I am really struggling to solve this problem. I have a .5amp parasitic draw on my battery through the dome light circuit and the ECU-B circuit. Once those 2 fuses are removed the drain drops to 0.012amps as measured properly. I have already tested a replacement body control module, that did not solve the problem. Things I have checked/replaced.
1. Brand new battery. No effect, has tested good by all possible means to test a battery.
2. Body ECU (Body Control Module) has been swapped with a known good module, no change in symptoms.
3. All wiring and grounds for affected circuit checked. Resistance well below acceptable levels for wire gauge and wire length.
4. New replacement drivers side lock/window controller, Seems to have made things worse.
Symptoms;
1. Parasitic battery drain 0.5-0.6 amps.
2. Door locks not responding to external key fob either through buttons, or turning the lock manually.
3. Auto down and auto up window functions from drivers door not functioning. Windows will not roll down when key is turned and held. Windows will also not roll up with key turned and held.
4. Alarm cannot be set by turning key in lock as the locks do not respond.
Vehicle is completely stock. No modifications to any system. Vehicle has 167K and runs very well besides poor gas mileage.
Any help with this or suggestions on how to repair is greatly appreciated.

 

I love puzzles like this, one question I had as every issue seems -- I didn't look at a wiring diag -- but they seem to run through the new controller and I didn't catch why you swapped the controller to begin with.

 

I would focus on cause and not the effects.

The door lock seems to be the cause. The current drain is based on vehicle recognizing the state it is in. Lots of stuff gets primed/ready once the door is unlocked.

Salim

 

I had a similar issue a few years back with a parasitic drain and doors not locking/unlocking with the fob.

After a couple of batteries and lots of hand wringing, it turned out that the trunk carpet had shifted and slightly kept the hatch from closing entirely - it latched but apparently not all the way.

In a week or so of not driving, the battery was dead.

Check your of doors and switches. If the doors don't lock then the car thinks one of the doors is open.

 

2001 RX300 Also. Recent parasitic battery draw killing battery overnight. Watched YouTube videos that described how to identify which circuit was not turning off at key shutdown. Entailed connecting Ammeter to negative- (black) battery post and then pulling each fuse to see which circuit is causing the draw. Too complicated for me. My mechanic has an electrical specialist come in 1X/week. Measured .22A battery draw when ignition turned off. Isolated power circuits to Dome and ECU-B circuits. Traced both circuits to Instrument cluster. Removed two Instrument clusters and tested for no battery draw. He downloaded wiring diagram from internet and then rewired Instrument cluster.to eliminate constant battery source from powering instrument cluster while vehicle is off. Reinstalled instrument cluster without computer memory, which was not required for vehicle operation. Checked operation OK and battery draw was gone. Conclusion: Too complicated for DIY owners. Cost $350US. Well worth for 200K mileage, well running Lexus SUV otherwise.