SEL on then off, is there a problem?

A few days ago, the SEL came on in my 04 trailblazer. My dad is adamant that since the car has 106k miles on it, the light means nothing at all. Today the light went out with no explanation or cause so I'm wondering if there is still a problem with the car or what it could have been. The manual says that the light being on is a problem with the ECS, is this a major issue? or can it be put off until later for checking out.

Also, the person we bought it from is a mechanic with his own shop. He says that if the light is out there is no way to read the error. Is this true?

Lastly, I know that on-star has recently started providing vehicle diagnostics on installed cars, is my car compatible with this? I am not subscribed to onstar in this vehicle, but if this works I might.

Thanks in advance...

First of all the lite indicates a problem no matter what you may feel when driving, second the only way to answer this is to scan it, there will be a pending or history code, your mechanic should know this!

Thanks for the reply. That's what I said to my dad, but he's set in his ways...

Anyways, what would you reccommend to scan the code. I have been trying to get my folks to buy one before, but they don't believe in the use of it. Now that I can go places on my own I'm at least getting one for my car.

Which one should I get and what are the differences?

Thanks

A " real" scanner that will give you live info can be expensive, upwards of 300 dollars and even at that price they are limited. I don't know what your diagnostic capabilites are but these scanners only provide info that then must be interpeted.

If the light is on or has been on there will be a code stored in the past/history or present section of the computer.

It should be ckecked out and fixed.
Running with a check engine light coming on can led to engine/transmission/and cat damage.
A good scanner can retrieve this information and many times a freeze frame of the problem will be stored in the computer.


If you are interested in a scanner shop around.
There is some PC based scanner programs that work good on a lap top.
Here is one of many out there.
www.Autoenginuity.com

Also some auto parts places will give you a fre scan.
But just get the code and check it out before you buy parts.

If it has 100K on it and never has been tuned up a good tune up is a place to start.