Ecu=no power

Supra_Villan

needs his car done
Nov 10, 2007
662
0
0
Wellsville MO
My car is nearing completion and i was putting on my final touches. A friend of mine came out a week or so ago to install my afc and wire my wideband and gauge up for me. He is an electronics wiz and is by no means amateur, he just installed the aem fic on his wife's turbo saturn with no previous reference to go by (he was the first person to do this) and the install was a success, the car runs awesome. That being said, he wired everything up and double checked all connections, and we did the KS rewire while we were at it. We could not verify that things were hooked up correctly at the time because my batt. was dead, so i got the batt. charged up and he checked it with the multimeter and it had 12v so everything was good there. I did the starter relay mod, and the motor cranks over just fine. I have full lights in the interior also, but i noticed when i turn the key to the "on" posisiton, the afc, nor the widband would not illuminate. He tapped into one of the switched 12v on the ecu for the power sources to these. So he figured the ecu was not getting any power, so he took the multimeter, and this was indeed true, i checked the fuses under the hood with the multimeter and everything turned up fine. I have all of my grounds in place, (to my knowledge) my intake manifold is powdercoated, but before i put the two intake manifold grounds on, i took the sanding wheel and my dremel to the bolt holes and knocked them down to the bare metal so that should not be a problem. I also did the fuel pump relay mod some time ago, and i also noticed that i did not get the signature "walboro whine" i though i was supposed to get after doing the 12v mod whenever i turn the key on. I made sure to loop the connector after removeing the fuel pump relay, just as the write up said to do. But i think i just need to double check my wiring, because i did this myself some time ago and the car hasn't ran yet for me to verify that i did it right. I just dont really see what the issue could be here, because the car started and ran just fine before the build, now its doing this. I did swap out my old harness for a newer one in better shape because my old one was quite brittle, the car is an 89 5speed turbo, with the grey plug 89 ecu, and the harness is a grey plug also, i'm sorry its sooooo long, but i wanted to provide all of the clues i've had, hopefully i just FAIL, and this is an easy fix, any and all help is appreciated, thanks.
Charles
 

Supra_Villan

needs his car done
Nov 10, 2007
662
0
0
Wellsville MO
i did do a search btw(ecu* power) but that didn't get me anything. So then i went to google and tried "7mgte ecu no power" and go nothing there. We looked through my tsrm ( i do own one) and had my friend do a once over on the wiring diagram for the tccs in the back of the tsrm and we couldn't get anything from it.
 

Supra_Villan

needs his car done
Nov 10, 2007
662
0
0
Wellsville MO
I just went out and checked all the kick panel fuses today, and they're all good.....i'm not sure what the issue is. I hit the intake ground bolt holes with a light and they showed to be bare metal, i took off the ring terminals and hit those with the dremel too to knock off any "oldness" lol. I'm at a loss guys..... Any input anyone?
 

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
Appears you're having a conversation with yourself here. I suggest you get the electronics wiz who is by no means an amateur back to look at the car because the circuits involved are not difficult. And tell him another wiz who is by no means amateur says it's 1) easy to check if things are hooked up correctly without a battery and 2) it's dumb to connect ancillary devices to critical circuits...
 

Supra_Villan

needs his car done
Nov 10, 2007
662
0
0
Wellsville MO
he is actually leaving for Baghram Air Base Afghanistan soon, so his time is very limited to help me, he's gotta spend time with his wife and 1 year old daughter, not telling a sob story, but i am just saying that he's most likely not gonna be available to help me. I'm not a whiz by any means, but i'm not stupid. So that i know, why are multimeters bad to use or impractical (not sure which one you were getting at) on critical circuits? Can it damage them? What should i do to track down the problem? Since i don't need the battery, what should i do?
 

anonymic

New Member
Jun 11, 2009
11
0
0
Shippensburg, PA
I think the point JetJock was trying to make is that tapping into an ECU switched +12V power source is a bad idea. You're unlikely to hurt anything with a multimeter unless you're working on an airbag system. If you suck that much power from a low amperage source there might not be enough to run your new equipment and your ECU at the same time. Your electronics should be drawing juice from a power source that is switched from the ignition, preferably through a relay so you can run a dedicated circuit with it's own fuse.

Just my 2 cents.
 

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
Your two cents is dead on other than that circuit can actually supply more than enough power to run his stuff. The problem is if something goes wrong (or the install was badly done) it could bring the EFI system down. Better to connect to something that can afford to be lost...
 

anonymic

New Member
Jun 11, 2009
11
0
0
Shippensburg, PA
jetjock;1342752 said:
Your two cents is dead on other than that circuit can actually supply more than enough power to run his stuff. The problem is if something goes wrong (or the install was badly done) it could bring the EFI system down. Better to connect to something that can afford to be lost...

I'll admit that I'm not familiar with MKIII ECU wiring, but I've heard "Oh shit yeah, that'll be just fine" usually followed by the release of the magic smoke one too many times. Thanks for the correction.
 

dumbo

Supramania Contributor
Jul 16, 2008
1,911
0
0
Albera, Too Far North
Because its a switched 12V? So does the Maft, hell, I got my boost gauge, and AFR gauge on it too, with no ill effect. Not saying its the proper thing but it works.

Your problem is quite simple, check for a open in the circuit.