GS300 battery drain solution
07-04-17, 02:45 AM
#1
Driver School Candidate
Thread Starter
GS300 battery drain solution
Hi, new member. 2002 GS300.
A while back I started getting a 600 ma parasitic current draw when the car is off. This is enough to drain the battery in about a day.
For the time being I just installed a battery switch but now i'm trying to diagnose it.
The underhood ECU-B1 fuse removal reduces the drain to 50 ma.
I found a PDFon scribd which seems to be GS wiring diagram (might not be the right year) that shows the ECU-B1 circuit branched off to the
DOME and ECU-B2 fuses. Pulling the ECU-B2 fuse also reduces the drain to 50 ma.
Now the puzzling thing is my manual and the pdf both say this is for the driver's power seat ECU.
But the seats both still work with the fuse out!
The only thing I notice is after restarting the car the system doesn't remember the state of wheel telescoping and air conditioner settings,
although they both work fine.
Does someone have the wiring diagram for a 2002 GS300? It seems like ECU-B2 fuse is for a body control ECU or something.
I'd like to get this sorted.
Thanks
Les
A while back I started getting a 600 ma parasitic current draw when the car is off. This is enough to drain the battery in about a day.
For the time being I just installed a battery switch but now i'm trying to diagnose it.
The underhood ECU-B1 fuse removal reduces the drain to 50 ma.
I found a PDFon scribd which seems to be GS wiring diagram (might not be the right year) that shows the ECU-B1 circuit branched off to the
DOME and ECU-B2 fuses. Pulling the ECU-B2 fuse also reduces the drain to 50 ma.
Now the puzzling thing is my manual and the pdf both say this is for the driver's power seat ECU.
But the seats both still work with the fuse out!
The only thing I notice is after restarting the car the system doesn't remember the state of wheel telescoping and air conditioner settings,
although they both work fine.
Does someone have the wiring diagram for a 2002 GS300? It seems like ECU-B2 fuse is for a body control ECU or something.
I'd like to get this sorted.
Thanks
Les
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turtelshea (10-30-19)
07-04-17, 09:05 AM
#2
That seat ECU remembers the positions of the seat and probably the steering wheel. The seat motors themselves are on a different circuit. If you've pulled the ECU-B2 fuse and the drain stops, you're definitely looking in the right area. Body ECU 2 is attached to the back of the driver's side kick panel fuse box.
07-05-17, 02:09 AM
#3
Driver School Candidate
Thread Starter
Well, I found the electrical diagrams for 1999 GS here on this site. It's more readable than the scribd repair manual diagrams.
The power seat ECU has two fused power inputs...the motor controls (B+) and communication/logic section (sysB). When I pull the
ECUB2 fuse to stop the drain I'm just depowering sysB which is why the seat still works. Now the seat talks to the body ECM2 and it talks
to tilt/telescope ECM and AC, so that explains why the start up memory settings don't work on those.
This makes the body ECM2 highly suspect as causing the battery drain. I note that I'm not depowering it when I pull the fuse...I just am not letting the seat talk to
it. I need to do a bit more diagnostics to find out whether the ecm is bad or something else is telling it the wrong thing.
I'll keep documenting what I find since if it happened to my car it must happen to many others. A search shows this is true, and dealer techs usually cannot
find the problem...making the car a write off.
Les
The power seat ECU has two fused power inputs...the motor controls (B+) and communication/logic section (sysB). When I pull the
ECUB2 fuse to stop the drain I'm just depowering sysB which is why the seat still works. Now the seat talks to the body ECM2 and it talks
to tilt/telescope ECM and AC, so that explains why the start up memory settings don't work on those.
This makes the body ECM2 highly suspect as causing the battery drain. I note that I'm not depowering it when I pull the fuse...I just am not letting the seat talk to
it. I need to do a bit more diagnostics to find out whether the ecm is bad or something else is telling it the wrong thing.
I'll keep documenting what I find since if it happened to my car it must happen to many others. A search shows this is true, and dealer techs usually cannot
find the problem...making the car a write off.
Les
02-03-19, 12:06 PM
#4
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Location: FL
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Well, I found the electrical diagrams for 1999 GS here on this site. It's more readable than the scribd repair manual diagrams.
The power seat ECU has two fused power inputs...the motor controls (B+) and communication/logic section (sysB). When I pull the
ECUB2 fuse to stop the drain I'm just depowering sysB which is why the seat still works. Now the seat talks to the body ECM2 and it talks
to tilt/telescope ECM and AC, so that explains why the start up memory settings don't work on those.
This makes the body ECM2 highly suspect as causing the battery drain. I note that I'm not depowering it when I pull the fuse...I just am not letting the seat talk to
it. I need to do a bit more diagnostics to find out whether the ecm is bad or something else is telling it the wrong thing.
I'll keep documenting what I find since if it happened to my car it must happen to many others. A search shows this is true, and dealer techs usually cannot
find the problem...making the car a write off.
Les
The power seat ECU has two fused power inputs...the motor controls (B+) and communication/logic section (sysB). When I pull the
ECUB2 fuse to stop the drain I'm just depowering sysB which is why the seat still works. Now the seat talks to the body ECM2 and it talks
to tilt/telescope ECM and AC, so that explains why the start up memory settings don't work on those.
This makes the body ECM2 highly suspect as causing the battery drain. I note that I'm not depowering it when I pull the fuse...I just am not letting the seat talk to
it. I need to do a bit more diagnostics to find out whether the ecm is bad or something else is telling it the wrong thing.
I'll keep documenting what I find since if it happened to my car it must happen to many others. A search shows this is true, and dealer techs usually cannot
find the problem...making the car a write off.
Les
Great T/S, most people cannot properly use a multimeter...
04-22-19, 08:22 PM
#6
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Location: FL
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2000 gs300 in otherwise good condition doing same thing, draining in about a day with battery connected. I can use a meter just have not started yet.
What fixed his? I am thinking he can drive with ECUB2 fuse pulled??
What fixed his? I am thinking he can drive with ECUB2 fuse pulled??
10-30-19, 06:40 AM
#7
Driver School Candidate
ECU-B2 Fuse 5 amp
Hello I to seem to be having the same problem with the ECU-B2 fuse my remote central locking stopped working and my battery was draining overnight the power lock switch would not work on the driver's door or passenger door and no dome light when you opened any door I have now removed the 5amp ECU-B2 fuse and everything is now working.
Is it safe to drive the car with the fuse removed?
Should I replace the ECU-B2 or just leave the fuse out?
Is it a big job to replace?
And is any year better than mine 1998 gs300 can it be repaired or should I just purchase a new one.
Thanks for any advice you can offer
Is it safe to drive the car with the fuse removed?
Should I replace the ECU-B2 or just leave the fuse out?
Is it a big job to replace?
And is any year better than mine 1998 gs300 can it be repaired or should I just purchase a new one.
Thanks for any advice you can offer
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