I posted trouble with dash lights going out a few days ago, as I search for an answer I hear about onboard diagnostics. What is this and how do I display. I have 1994 Eldorado, does it have this device. I know you can check oil, temp, volts, etc. Not sure how onoard diagnostics works. Do I have to take into dealer to get reading or can my husband find this information. Any help would be appreciated as car is getting worse.
Linda
Linda