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I have a 2004 passat that sat for a couple years. New battery. When connected the Alarm goes off constantly and the Passat will not start (it does try). I read in my book that the ECM lost important memory when the battery died/got replace. Should I get ride of the car? Is there a reasonable fix or something I'm missing?

 

[FrescoGreen01.5]

I believe the ECM will lose throttle body adaptation, as well as readiness codes.

You can search for throttle body adaptation on the forum. There's a way to initiate it with the driver's door and hood.

As far as the alarm goes, you should be able to disarm it by unlocking the driver's door with the key.

 

[AndreasPassat]

Once the system is completely drained of electrical current, Throttle body adaptation (TBA) and other readiness codes will be lost.

If the car is worthy of anything, get a replacement / new battery, must have a minimum of 11.7 volts.
Getting yourself a version of VCDS here: Ross-Tech: Home will allow you to do a TBA and set all of the readiness codes.
Once the adaptation and readiness codes are set, you should be good to go.
Depending on location, letting a car sit for a few years might take a bit to get it started.

 

[Passatfan2]

I have a 2004 passat that sat for a couple years. New battery. When connected the Alarm goes off constantly and the Passat will not start (it does try). I read in my book that the ECM lost important memory when the battery died/got replace. Should I get ride of the car? Is there a reasonable fix or something I'm missing?

You need to get rid of the old fuel in the tank, after that long sitting that fuel is rotten. Put fresh high octane fuel in it so you can start it again..

 

[vwdoc1]

Ahh the fun of starting a car that has sat for quite a while will need these 4 things:
1. Fresh fuel, as others have said.
2. Compression in the cylinders
2. Air
3. Proper spark.

Which engine are you working with and the other questions I have is:
A. Why did it sit for a couple of years?
B. Was it YOUR car?
C. Did it run well when you did set it up?

Common non-start issues are Fuses, Fuel Pump Relay, ECM relay and Fuel pump. BTW any rodent issues with this car?

If you crank over the engine from inside the car you should be able to hear the fuel pump run/buzz for a couple of seconds after you release the key.
IF not check the relays or supply power and ground directly to the pump.
After trying to start the engine, pull 1 or 2 spark plugs to look both at their electrodes and down in the cylinder for any wetness or fuel. If it is wet, smell it for that fresh gas odor too!
Not wet then you can listen to the injectors while someone cranks over the engine. Use a screwdriver touching metal tip to one of the fuel injectors and plastic part to you ear.
If you can not hear the fuel injectors click, you could pull the Injector rail out and carefully lay them on a towel and crank the engine over very briefly to see in any fuel comes out of the injectors.
I have heard injectors click but not spray fuel properly but this is usually on a car that sat for many many years.

If you do get the fuel into the cylinders you have to check for compression and spark but I will wait for your fuel results.