical Service Bulletin published by Ford Motor Company that applies to the model year and model that you have listed that involves Diagnostic Test Code (DTC) P0456.

Please note that this bulletin emphasizes the requirement of special equipment to properly diagnose and repair the DTC's listed in the bulletin. Below is a brief (partial) description of the bulletin:

Article No.
03-20-3
10/13/03
DRIVEABILITY - MALFUNCTION INDICAOR LAMP
(MIL) ILLUMINATED WITH DTC'S P0442, P0455,
P0456, P0457, P1442 OR CHECK FUEL CAP LAMP
ILLUMINATED WITH DTC P0457
FORD: 1997-2000 CONTOUR 1997-2002 ESCORT 1997-2003 CROWN VICTORIA, MUSTANG, TAURUS 1998-2003 ESCORT ZX2 2000-2003 FOCUS 2002-2003 THUNDERBIRD1997 F-250 HD
1997-1999 F-250 LD
1997-2003 E SERIES, EXPEDITION, EXPLORER, F-150, RANGER, WINDSTAR
1999-2003 F SUPER DUTY
2000-2003 EXCURSION
2001-2003 ESCAPE, EXPLORER SPORT TRAC, EXPLORER SPORT
LINCOLN:
1997-1998 MARK VIII
1997-2002 CONTINENTAL
1997-2003 TOWN CAR
2000-2003 LS
1998-2003 NAVIGATOR
2002-2003 BLACKWOOD
MERCURY:
1997-1999 TRACER
1997-2000 MYSTIQUE
1997-2003 GRAND MARQUIS, SABLE
1999-2002 COUGAR
1997-2003 MOUNTAINEER
This article supersedes TSB 03-9-8 to update the vehicle lines and Service Procedures.
ISSUE
Some vehicles may exhibit a Malfunction Indicator Lamp (MIL) illuminated with Diagnostic Trouble Codes (DTCs) P0442, P0455, P0456, P0457 or P1442 or a "Check Fuel Cap" Lamp illuminated with DTC P0457 for the Evaporative Emission System. This may be caused by loose or leaking hoses, loose or broken fuel cap, a leak at the top of the fuel filler pipe neck, etc.
ACTION
Use the Rotunda Leak Detector Smoke Machine (Part 218-00001) or equivalent, to locate and repair leaks in the Evaporative Emission System.

small EVAP leak

you'll need a smoke machine, scan tool and lots of time

real bear to find but start with the obvious under the vehicle lines that look like they may have suffered damage from rocks etc.

That code is for the Evaporative Emissions. It could be a bad Evaporative Emissions Canister Valve or just a bad vacuum line or my granddaughter's 1997 Ford Escort had that code and her gas cap was NOT on. Now when you figure out what one it is disconnect the battery for 10 minutes to reset the computer.

just because the light is back on, doent mean its the same thing. thats a lot of money spent on just those problems. (WAY TOO MUCH) Take it back and have them ck it again, or find a shop that knows what they are doing.

check your fuel regulator, pull the vacuum line off and see if its leaking fuel by the diaphram inside...
if you need more info just comment and we can trouble shoot this with you

Sometimes the parts store will help you with their computer pictures.Aslo the dealer will gladly print one for you,go to the parts department,smile and ask for one.

The only way to stop this is to stop the leak.
How the system works is the EVAP monitor which is a program designed to run at a certain time by the computer actually pulls a vacuum on the fuel tank by closing the canister vent solenoid and applying vacuum thru the canister purge valve and then monitors the fuel tank pressure sensor to see if it holds the vacuum. If it detects a gross leak it will set a code P0455 and if it detects a small leak it sets a code P0442.