2000 TL - 2nd Tranny - 180,000 Miles. While driving, ABS, TCS, and SRS lights came on. WHen I stopped battery was dead. Swapped out battery and car ran great. Coming home the next night same thing happened. Only had 11.5 volts at battery with car on. Changed alternator. ABS and TCS lights coming on and off, dash lights surging, only twelve volts at battery while running with headlights, and heater on. ALso getting poor gas mileage. Not sure what to check next.

 

Check the voltage at the alternator. It kinda sounds as though that alt is bad.

 

stop by a parts store for a free system test
even a brand new battery needs to be driven on to fully charge-- to the cars specs!
a dieing batt may take the alt out with it- and the reverse situation

reset the ECU by pulling the CLOCK fuse on passenger end of dash for 1 minute-
thats the secret backup power to the ECU and clears codes- forces a self test of all systems and more
Using clock fuse instead of batt neg cable means you dont have to enter to radio security code or other resets

ck your batt cables-the ends are sandpaper or wire tool cleaned and rough?
connections to frame get removed, sanded and put back tight?
there are several ground wires for the car

some years require reset of throttle idle sensor and auto window operation

 

cking voltage with heavy load at idle isnt telling you all the truth-
what does it put out at 2000 rpm- normal cruise?

 

You didn't mention the battery light coming on, but maybe that was a given???

Was the replacement alternator used? Are you sure it is compatible? I believe there are differences between even 2nd gen years, and between regular and type-s.

 

even brand new or freshly rebuilt parts can fail
I always suspect the last thing done on the car!