Reply With QuoteHow is power to the ECU wired?
Should have a constant 12v, and two ignition switched 12v supplies.
Calling electrical gurus !!
So I have a problem of my battery going flat overnight. Car is. Ke70 with a 4age.
Straight to the point my battery is new and nothing wrong with it charges and cranks fine. I have worked out that I have excessive parasitic draw about 5 amps.
I have found the circuit it's on and it's the ECU which is the problem. When I pull the ecu fuse the amps drop to nothing (approx 30miliamps)
the car runs fine so I would assume the ecu is ok.
now I know where the problem is... How do I go about correcting it ? This might be silly but Could it be that my ecu is mounted the body.. I.e ground !!??
I' don't have the best knowledge with electrical stuff and this is where my talent runs out !
Could any one please help out with a suggestion or 35..
CHEERS!!!
How is power to the ECU wired?
Should have a constant 12v, and two ignition switched 12v supplies.
That it does..
Are the injectors powered off batt or ign?
Can't remember that one Ill have to check the wiring diagram. Would this be contributing to the problem u think?
Ugh. Just go disconnect the injectors and see if the draw goes away.
The Toyota way is that the ECU triggers a relay that powers up the injectors. They probably had a reason for that. I've never done that and just wired it to the black/orange. Maybe your guy skipped that and gave it straight battery.
Last edited by Skylar; 25th June 2014 at 10:53 PM.
^^Just had a look at the AE82 4AGE wiring diagram, in that instance the ECU does NOT trigger the EFI relay. It's triggered by the ignition switch. The only relay triggered by the ECU is the COR (fuel pump double trigger relay -positive trig under STA, -ve trig from ECU for prime (on some ecus) and when it's got an RPM signal).
It all really depends how the 4AGE has been wired in. A quick look through my AE82 schematics shows that the the only real potential cause you have is that your ECU has been wired in with B+ constant voltage where it should have switched ignition voltage. I've seen some real wiring hackjobs in my time so it's not beyond the realms of possibility.
Even if your injectors are 'hot' all the time, the ECU provides the ground path so they will not be drawing current as there is no complete circuit.
Last edited by Javal; 25th June 2014 at 11:17 PM.
You can have any brew you want... as long as it's a Datsun / Corolla / What is that?
Sorry, I knew there was a relay between the supply and the injectors. Been years since I wired one.
I always wondered about whether there would be a 'leak' through that path if the injectors were powered all the time. Nissan do their injectors on batt but they also do have an ECU Switched relay so I wondered if the injector circuit was powered only through that. I've read at least one ECU manual that says to not power the injectors off batt so there must be something bad with it and I can only think of it creating a draw when ECU is off.
Aside from injectors, the only thing that's really powered (and hungry) when engine runs is coil, fuel pump or injectors. The sensor circuits only get voltage when the ECU has power. ECU only draws a coupla amps at most (but sinks a lot more). Could the coil be wired to batt?
Disconnect your ecu plugs and see if you still have 5 amps, that'll rule out the ecu being the source of the draw.
Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners
Sounds like you've got a pretty good lead on it if you know it's something on the ECU circuit that's drawing 5A. That's a fair bit, so shouldn't be too hard to find. Just work through everything that's run off that fuse.
I wouldn't be surprised if it isn't the ECU itself that is pulling the current. To have that much current draw, but otherwise work perfectly sounds unlikely.
Hen
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