Troubleshoot codes I have a problem with codes p0442, p0455, p0456. I looked up p0456 and somebody said that they replaced the stock champion plugs to different plugs. He said that it helped. What can i do to fix the problem.

Po442 is evap system leak
check intake and all vacuum hoses for leaks
check evap canister and purge valve
Po445 is evap canister purge valve short circuit
check wiring and connection

What code ? P0442 or P0456 or p0455
DTC EVAP P0442 P0455 P0456
EVAP Leaks P0442 and P0455

Wells EVAP Training with Sgt Tech P0440 P0441 P0442 etc

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.

all codes are emsions codes you can look them up on this site and they also give probably fixes http://www.obd-codes.com/p0420

The Dodge P1494 engine light code means Leak Detection Pump Switch or Mechanical Fault. A proper diagnosis must be done, you can't simply replace the LDP and expect that to fix the problem. It shouldn't hurt anything to keep driving it for a while until you can get it fixed.
There is a technical service bulletin that applies to your vehicle and it mentions that code specifically. I'm including it here for your information: TSB-18-01-00
SUBJECT: Misdiagnosed Leak Detection Pump Systems With DTC P1494, P0442, P0455, OR P0456.
MODELS: 1997 - 2000 (LH) Concorde/Intrepid/LHS/300M/Vision and others
DISCUSSION:
During evaporative system diagnosis, Leak Detection Pumps have mistakenly been replaced. A thorough inspection for pinched, kinked, or disconnected supply vacuum lines (as currently listed in the Powertrain Diagnostic Procedures) is a critical step in diagnosing DTC P1494 (LDP SW OR MECHANICAL FAULT). Additionally, the other evaporative leak faults (DTC P0442 - SMALL LEAK, P0455 - LARGE LEAK, and P0456 - VERY SMALL LEAK) should have the supply vacuum lines examined for pinches or kinks prior to any LDP component replacement. The supply vacuum lines should be checked from the engine compartment all the way to the fuel tank, including the LDP and purge system.

NOTE: VERIFY ALL RELATED SUPPLY VACUUM LINE ROUTINGS FOR PINCHES, KINKS, OR DISCONNECTION'S BEFORE REPLACING LDP SYSTEM COMPONENTS.

Hope helps (remember rated and comment this).

LEAK DETECTION PUMP SYSTEMS (P1494, P0442, P0455, P0456),

http://www.obd-codes.com/

P0700: EATX Controller DTC present
P1684: Battery was desconnected
P0442: EVAP leak monitor medium (.040). Leak detected.
P0455: EVAP leak monitor large. Leak detected.
P0456: EVAP leak monitor small (.020). Leak detected.

I suggest check the lines and flow it down to the ldp (leak detection pump) that is just behind the steering gear under the van It has a wire connector and 2 large EVAP hoses. look for any split or crack then follow the lines back to the tank. Even a small crack is a leak.

Hope helped with this. Remember rated this help. Good luck.

hello po442 ,po455,po456 is leak detected possible, check the gas cap , basicaly you have a leak that is larger than 0.020' and smaller than 0.040' in the gas evaporative system use your nose to find this one thanks

P0442, P0455 AND P0456 are all evaporative leak monitor test failures (small, medium and large leaks). These codes appear anytime the integrity of the air space above the fuel or the lines to/from the vapor canister or purge valve. If there is no damage to the canister, check the lines that run under the van from the fuel tank and canister to the purge valve (under the hood). Also, check to make sure that the hoses are not split or disconnected where they connect to the purge valve. The P1684 is abit more confusing. This is not a valid DTC for your vehicle. It's possible the scanner the shop you went to is an OTC scanner that is reporting a false code. It's also possible they wrote it down incorrectly. The closest thing that makes any sense is a P1486 which would indicate a pinched hose in the same monitor system as the other 3 codes. Best of luck!