klskLS400

Found the reason for my issue. Thanks, guys, for all the ideas.

Scenario:
-Driving along, 3rd brake goes bad
-Start having starting issues
-Thought I had a bad battery -> So I bought a new battery

Then:
-New battery went bad (wtf?). Checked battery voltage at idle (14.4, sweet!). Checked battery voltage when car was off (9.6V, not good). Wanted to buy a new battery and alternator, now! Wait....the idle voltage was 14.4 that can't be it...

Finally:
-Checked parasitic drains by pulling one fuse at a time and measured with my DVOM set to mA. Draw was 330mA with all fuses in. (that's BIG)
-Found MPX-B fuse (10A), when removed, dropped parasitic draw to 2mA (that's more like it)
-Googled the fuse. Turns out to be related to body ecu's etc. (Hmm, wonder if this has anything to do with those blown taillamps)
-Replaced burnt bulbs (they were charred)
-Checked parasitic draw with MPX-B fuse put back in (have to wait a few seconds while ECU draws settle down). New parasitic draw - 0mA (hooray!)
-Started the car. Starting improved alot! Radio working better! (sensitive to battery voltage).
-Let it idle to charge the battery
-Shut down and start again -> battery charged! sweet.

Moral of the story - the blown taillamp bulbs may have been keeping an ECU awake at night or otherwise some other short to ground. Replacing the bulbs solved my starting problems and battery drain.

Do your maintenance! Esp on a sweet LS400

INTIMAZY

iTrader: (5)

Awesome! Need to troubleshoot mine too. Had an issue with slow drain ever since I bought it.