Electrical Problem?

[87300SDLTurbo]

I posted earlier about a problem in which my warning indicators would come on (all of them) once the key is removed from the ignition. I was told that the alternator could be bad...I had an electrical shop do a test on the alternator with some sort of scanning tool and the alternator performed correctly.

I did a search on the topic and found an instance where someone had a similar problem and was told the ground strap to the engine was the problem. I pulled the skid plate and looked, the ground strap is right where it is supposed to be.

I am really confused. The problem also includes my glow plugs not working any more. There is also a small cylinder behind the passenger side headlight (it is directly under the air intake tube and has several vacuum lines attached to it) that seems to remain on unless the battery is unhooked.

If anybody has had a similar problem and could give me an idea as to how to repair this thing I would really appreciate it.

Thank you in adavance.