Check engine Light (emission Control System)

check engine lights report on engine and transmission faults
if it is only in the rain I suspect that the wires and connections to the box or in the engine compartment are being affected by water getting into the couplings in the harness.

That's hard to say without a little more detailed information ! Was the check engine light on ? If so what codes ? There are a lot of reasons for not passing a emission test ! The engine management system is very complex an has several sensors that input voltage info to the engine computer, which in turn controls out put devices . injectors ,purge solenoid , shift solenoids , idle control etc.. No I could say with the information you supplied ! PA EMISSIONS WAIVER

Take it to autozone or another place like it and have them read the codes and tell us what they are.

My Audi Q7 has an V8 Fsi Engine and the check engine light is turned on ince years. But I cannot pass inspections, so year after year I am hvg those problems. Audi cannot find the problem! Better no more Audi!!!!

DTC P1457 - EVAP Emission Control System Leak Detected (Control Canister System)

It means your vehicle's computer has determined that a component or system in your emission control system is not working properly.
When the light comes on, one or more diagnostic trouble codes (DTC) are stored in the engine control module. These DTCs remain even if the light goes out. To address a Check Engine Light problem, the DTCs are retrieved and the appropriate troubleshooting information is followed in order to determine the problem.
Every vehicle manufactured in the U.S. has to first pass an Environmental Protection Agency (EPA) test called the Federal Test Procedure. This sets the acceptable limits of wear and/or failure for the emission control system-i.e., what conditions will ultimately cause a Check Engine Light to illuminate. These standards are closely regulated. If the emission control system is faulty and the vehicle is polluting the air, the Check Engine Light illuminates to alert the driver of this condition. (Note: A vehicle in this condition would fail an emissions inspection or smog check.)
Don't confuse the Check Engine Light with the maintenance or service light. These lights illuminate when a routine service is due. They are usually triggered by mileage, gallons of gasoline consumed, or some other type of vehicle-use measurement.

Abs light will not effect your emissions and will not fail your emission test either.

Check for water entry into vehicle, may be getting into engine control unit. Engine C/U located behind glove box on right hand drive vehicles so if water entry is the problem then the windscreen seal is the most likely point of entry.

Dear atomicboy488,

A lot of Rain=Possible Water in the Gas=Erratic Running!
This sounds like it may be as simple as cleaning the water or gunk out of the gas tank which is what I always do 1st because it's easy and inexpensive.
If your fuel is contaminated with gunk, grime, WATER and/or bottom junk like rust this will cause stalling AND ROUGH ACCELERATION!
Try spraying a can of starter fluid in the air intake and see if it runs! If it does, it's most likely bad fuel or clogged injectors so....
Fill the tank with High Test, Add some DRYGAS and a good fuel system cleaner or 2 or 3 and this should dissolve all the gunk and clean the injectors! Read & follow the cans' instruction carefully.
If this cures the problem never let your gas tank get below 1/4 and especially never run it to empty as this is when the gunk and/or water will enter the system!
Hope this helps!
Good Luck!
jackiaria
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You need a charcoal canister and vent control valve.

You also need the EGR solenoid valve (I think it the brown one).

Valve is located in the valley of the V, towards the transmission side of engine.

Do these 1st and reset light. You may have other issues but you have to start here.