There is one thing that all of these have in common---THE BATTERY
If the battery has an internal short it can still have proper voltage and everything can work. An electronic digital battery tester can find that problem, also the alternator could have a bad diode sending A/C voltage thru the system causing havoc as well, It could very well be the ECM as well. They could also be individual problems as well, the O/D light flashing is usually cause by to much line pressure in the trans, there is a solenoid in the trans called the EPC--Electronic Pressure Control, that will cause that problem. The ABS light and the Brake light on at the same time is usually low brake fluid which means it is time for a brake job- your pads are worn out, the A/C could many different problems-you could have a freon leak therefore you are low on freon, you could have a bad blend door motor which would allow the heater to heater air to blend with the A/C air giving you warm air and as the speedometer goes, wiring, sensor, speedo....a professional needs to look at it to let you know--good luck
