This is a real head scratcher...tried lots of troubleshooting including taking to dealer for 2 weeks. Battery on 2002 4Runner goes dead after about 4 days of not driving. Replaced battery. Measured current drain in-line battery terminal...about 20-40 mA. Car runs great and no problems or warning lights. Tried several times to catch the issue by keeping multimeter in-line and check current drain periodically, but can't catch it. Seems to be intermittent problem. Dealer tried same, could not figure it out. Previous owner put a brake controller on it for towing, I removed all connections to the battery thinking that was the issue, but still have battery going dead after about 4 days of not driving.

Some hints that may or may not be related:
-once on starting up car, lots of warning lights came on, accelerator hard to push, no power steering. Shut off and started up again, everything fine.
-once when charging battery, noticed humming sound in TRC MTR relay, and in throttle body. Removed TRC MTR relay, disconnected accelerator pedal position sensor, and sounds went away. Reconnected, sounds came back. Decided to disconnect and let battery charge overnight. Reconnected after battery fully charged, no sound, car starts and runs fine. Dealer also noticed this noise, and recommended I replace the throttle body. I said prove that is what causes battery to drain and I will, they could not prove anything.

Sorry for long post. I am somewhat experienced with cars and elex...EE background. Any ideas? I was thinking it could be the ECM since it doesn't seem like there should ever be a condition when the TRC MTR relay is operating with the ignition switch off, likewise anything on throttle body operating with ignition switch off.

I would give a real thorough look at the ignition switch by the sounds of it. Test for power out when there shouldnt be. Just my .02

Good idea. Anyone know where I can get wiring diagram for ignition switch? Anyone know what should get power when ignition switch off?

I can e-mail you all the wiring diagrams for a 2002 4Runner

Just grab the FSM, the diagrams are in there. It is readily available here and elsewhere. Chech the reference and tutorial sticky

thx, got the manual. about 300 pages of wiring diagrams!
Plan on looking at ignition switch first. May pull all fuses that provide power with ignition off and see if that prevents battery drain. Then replace one at a time. Problem is it takes about 4 days for battery to drain. This may take awhile!

I have experienced the same thing twice. The first time, it was the daytime running lights that were somehow draining the battery. I disconnected the connection on the driver's side (to the right of the battery) and this solved it. The 2nd time around, I had installed LED lights in the cabin. The center light had somehow loosened up and drained the battery. Hope this helps!