What would you do? (SES Question)

[KyleBucket]

So I have 26K on my '09 Z. 19K are my miles (bought used). She is my baby and I've never had issues with her. I've kept up with maintenance and such, however I got a voicemail to come in for my typical service (air filters, etc.) about a month or two ago? I figured I'd hold off until I got my oil changed again.

Today rolls around and my "service engine soon" light comes on. Never seen that before, so I'm new as to what to do. I just assumed "ah, alright. I'll go do the basic tuneup they called me for when they left that voicemail." I call Nissan to schedule and the woman says "oh no, we have to hook it up to the computer to figure out what it's asking. That's $130."

Now, I think that's total BS. Especially considering no one does anything but read a diagnostic, so I'm really avoiding spending that. I read AutoZone can diagnose the issue with a CEL. Called. Got a nice guy, but he said the SES is different and he can't guarantee anything. After describing the situation, he agrees with me. He thinks it's probably the basic maintenance and thinks maybe it's the oil. I said well, I have synthetic stock and the guy always "yells" at me when I come in at 4,500-5K and says push it to 7ish. I think that's a bit much, he agreed. He said "most lights would come on around 3,500ish." I check my alerts...I'm at 3,540 since my last oil change. So now I'm thinking that's probably it, along with the basic tuneup. The car has driven no different, everything seems fine. I mean, c'mon, I'm at 26K miles.

I don't want to neglect my car if there truly is an issue...but I really think it's what I described. What would you guys do? Do you agree? Maybe it's the battery (would that pull that light) because it does seem like she does start up as quick. It's nothing noticeable, but obviously when it's your car you notice little stuff like that.

Sorry for the lengthy post.