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.
Just turn on ignition, press and hold "off" and "warm" buttons for ~3 sec. This enters diagnostic mode (its good to have paper and pen ready). Then computer shows diagnostic codes. what those codes mean - by Katshot