SWITCH TO D2 LIGHT/LOSS OF POWER

Is your check engine light on? If it is, Typically loss of power is a sign the catalytic converter is plugged and should be replaced

It's probably a bad turn signal switch, since the brake lights are wired in with the turn switch.
If you have a 3rd brake light, the high mounted one in the rear window, this light is separate from the brake lights that go through the turn switch. If your high mount brake light comes on, when brakes are pressed, then brake switch is good and probably a bad turn signal switch. Of course if you have a voltmeter or test light, you could test for power in and power out from the turn switch connector, to help you find the problem.

I can't imagine three brake lights all losing their grounds. You will need a volt meter to check (with the help of an assistant) to see if about 12 volts is available at the bulb socket's brake light socket (as measured to ground) when the brake pedal is depressed and held. Do the same for the other light and finally the third brake light. If there is a total loss of power at all the bulb sockets with the brake pedal depressed and held, check for about 12 volts coming to the brake pedal switch while not being depressed and that voltage comes out the other connection at the switch when the brake pedal is depressed. If power comes in on one wire but doesn't come out the other side when pressing the pedal this means the switch is bad. Replace it with a new one. Ne advised that SOME vehicles brake lights don't come on if the key is off, on most they work at all times even if the key is off.

How do you describe "loses power" ?
Does the engine stop, or what ?
If oil pressure drops below 5psi and the light comes on, you could lose power to the fuel pump.

if your fuse is good. and you have power at the brake light switch and when you hit the brakes you have power coming out the otherside of brake light switch/which would be the white wire/ check that the white wire is sending power up the turn signal switch. if theres power there and your turnsignals work? im afraid that your turnsignal switch is bad rare but it has been known to happen.

PROBLEM COULD BE IN THE MULTIFUNCTION SWITCH.

D4 is slipping and not engaging. This means you need a transmission. you're losing a gear

the shift to d2 light comes on when batt. voltage gets low enough that all of the sytems can not function properly. the noise is your bel slipping, your battery looses charge and shift to d2 light comes on to tell you to leave trans in drive 2 so it dose not have to use batt voltage to shift. replace your belt and tensioner if your alternator is ok.

Sounds like you got a deffective alternator. I would take it back and have them check it. It should put out between 14 and 15 volts, and if (and i'm saying if) that car is equipped with an external voltage regulator have that checked.

switch to 2nd gear