Can ECU drain battery?!
Thread Starter
Driver School Candidate
Joined: Dec 2019
Posts: 9
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From: Ca
Can ECU drain battery?!
Hello there!
I have a parasitic drain of 500 mili-amps. Checked with a multi meter between neg cable and post. Started pulling every fuse in engine and under driver dash area to only find the ecu-b and “short” fuses are the only ones drawing current.
started thinking of any known issues that may cause this drain. My driver side master window switch has been intermittently working for both the front windows so I unplugged the damn thing and it reduced the draw to 300 mili-amps.
next I had an after market reverse sensor system installed, so I unplugged that damn thing, but this time no affect.
can my ecu be bad and cause the rest of the draw? Please share any info or similar experiences you had! Thank you!
I have a parasitic drain of 500 mili-amps. Checked with a multi meter between neg cable and post. Started pulling every fuse in engine and under driver dash area to only find the ecu-b and “short” fuses are the only ones drawing current.
started thinking of any known issues that may cause this drain. My driver side master window switch has been intermittently working for both the front windows so I unplugged the damn thing and it reduced the draw to 300 mili-amps.
next I had an after market reverse sensor system installed, so I unplugged that damn thing, but this time no affect.
can my ecu be bad and cause the rest of the draw? Please share any info or similar experiences you had! Thank you!
Pole Position
Joined: Dec 2019
Posts: 2,993
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From: The Jet City
If your vehicle runs, why would you think the ecu/pcm be bad? You have a clock, radio presets, ect.....Did this just start or what? Hows the condition of the battery? How old is the battery?
Lexus Champion
Joined: Apr 2019
Posts: 11,126
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From: FL
What is your Year/ Model and mileage?
Next question can you set your alarm and hear the normal beeps when using your FOB?
The RX330 uses both Aluminum electrolytic and Tantalum capacitors in the ECM.
In my experience working on circuits for many years I have seen Tantalums pull current when they fail kinda like a draw(very rare) but the Tantalums in my ECM were rock solid at 16 yrs old.
However the Aluminum caps were beginning to fail but they die differently and wouldn't have the symptoms of draw.
If I was a betting man(and sometimes I am lol) I would look somewhere else for the draw and the ECM as last resort but yes it is possible since there is a low power circuit that "Keeps alive" so it can know to unlock doors, etc. But if you have anything not letting it "hibernate" after setting alarm it will draw extra current.
Next question can you set your alarm and hear the normal beeps when using your FOB?
The RX330 uses both Aluminum electrolytic and Tantalum capacitors in the ECM.
In my experience working on circuits for many years I have seen Tantalums pull current when they fail kinda like a draw(very rare) but the Tantalums in my ECM were rock solid at 16 yrs old.
However the Aluminum caps were beginning to fail but they die differently and wouldn't have the symptoms of draw.
If I was a betting man(and sometimes I am lol) I would look somewhere else for the draw and the ECM as last resort but yes it is possible since there is a low power circuit that "Keeps alive" so it can know to unlock doors, etc. But if you have anything not letting it "hibernate" after setting alarm it will draw extra current.
Thread Starter
Driver School Candidate
Joined: Dec 2019
Posts: 9
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From: Ca
It’s a 2008 rx350 v6 fwd just under 100k mileage.
ive owned the car for only a couple months and found this drain after battery died after a week. Usually dies if not drivin in a 24hr period.
battery is new as I’ve replaced it. Also load tested it with good results. terminals are clean too.
Only other thing I can think of checking is the rear window water nozzle sprayer motor thingy ma jig. As it no longer operates. Other than that, I’m a chicken running without a head.
ive owned the car for only a couple months and found this drain after battery died after a week. Usually dies if not drivin in a 24hr period.
battery is new as I’ve replaced it. Also load tested it with good results. terminals are clean too.
Only other thing I can think of checking is the rear window water nozzle sprayer motor thingy ma jig. As it no longer operates. Other than that, I’m a chicken running without a head.
Thread Starter
Driver School Candidate
Joined: Dec 2019
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From: Ca
Actually! I don’t hear the first beep when unlocking just the driver door, only hear the second beep when unlocking all doors. I’ve never owned a Lexus, is this normal? Other than that, all other sounds are there while arming and disarming the car. The Alarm works as well.
While I have never heard of an ECU draining a battery, it could be possible in theory, especially if the whole ECU is going bad, but other wonky things will occur.
But this does not add up. I have an aftermarket Viper Remote Start on my RX and can leave it for 2-3 weeks with no issue. I haven't done a parasitic drain test but I assume the Viper has gotta be drawing 200-300mA to keep the antenna on.
Anything else aftermarket on your RX?
But this does not add up. I have an aftermarket Viper Remote Start on my RX and can leave it for 2-3 weeks with no issue. I haven't done a parasitic drain test but I assume the Viper has gotta be drawing 200-300mA to keep the antenna on.
Anything else aftermarket on your RX?
Lexus Champion
Joined: Apr 2019
Posts: 11,126
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From: FL
Agree with Lexuswiz if your battery is good and you have a parasitic draw something is on but you are only pulling 6 watts for the ECM, Body ECU, and Driver Door ECU, etc to stay alive it doesn't sound like much but I don't know.
How much is normal anyone done a draw test?
How much is normal anyone done a draw test?
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Thread Starter
Driver School Candidate
Joined: Dec 2019
Posts: 9
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From: Ca
While I have never heard of an ECU draining a battery, it could be possible in theory, especially if the whole ECU is going bad, but other wonky things will occur.
But this does not add up. I have an aftermarket Viper Remote Start on my RX and can leave it for 2-3 weeks with no issue. I haven't done a parasitic drain test but I assume the Viper has gotta be drawing 200-300mA to keep the antenna on.
Anything else aftermarket on your RX?
But this does not add up. I have an aftermarket Viper Remote Start on my RX and can leave it for 2-3 weeks with no issue. I haven't done a parasitic drain test but I assume the Viper has gotta be drawing 200-300mA to keep the antenna on.
Anything else aftermarket on your RX?
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Thread Starter
Driver School Candidate
Joined: Dec 2019
Posts: 9
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From: Ca
Thread Starter
Driver School Candidate
Joined: Dec 2019
Posts: 9
Likes: 2
From: Ca
Thanks to everyone whom tried to help. After over coming procrastination, I finally made the attempt to replace my master window switch to see if that will solve the issue. It did!!
after receiving the used oem replacement part I’ve ordered, I compared it to the current one I have and it was obvious that the last owner had replaced the switch before but with an after market part.
I’m not knocking on after market parts as they also have their pros but stick with Toyota master window switches if you ever need one.
after receiving the used oem replacement part I’ve ordered, I compared it to the current one I have and it was obvious that the last owner had replaced the switch before but with an after market part.
I’m not knocking on after market parts as they also have their pros but stick with Toyota master window switches if you ever need one.
Driver
Joined: Jan 2016
Posts: 84
Likes: 5
From: Ohio
While I have never heard of an ECU draining a battery, it could be possible in theory, especially if the whole ECU is going bad, but other wonky things will occur.
But this does not add up. I have an aftermarket Viper Remote Start on my RX and can leave it for 2-3 weeks with no issue. I haven't done a parasitic drain test but I assume the Viper has gotta be drawing 200-300mA to keep the antenna on.
Anything else aftermarket on your RX?
But this does not add up. I have an aftermarket Viper Remote Start on my RX and can leave it for 2-3 weeks with no issue. I haven't done a parasitic drain test but I assume the Viper has gotta be drawing 200-300mA to keep the antenna on.
Anything else aftermarket on your RX?
Now I do have a Error#4 on CD player, and have pulled fuse and battery with no luck getting it to go away. Even tried to put radio in 'Ship Mode' with no luck.think changer must have bad band or something.
Thanks in advay if ya can help with advise.
Sean
Im having a similar prob.with my 04 RX 330. I've had the car 5 years now, and have replaced the battery 2x's.i have a 500ma draw as well with the draw coming from the ECU-B fuse. My windows work when the car is off and locked.my dog can open the windows when she's in it and I'm in the store. I tested it, I locked the doors with car off and windows down. Hour later I reached in and rolled up the windows up with the switch. I have my alarm set to NON passive via techstream so alarm didn't go off.but the windows are still active after an hour of being off. Is there a master controller somewhere for windows other than the master switch? I could just get a used oem one if the mater switch also acts as the window controller. Have had some other issues occasionally. The battery light comes on or one of the headlight leveling motors get hung up. Always been able to reset with pulling neg battery cable to fix problem.
Now I do have a Error#4 on CD player, and have pulled fuse and battery with no luck getting it to go away. Even tried to put radio in 'Ship Mode' with no luck.think changer must have bad band or something.
Thanks in advay if ya can help with advise.
Sean
Now I do have a Error#4 on CD player, and have pulled fuse and battery with no luck getting it to go away. Even tried to put radio in 'Ship Mode' with no luck.think changer must have bad band or something.
Thanks in advay if ya can help with advise.
Sean
Radio might be a goner, I've seen a few cases with Error 4, luckily these cars are aging and used radios are cheap or even aftermarket to get carplay/android auto.
Driver
Joined: Jan 2016
Posts: 84
Likes: 5
From: Ohio
Few things for the windows, doubt it the master switch itself. Has more to do with the BECU going to sleep. In techstream what is your program for shutting off the BECU? Instant door trigger, 30 sec from key out ignition, or 60 sec key out ignition?
Radio might be a goner, I've seen a few cases with Error 4, luckily these cars are aging and used radios are cheap or even aftermarket to get carplay/android auto.
Radio might be a goner, I've seen a few cases with Error 4, luckily these cars are aging and used radios are cheap or even aftermarket to get carplay/android auto.
As for the radio, it works, just the CD player is gone..shows it loaded up with CD's (it's not) and error #4 when I try to go to CD...I Neve use CD's anyway.
Thank you again for the help.
Sav
(Only thing I remember setting time limit on was exterior lighting I believe..to 15sec maybe or 30) I will plug it in latter today if I have time.
Nah, this gen RX is fairly simple, v13 is more than enough.
That exterior lighting setting is basically the sleep/shutdown trigger. Maybe my times are off but it could along the lines of instant, 15, 30, 60 sec.
That exterior lighting setting is basically the sleep/shutdown trigger. Maybe my times are off but it could along the lines of instant, 15, 30, 60 sec.