Own a 1999 Honda Accord with 169,000 miles. My check engine light came on?

I went for a smog check and everything passed except for the OBD part because the system wasn't ready to read or some crap like that.
Mechanic told me to drive it for couple of days and it'll be fixed and to see him again and it'll pass smog. So I've been driving it for two weeks now.

Well recently my Check Engine light came on and I'm not sure if it's because of the OBD or cause my engine really needs to be checked.

Thing is I only have $100 left and I don't know how much it cost to check the engine. I get paid next week. Anybody know prices?

Due to failed smog I only have about three weeks before temporary driving permit expires (not a permit like before a license, but a permit for driving car with failed smog).

Sidenote: I live in San Jose, CA in case you're wondering about location.

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