I have a 1999 Accord, F23a1 (VTEC 2.3, STD Tran).
My alternator went out so i replaced it. Well now that i have it back in, my Speedometer doesn't work, and when i have the parking brake on, the dash shows that all 4 doors/trunk are open. But when i release the brake, it corrects itself. Also, when I turn my headlights on, My tach turns off, just drops to zero, engine speed isn't affected (at least i can't hear anything), and random lights show up: SRS, ABS, etc.
Several CEL Codes!
-O2 Sensor
-O2 Sensor Heater
-Vehicle Speed Sensor (just replaced it though)
-Voltage Regulator/ECM

Any ideas?

 

Without having the vehicle here to check out I recomend you bite the bullet and pay a professional to take a look at it. After double checking your work, of course.