Small Vacumn leak

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

when check engine light comes on VSC is disabled. small leak is for evaporative system (to prevent fuel vapors from entering the atmosphere) small leak is A leak less than forty thousandths of an inch, it could possibly be a gas cap not fully tightened,leak in a vapor line,leaking fuel filler neck,gas tank leak,purge valve,vent valve just to name afew. clearing code will turn off both lights but if theres a leak lights will come back on.

erase code again , then disconnect battery for a few minutes, reconnect, see if code comes back. hopefully this resets computer. you don\'t have a reset button on steering wheel do you ? replace your fuel filter, if you haven\'t lately. maybe that will help.

check the vacumn pipes as this is a old vehicle and not a lot is that complicated compared to modern vehicles so this light is just turned on for no oil pressure or water level also a vacumn leak to the ignition advance unit,Yes no OBDII on a vehicle this age which means that most young mechanics wouldnt have a clue unless they plug something in and play bill gates ,if in doubt use a automotive multimeter and check the dwell ,voltages on the O2 sensors and so on then you should find the fault but check the vacumn pipe to ignition module first

P0401 indicates that the Exhaust Gas Recirculation Flow Insufficient Detected. This can be because EGR is faulty . As you have replaced this then the problem must be with the vacuum line . EGR valve vacuum line which can be broken or blocked. The vacumn ine must bbe checked for leaks or any blocks using an vacumn pump connected the line.

P0420 indicates that the down stream oxygen sensor reading is not steady and it is connected with the code P0401.

There may be a couple of items to look at here.... but the most common problem is a source of vacumn to the pneumatic operation of the heat/a/c vent doors....if vacumn is not distributed properly to the vents you command it is assumed that there is either no vacumn to the selector swith panel(broken vac. line,kinked vac. line, defective in dash a/c control panel) or under the hood a defective vac./heater control valve that is stuck,frozen, not allowing the vacumn to pass through it to supply the indash pneumatic controls and/or panel.
Most vacumn systems that i have ever came in contact with incorporate a vacumn supply tank(nothing more then a round plastic vac. resevoir) which is used in sequence with the a/c heater controls, its purpose is to keep an even vacumn supply to all command points continously while the vehicle is being driven, without this supply one will experience the a/c coming from various different non selected dash vents upon acceleration, this is a direct relation to the tank either being defective(leaking vacumn) or its supply hose(usually vey tiny rubber/plastic tubes) being pinched or broken not allowing the vacumn to the supply tank.
listen for vacumn leaks(hissing sound), look for the obvious...broken vacumn lines or hoses, also check for a defective one way vacumn valve on some pneumatic controlled door vent systems(these valves are inserted in a vacumn line one side being the ""in" port and the other side of it being the "out" flow port,typically if these dont work the vents will also devert your a/c or heat all different ways through your dash.
to check these valves, simply remove from the vacumn hose, and apply vacumn to one side,if vacumn flows through the valve, apply the same vacumn to the opposite side of the plastic valve, if vacumn flows through on the opposite side the valve is bad, it should only allow flow from one side not the other. These valves are small and are usually white or black plastic and look like the old vacumn dash pots used on the old carbureated engines only smaller with one small hose in and one small hose out.

P0442 OBD-II Trouble Code - Evaporative Emission Control System Leak Detected (small leak)

What does that mean?
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




Fig. EVAP vent solenoid (2) on 3.1L, 3.4L, 3.5L & 3.8L, showing the connector (1) and vapor line (2)




Fig. EVAP canister purge solenoid location on 3.1L & 3.4L




Fig. EVAP purge solenoid valve (3) location on 3.5L




Hope this help, good luck.

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.
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

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

The line runs from the purge canister to the fuel tank along the frame, what makes you think you have a leak? any kind of a vaccum leak would make the idle go up in rpm,s or the hvac with blower on would go from where ever you set it to defrost (default setting with no vaccum) if you are just getting a check engine light of small evap leak 99% of the time it the gas cap o-ring worn or cap not tight.

One will control the heater core valve, one will control the deflector door and one is problem vacumn in from intake manifold. If the vacumn motor that controls the valve or the door is leaking you would have this problem. Also if vehicle is low on anti-freeze you could have this problem, Hope this helps! The vacumn motors are easily checked by take a small piece of vacumn hose and intstall it on each one and applying suction by mouth, if they leak you will not be able to make them retract or they will leak down after you pull them in.