No start after pulling the mir relay.

[Rob37072]

Originally Posted by steve99

You should be able to talk to ecu via obd port (ie can buss) with just earth 12v and ignition 12v supplied to ecu.


Check all ecu fuses

Yes, it's clear to me the car is missing either

12v to ECU
switched 12v to ECU
a functional ECU.


I did have an OBDII dongle plugged in at the time. Maybe some black magic sent full voltage across OBD pins that shouldn't have?

I don't have a setup to test the ECU externally from the car.

[Rob37072]

Originally Posted by Razorlor

Alternator bolt and battery positive. It is positive to positive, but it is called voltage drop testing. Easy way to determine if a fuse/fusible link is blown without visually inspecting it.

A meter tells you the different between the two leads. If you go positive to positive and show a difference of 12 volts, it isn't making it to where it should be.

Oh DUH Obviously... so I was right not to expect voltage.

The radio, headlights, locks and windows all work. I wonder if they come off the other side...

Doing more digging but if either of those links is blown i shouldn't have continuity to those nuts right?

[Razorlor]

Right, if it was operating normally, you would expect 0 volts, as there is no difference between the two.

And yes, if the fuse is blown you would see a 12v drop at the fuse.

[Razorlor]

Going over the wiring diagram, the only thing really affected is the alternator fuse (ie, the fusible link on the battery positive block)

[Rob37072]

Originally Posted by Razorlor

Right, if it was operating normally, you would expect 0 volts, as there is no difference between the two.

And yes, if the fuse is blown you would see a 12v drop at the fuse.

a video is worth about 10,000 words.

[ame]https://www.youtube.com/watch?v=zZoeBcdFhCA[/ame]

I don't understand why i would see 12v to that post on the starter from the positive battery terminal BUT there is definitely continuity across the links. Testing to each nut shows no voltage and the continuity tester beeps and goes to zero.

[Razorlor]

Resistance (continuity testing is best done with things unplugged as it sends voltage out of the meter, this can damage the ECU, it usually won't though, so no worries), but that confirms the fusible link isn't blown. And a visual on them in the video agrees.

Hmmm, not sure where to go from there...

Also worth mentioning. The bolt you were showing was the starter, not the alternator. But that isn't needed anymore, so don't worry about it.

[Rob37072]

Originally Posted by Razorlor

Resistance (continuity testing is best done with things unplugged as it sends voltage out of the meter, this can damage the ECU, it usually won't though, so no worries), but that confirms the fusible link isn't blown. And a visual on them in the video agrees.

Hmmm, not sure where to go from there...

Also worth mentioning. The bolt you were showing was the starter, not the alternator. But that isn't needed anymore, so don't worry about it.

Jeeze... my issue is reading comprehension not mechanical prowess. I TOTALLY know the difference between the alternator and starter. Everyone else in the thread has been talking starter so my brain just flipped your "alternator" request to "starter"

I think i'm getting too old and/or tired to work on cars.

[Razorlor]

Can you take a picture of the underhood fuse box, relays and all?

[Rob37072]

Originally Posted by Razorlor

Can you take a picture of the underhood fuse box, relays and all?

Sure can. I do feel like maybe I put it back in the wrong place but other images I've looked at seem to have the relays in the same place.

[Razorlor]

You are missing the ignition 2 relay, I don't know where it is, but that is 100% your problem.

[Razorlor]

You must have pulled another relay, there isn't one in the wrong place that I can see. Maybe it is on the cowl or inside the car? You can always move the mirror heater relay into the ig2 spot and make sure everything works.

[Rob37072]

Originally Posted by Razorlor

You must have pulled another relay, there isn't one in the wrong place that I can see. Maybe it is on the cowl or inside the car? You can always move the mirror heater relay into the ig2 spot and make sure everything works.

I think that's a BRZ thing for the push button start. I thought it was weird that that was missing but I definitely didn't throw a relay away.

I'll try it... i think the fan relays have 1 extra pin.

[Razorlor]

FR-S shows the same.

[Rob37072]

Originally Posted by Razorlor

You must have pulled another relay, there isn't one in the wrong place that I can see. Maybe it is on the cowl or inside the car? You can always move the mirror heater relay into the ig2 spot and make sure everything works.

F*&$ my life... that's what it was. I *thought* my car was super base and didn't think it even had heated mirrors...

Thanks man...

I am DEFINITELY getting old... 15 years ago I could do this stuff in my sleep.

So the root cause was that I read the fuse box diagram incorrectly before i pulled ANYTHING. So when i went to put it back where it goes I put it in where i had read that i pulled it out... which was wrong.