2005 4runner V8 battery drain problem

[jimichu]

My 4runner has not been able to start recently, every time I have to jump start it, the battery is new, cost me 150bucks, and then I checked the battery drain by pulling out the fuses one by one and tested with a multimeter, it turns out the drain source is from the ECU/B and J/B 50A fuse, the ECU/B eats a 0.1A current, the J/B 50A eats a 0.2A current, after I pull both of them out, I get a 0.07A current, which seems to be the normal value, pulling the ECU/B out results in passenger airbag off signal and traction control signal, pulling the J/B out results in no electric window, that's what I found up to now, I think I really need some suggestions here. thx everyone

 

[BlackWorksInc]

70miliamps is still on the high side. How are you measuring your amperage draw? By hooking inline with the circuit? If so, that will lead to some slightly skewed results, the best way to measure small amperages like that is with a low amp current probe hooked to your DVOM, I would also be careful with hooking your DVOM into the circuit for current testing as you can blow the fuses if you forget to disconnect it and open a door or wake something up.

You sound like you've got the basic diagnostic path down right, having narrowed down the draw to those two circuits. The problem now becomes a matter of finding out what draws are acceptable and what aren't you're going to need to dig up the wiring diagrams and start testing and trying to figure out how many branches come off that fuse. For example the ECU/B fuse might have a few wires supplying current to various components in the ECU/B circuit and you'll need to test each branch and figure out what is drawing power and make the judgement call if its a problem.

I actually just updated the http://www.toyota-4runner.org/4th-gen-t4rs/132953-toolbox-how-use.html Sticky last week to include a section on testing for parasitic drains, you're pretty much on track but maybe it can help.

 

[jimichu]

thx for the quick reply, I tested the current by disconnecting the ground terminal of battery and connecting the multimeter into the circuit, I use a 10A range for it.

I can live with the ECU/B pulled out, but pulling the J/B out will let me not able to roll down all the windows, so I have to fix it,

the manual says J/B fuse "All components in “PWR OUTLET”, “D P/SEAT”, “P P/SEAT”, “POWER”, “TAIL” and “SECU/HORN” fuses", that seems a lot components to check!

I do have a Aftermarket Alarm Systems installed(I bought it as a used car), I havn't found a way to disconnect it though.

 

[BlackWorksInc]

Yeah, it is a lot of circuits to test, ideally if you had a low amp current probe you just clip onto the supply lines from that fuse and narrow which part of the circuit you need to look at before digging into the car further. For Example, I had a Hyundai Tuscon with a parasitic draw just the other week and I narrowed it down to one fuse that killed the draw when pulled. That one fuse supplied power to a dozen interior lights, instrument cluster, modules, HVAC, ect. I ended up locating the splice (which happened to be right at the fuse block) and used my probe on each branch wire and narrowed it down to the rear door interior light (weirdly enough the bulb was drawing current almost equal to it being on, but not actually lighting up, replacing it fixed the problem.)

The point being, the more you can narrow it down by doing the least amount of work is the key to efficient diagnostics. I would get the make and model of your aftermarket alarm system and then use that and the factory wiring diagram to see how it was installed, I have a feeling that the alarm is tapping into the circuits you've narrowed down to and be part of the problem.

 

[jimichu]

just before I call it a day, I opened the fuse box under the wheel, I saw 3 fuses hanging there on some strange circuits that seem to connect to the alarm system, then I guessed the factory fuses shouldn't just hang out there, so I pulled all of them out, guess what, I measure only 0.03A now, all I lost is just the remote key beep sound, the remote key still work, I then charged the battery for a while and after that I started several times with no problem, drove to dinner and back. I'm leaving the battery terminals connected tonight and see what I get tmr. THx for the help! saved my day

 

[jimichu]

and BTW, the ECU fuse was just fine, the current from that fuse last only a few seconds and then goes away, the problem is indeed the alarm( by now )

 

[BlackWorksInc]

I figured as much, 30miliamps is an acceptable parasitic draw. You'll have to get the diagram for the vehicle and the alarm and try and figure out where they messed up in the installation.