No power to the ecu...........again

[Bigzavs]

well guys, i was out in my supra tuning on 8psi, and everything is going fine, car is running strong. after about 5 miles, i come to a stoplight and the car dies on me, im thinkin o well, its probably nothing, well car doesnt restart, i try so much crap tryin to figure it out that i kill the battery from cranking. my mom brought cables and we hook it up, and i notice that the SAFC isnt coming on, and ive got the jumper on to pull codes, and im not even flashing the CEL. ive got no power to the ecu again.

i had this problem last year, engine harness is good, we tested the continuity on the wires that would cause the problem, nothing wrong on the harness.

i was having charging issues a month or so back, so i swapped the front body harness out, after that no problems. then this BS happens.

im thinking i need to swap out the behind dash harness with the fuse panels and all. theyve always been iffy on the car and im wondering if they could possibly be a culprit. (iffy as in if the panel gets bumped by my left foot, the radio shuts off).

BTW, when i was trying to get it started, i jumpered pin 2 and pin 12 on the T connector (Battery and Switched Battery respectively) and i can power up my SAFC.

Also, could a dead battery possibly be the cause of all this? after i took it off the jumper cables, it cranked maybe 3 times at 5 seconds each time before it was nearly dead again, barely turning over.

 

[GrimJack]

I hate to point out the obvious... but you did check the fuse first, right?

 

[Bigzavs]

yessuh, just fine i checked every fuse i could with the minimal lighting i had where the car was

 

[tissimo]

ECU is powered by the engine bay wiring harness (through the fuse box connector) so it will not be the interior wiring. Have you checked the engine grounds (on the intake manifold) to make sure they're good? Also check the ground on the left fender under the fusebox.

Grab a volt meter and start tracking it down.

 

[Bigzavs]

weird thing is, ive driven the car as is for a couple weeks b4 this, just short distances w/o any problems. ive just changed from a USDM 2J ecu, to a stock 1J to a JDM 2J ecu now. only other thing ive done is wire my walbros up to a relay for each of them. thats it, but ill start lookin and checkin tomorrow, too cold outside and im too pissed at the car to work on it right now

 

[tissimo]

If you can jump power to the system (through check connector) then its not the ECU grounds (intake manifold). I cant find anything on the check connector (wiring diagrams) to see where the Diag connector gets continuous power from (didn't know it had it to be honest) though.

But if that works and powers the afc then its probably a main relay issue. Check the Ground under the fusebox to make sure its making a good connection. If thats good start looking into the main relay and see if its getting power, also check the relay its self as well if everything else checks out.

 

[Bigzavs]

i jumpered it on the wiring harness near the ecu, lil trick a friend taught me last time this happened. while i had the key turned over, i can say this, the main relay wasnt warm at all, usually gets pretty hot but it didnt this time

 

[Bigzavs]

when i went into the fuse box today with a test light, with the key turned 2 clicks i got power across the efi fuse, and one prong of the main relay showed switched power, but the B+ wire on the C1 connector is not getting any power whatsoever still. i gave that wire a straight 12v source off the battery, and i got power back to the safc and the B+ pin on the ecu connector. so the wire isnt shot. in the morning im gonna go get a new dash harness and fuse panels at a junkyard and swap them out, cuz its the only part of that circuit of fuses, relays, body harness and engine harness that i havent changed out and/or tested. (i tested 4 different main relays, none worked). so hopefully maybe possibly itll work.

 

[slidingsidewayz]

i have that exact same problem where the B+ switch pin wasn't getting any juice. i never got around to solving that problem so i just made my own relay to power the B+ pin. keep us posted on what that problem could be.



fred

 

[Bigzavs]

turns out if was the 2J ecu that was causing the problem.

once i put in a stock 1j ecu, car started right up, id plug the 2j back in after that, and itd run again, but if i let it sit while it was off with the 2J ecu, it wouldnt start back up, just crank and crank

 

[Bigzavs]

well, im on the brink of torching the car, the alt power cable touched metal and arc'd out, burnt up the fusible link in the process, replaced that, and changed my plugs while at it. now the car doesnt want to charge.....at all, before this i was over 14v's coming out, now im under 12 at idle, car barely runs, idles completely off the wideband on lean. i tried to test continuity on the alt wires, but im not sure i did it right (one probe on each end of the wire and the meter set on ohms? i never do wiring) when i did that i showed .4, .5, and .8 on the wires, shouldnt they be zero? and if it is supposed to be that, is it possible that i fried the wires when the cable arc'd?

 

[suprahero]

I wish I could help you Ben, but I'm an electrical idiot.

 

[Bigzavs]

I wish I could help you Ben, but I'm an electrical idiot.

just this past sunday i had a really good electrical guy lookin at my car, but of course, the car decided it would charge that day.....:cry:

im an electrical idiot as well

 

[suprastanger507mgte]

your chances are very good of frying any one of the alternator wires.
Also, your alternator could have taken a crap as well. You can get that tested out for free at any Auto parts store.

 

[Bigzavs]

your chances are very good of frying any one of the alternator wires.
Also, your alternator could have taken a crap as well. You can get that tested out for free at any Auto parts store.

ya, after talking with the local electrical guru, he said to make a harness on its own to go to the alternator, completely bypassing the engine harness, as it probably fried the wires. if that didnt work, he said go get the alt tested out and then if all that doesnt work, hes gonna come down on his day off and we'll (he will moreso) figure out whats wrong with it.

 

[suprahero]

and then if all that doesnt work, hes gonna come down on his day off and we'll (he will moreso) figure out whats wrong with it.

:biglaugh:

 

[str8_6]

i am pretty sure its the positive wiring going to the alternator. i remember you had an issue with that.

i had an issue with the nut that holds it onto the alternator...it arched and got more and more brittle... you should def redo those wires..i think its only like 2 or 3 wires. at least thats what i redid and it ran fine eversince. check that nut i was talking about too and make sure it isnt all melted.

 

[Bigzavs]

ya, it turned out to be the wiring to the alternator, its somewhere in the loom, so i didnt bother, i just made a harness for it by itself. car charges back where it was now

 

[Bigzavs]

:biglaugh:

ya, we'd technically both be looking over the car, but he'd have actually been doing the work, i probably woulda been sitting wondering wtf hes doing. luckily i didnt need to drag him 55 miles south on his day off today to look at it