ECU-B Causing Battery Drain?

Hey, I'm wondering if anyone else has had and issue with the body ECU/Body Control Module causing a parasitic drain on the battery?

With the truck completely powered down I have a .25 amp draw on the battery that I have narrowed down to the ECU-B. If I pull the fuse to the ECU-B the draw drops to a more normal 10-20 milliamps and stays there when I put the fuse back in until I do something to trigger the ECU to "wake up", like open the door.

I know the ECU-B controls a lot of stuff so what I am wondering is if anyone else has had this issue and if so was the ECU-B bad and had to be replaced or did it end up being a different end system?

 

u may have to give it about 20 mins for the ecu's on the truck to go into sleep mode. the amperage will be high when you first monitor it then after several minutes u will see the amps begin to drop lower and lower. longest i had was on a lexus took 3 hours to drop down to normal. But if it is good first check any after market conenctions to the truck such as trailer harness, remote starts/alarms. also check all interior lights to make sure they are all off and the door ajar is not staying on.

- check if vehicle has a hood latch switch like a door ajar switch it. If it does that needs to be in the closed position during testing
- make sure all lights are off and doors closed ( if you need the door open to inspect and test inside vehicle remove the t30 bolt from the door ejar switches and to break the ground connection( pull on the sensor a little to make sure it doesn't make contact with the body and let it hang by the connector.
- make sure keys/remote's are far away from vehicle so it will not keep trying to detect it ( especially if it is a smart key, the immobilizer ecu will stay active because it keeps detecting a key present within its zone )

anything under 50 milliamps is normal on a non-smart key and anything under roughly 150milliamps is normal on a smart key

 

Yeah, I checked the door switch, it is all good. It is definitely something to do with the ECU-B though because if I pull the fuse when I park it the truck fires up just fine but if it sits for a few hours with the fuse in it will struggle to start. I suspect this has been an issue for a while but the battery was strong enough to keep if from being noticeable until it sat for a few days and finally drew the battery down enough to have a hard start and the hard cycling of the battery has finally taken it's toll to where it can't maintain a charge with this parasitic drain. This is the second battery in the truck in 5-1/2 years and the first one only lasted about 3 years, this may have been why.

I just need to get some time this weekend to dive into it, I hope it's not a bad unit as they appear to be spendy but I guess that would be a fairly easy fix as well.

 

This is everything that fuse controls, obviously you can rule some out depending on your trucks options. But just make sure when you dive into it to let the vehicle sit for a while with the milimeter connected and come back to it after an hour or so to confirm you deff have a draw. You dont wanna do all this work just to find out your battery is just bad.

A-TRAC
ABS (Hydraulic Booster Type)
ABS (Vacuum Booster Type)
Air Conditioning
Auto LSD (Hydraulic Booster Type)
Auto LSD (Vacuum Booster Type)
Charging
Combination Meter
Condenser Fan
Cruise Control (1GR-FE)
Cruise Control (2TR-FE)
Downhill Assist Control
Electronically Controlled Transmission and A/T Indicator (1GR-FE)
Electronically Controlled Transmission and A/T Indicator (2TR-FE)
Engine Control (1GR-FE)
Engine Control (2TR-FE)
Engine Immobiliser System (1GR-FE)
Engine Immobiliser System (2TR-FE)
Front Fog Light
Ground Point
Headlight
Hill-Start Assist Control
Horn
Ignition
Light Auto Turn Off System
Multi Mode 4WD
Power Outlet (120V)
Power Source
Rear Differential Lock (4WD)
Seat Heater
Shift Lock
Starting
Stop Light
TRAC
Taillight
Trailer Towing
Turn Signal and Hazard Warning Light (w/ Daytime Running Light, w/ Trailer Towing)
Turn Signal and Hazard Warning Light (w/o Daytime Running Light w/o Trailer Towing)
VSC (Hydraulic Booster Type)
VSC (Vacuum Booster Type)
Wireless Door Lock Control

 

Oh is that all?

I was just out playing with it again and it looks like the drain drops off about 2 minutes after the door is shut so it's possible I am chasing a non issue here and my die hard battery just decided to give up like Sears did. I'm going to dig up my paperwork and see if it's been less than 3 years and just have them replace it.

 

Well, the plot thickens. I took the battery in to Sears yesterday and they verified that it was no good and gave me a new one under warranty (11 days from the end of warranty ) so I was ready to assume everything was now good. This morning I went to to start up and found that the immobilizer light is flashing again (usually a sign of battery voltage less than expected by immobilizer system) so I am suspecting I may still have some kind of issue. Truck fired right up, no issues and light stopped blinking but I still find it suspect, especially with a brand new battery.


Edit: Or maybe after doing a little research that light always blinks. For some reason I don't remember it blinking all the time but it's probably something I never really paid attention to until I became focused on every little electrical thing going on with the truck.

 

If your referring to little red blinking light on dash. It always binks

 

Yeah, you're right after some research I confirmed what I used to know but forgot. I just got so hyper-focused that I started paying attention to things I had long since learned to ignore. My girlfriends car had a bad battery a while back and the immobilizer light would blink all the time until we replaced it and I had that memory fixed in my head convincing me there may still be an issue. The power of an idea is a very strange thing.

 

My yaris do the same .. i dont know if the ecu-b fuse draw the battery, now i am trying with another one .. my opinion its normal the 0.12 amp in that fuse for a one our or something