What happens if i drive with code p0456 - 2005 Toyota Corolla

B1342 is not an engine code. P0456 is. Follow the link for more info. P0456 Evaporative Emissions System Small leak detected

B1342 is a manufacturer specific code so need to know make and model and year.

clearing the code doesnt fix the problem if its a problem with a component most clear this code because of gas cap either gone bad and or not on tight enough but the code is for a small leak and that can be any line in the evap system including the canister--damage or line seals can cause this problem the following can assist you with your problem
P0456 Evaporative Emissions System Small leak detected

I think I would clear the codes and see how many come back.
Code 456 is a small leak in the EVAP system that vents the gas tank. Sometimes the cause is leaving the gas cap off or loose.
Code 301 and 304 are loss of power on cylinders 1 and 4, and code 174 is fuel system too lean on bank two which is the side with cylinder 2. That code may be the key to the actual problem.
If the ignition system is in good condition and the plugs have been replaced, it may be a fuel problem.

Drive over to your local Ford dealer parts department; they can verify the part number your looking for- and they can also print out the schematic where it sits on the engine.

P0456 DODGE - EVAP System Small Leak
As you see form the list there is not a single problem that causes this code to set.
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

Read more: http://engine-codes.com/p0456_dodge.html#ixzz1xQr2MVRf

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.

http://www.obd-codes.com/p0456

This is usually caused by a gas cap that was not put on properly after a fill up. If this is the case then simply tighten the gas cap and the check engine light should go out in a few days with regular driving or reset with a code reader. You may have to replace the gas cap if the code remains. be sure to get the correct cap.

Check the link above for further tests.

p0456--emission control system leak(verysmall) leak, check all hoses to emission controls, cylinder 3 missfire detected. could be plugs, wires, or coil.this is code p0303,

Below are the possible causes for your engine light and error code:

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
  

The fuel cap is probably the most common cause of this problem. It's considered part of the emission system and if faulty or not place on the filler tube correctly, it will throw an error. Best of luck with your engine light issue. Take care!
Greg

P0456 = EVAP Emissions Control System Leak Very Small

Is the gas cap on tight or is the seal damaged? If it needs replacement, get it from the dealer.