Cadillac: 1999 Sedan Deville, heater blower, wire connections

Question
Heater blower motor won't work. Tried removing and checking fuses with no luck. Here's the kicker, now the car won't start. It turns over but won't start. Tried disconnecting battery already. Help please!

Answer
The first thing you have to determine is what is it you are NOT getting:

Fuel pressure to the engine or spark to the spark plugs.

Make sure that you did not disturb any wire connections when you replaced the battery.

Check the computers for codes.

1. Ignition ON. Engine OFF.

2. Simultaneously push and hold the OFF and WARMER buttons and the codes will start to display. Codes with the letter C are CURRENT codes and codes with the letter H are history codes.