Parasitic drain - 2015 Toyota 4Runner

[RichardZ]

Hi - I could use some help with a parasitic draw that my 2015 4Runner suddenly developed. It drains the battery after a couple of days on non-use. This is my 1st time dealing with this issue.

When I disconnect the battery and connect my multimeter inline, the amps fluctuates between 0.475 and 0.575 (on the 10 amp setting).

I’ve narrowed it down to the ecu-b fuse. When I pull the ecu-b fuse the parasitic drain stops. No other fuse on the vehicle affects the parasitic drain.

What should be my next steps? Apparently, the ecu-b controls a lot of things on the vehicle, but I’m not sure the best way to start.

Thanks!

 

[Rand]

when you are testing is the door shut and the car left to sit for 30min to power everything down?

 

[RichardZ]

when you are testing is the door shut and the car left to sit for 30min to power everything down?

Yes

 

[bdc101]

What do the wiring diagrams say that the ECU-B fuse powers?

 

[RichardZ]

The car is stock. Nothing aftermarket.

 

[RichardZ]

What do the wiring diagrams say that the ECU-B fuse powers?

Seems like a lot >

 

[SC Maintenance]

My newer Toyota took almost an hour to go completely to sleep. Just to confirm - you left it sit and did not touch anything - not even open a door?

500mA is definitely too much. The ECU-B is the main ECU fuse I believe in Toyota world. If all your wiring is stock my guess is the next thing to check is all your Relays controlled directly through that circuit - might be one sticking on.

 

[RichardZ]

What do the wiring diagrams say that the ECU-B fuse powers?

Seems like a lot

My newer Toyota took almost an hour to go completely to sleep. Just to confirm - you left it sit and did not touch anything - not even open a door?

500mA is definitely too much. The ECU-B is the main ECU fuse I believe in Toyota world. If all your wiring is stock my guess is the next thing to check is all your Relays controlled directly through that circuit - might be one sticking on.

Thanks, yeah I left everything closed (including the hood latch) and read the amps over a few hours.

The battery has been replaced. I recently left it at an airport. I pulled the ecu-b fuse when parked, and it started after 3-weeks no problem.

I did pull each relay I had access to with no effect to the amp draw.

I would hate to pay a Toyota dealer to trouble shoot it.

 

[SC Maintenance]

I would hate to pay a Toyota dealer to trouble shoot it.

I would absolutely not do this. No disrespect, but most technicians get at most basic training on electrical troubleshooting. You might find someone that is good at it - at the dealer or Indy shop, but I wouldn't blindly hand this over.

Given you know how to use an Ohm meter you can probably find it yourself - even if you ultimately end up paying someone else to replace or fix whatever is broken.

500mA is too much, but still too low to power anything of significance. When you did the test - exactly what did you see and when. ie was it 500mA after like a minute and just stayed there, or did it start much higher and slowly drop down to 500mA. The when and how much can sometimes give some clues as to what system it might be. I suspect something is keeping your ECU from going to sleep at all. 500mA would account for a couple electronic modules.

 

[RichardZ]

It was after like a minute and just stayed there, but continuously fluctuated approx. 475-575.

Ps. I bought the 4Runner new. It has 162,000 miles. I’ve been learning about parasitic draw from som YouTube videos.

 

[SC Maintenance]

It was after like a minute and just stayed there, but continuously fluctuated approx. 475-575.

Ps. I bought the 4Runner new. It has 162,000 miles. I’ve been learning about parasitic draw from som YouTube videos.

My wild expletive guess - the 100mA fluctuation is something staying on or cycling, and that is keeping the ECU / BCU / security, etc on accounting for the other 475 mA.

If you can get it inside - get it cycling the 100 mA and see if you can hear a relay cycling. It will be hard to hear - will need to be almost otherwise silent.

 

[RichardZ]

My wild expletive guess - the 100mA fluctuation is something staying on or cycling, and that is keeping the ECU / BCU / security, etc on accounting for the other 475 mA.

If you can get it inside - get it cycling the 100 mA and see if you can hear a relay cycling. It will be hard to hear - will need to be almost otherwise silent.

Good idea. I actually have a stethoscope I can use. Won’t be until tomorrow. I’ll report back.

 

[bdc101]

Seems like a lot

Thanks, yeah I left everything closed (including the hood latch) and read the amps over a few hours.

The battery has been replaced. I recently left it at an airport. I pulled the ecu-b fuse when parked, and it started after 3-weeks no problem.

I did pull each relay I had access to with no effect to the amp draw.

I would hate to pay a Toyota dealer to trouble shoot it.

Can you provide a linky link to an electronic copy of the wiring diagrams? Or can you tell us what the exact model/trim is so we could look it up on ToyoDIY? (I still have a "secret" ToyoDIY account from the good old days before Toyota cease and desisted them.)

 

[K2K2]

Subbed.

 

[burbguy82]

Might be a case were the addition or a battery disconnect might be suitable. Save the battery, and anti theft.

 

[RichardZ]

Can you provide a linky link to an electronic copy of the wiring diagrams? Or can you tell us what the exact model/trim is so we could look it up on ToyoDIY? (I still have a "secret" ToyoDIY account from the good old days before Toyota cease and desisted them.)

It is a 2015 4Runner Trail. Bone stock except for tires and shocks. Thanks!

 

[RichardZ]

Might be a case were the addition or a battery disconnect might be suitable. Save the battery, and anti theft.

This might be my final solution...

 

[ka9mnx]

Maybe your Runner is chatting too much with the mother ship.