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Electrical issue after injector re-pin
Electrical issue after injector re-pin
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Old 09-07-19, 05:59 PM   #1
UrdnotWrexSTi
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Default Electrical issue after injector re-pin

So I just got my rebuild done today and started her up. She started missing on cylinder 4 immediately so I shut her off. Fuel was good, so was spark confirmed via multimeter.



So I checked the injector #4 plug and noticed one side of the plug was getting 11-12 volts, the other one was getting 0. I compared to injector #1 which was getting 11-12 volts one on side and 3-4 volts on the other. (I know little about Subaru electrical so I think it's safe to assume it's normal for one side to be getting full voltage and one to be getting low voltage?)



On the #4 injector plug wire that was getting 0 volts I noticed that only 3/4ths on the wire was seated in the plug, so I gave it a light tug and it came out with no effort... So it's safe to conclude that it wasn't making a connection at all, thus why it's 0 volts.



Luckily I had a set of new EV6 plugs from a Injector Dynamics kit I had laying around. So I cut and spliced only the wire that was loose with a new connector and plugged it back into the EV6 plug.



Now the real problem...


The car will not start. The starter wont turn, the fuel pump won't prime and the temp gauge in the dash goes straight to HOT with the key on. No CELs and and Accessport DOES turn on, so the ECM is more than likely still good. My guess is that something shorted somewhere, but like I said I'm not skilled with Subaru electrical so I don't know where else to look for problems.



It's important to note that I did this all while the key was on, with the battery connected. I forgot the unhook the neg terminal from the battery before messing with that plug. One of the loose wires from injector plug that I removed may have come in contact with the steel barb on the manifold for the Brake master cylinder but I can't remember If I heard an audible click somewhere in the engine bay or not. If that loose wire did make contact with that barb, would that be enough to short something out? I checked all the underhood fuses and found nothing burned.



Anyone have any input on where I should start looking? I did check all grounds.
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Old 09-08-19, 04:03 AM   #2
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Default Re: Electrical issue after injector re-pin

Yes enough to short something out. Most likely ECU.

For the moment forget the injector. Start at the starter and work back to the ECU.
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Old 09-08-19, 04:55 AM   #3
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Default Re: Electrical issue after injector re-pin

Oh boy, doing wiring repair with the key on lol. Either you shorted something out or something isnt connected properly. I would first start with the simple easy stuff. Have you tried clearing faults and doing a battery reset first? I would double, triple check ALL grounds! Make sure they are all connected, tight/secured, and in good shape. If this is a GR/GV sti, there are some by the intake manifold, the fender, under the engine ect ect ect. It may also help to bascially retrace your steps of repair to see if you missed anything.

I wouldnt condem the ECU just yet.

Last edited by Jay11STI; 09-08-19 at 05:01 AM.
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Old 09-08-19, 08:26 AM   #4
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Default Re: Electrical issue after injector re-pin

Like I said the car started and ran with no fault codes other than the cylinder #4 misfire just before I found that injector wire loose and I did the repair. The only electrical thing I disconnected was that plug, nothing else was in the way for me to unhook. I rechecked everything in the general area of the repair and everything looked fine. I did unhook the battery for about 10 minutes and hooked it back up and no change. Checked all grounds as well.



I feared the ECM would have been shorted right about when I finished checking everything, but wouldn't there be a fuse or something to protect the ECM from this? How could a small short from an injector wire damage the ECM? I god damn hate electrical......
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Old 09-08-19, 08:57 AM   #5
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Default Re: Electrical issue after injector re-pin

Oh and by the way, now that I am re-checking the injector plugs for power I get no reading at all. Both connectors in the plug give me no reading with the key on... To be sure I'm getting power to the harness at all I checked the coil pack connectors and I AM getting power to those connectors.


So for some reason it's just the injector wires that are not getting power at all now, but everything else is.



After checking alldata I noticed the warning at the bottom saying that you have to use the right ECU when replacing it in order to prevent damage specifically to the injection system... Now that gets me wondering if it can go in the opposite direction... maybe if you short out the wires for the injection system, you can damage the ECU

Screenshot (7) by Ricky Vieira, on Flickr

Last edited by UrdnotWrexSTi; 09-08-19 at 01:04 PM.
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Old 09-08-19, 12:18 PM   #6
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Default Re: Electrical issue after injector re-pin

Quote:
Originally Posted by UrdnotWrexSTi View Post
Oh and by the way, now that I am re-checking the injector plugs for power I get no reading at all. Both connectors in the plug give me no reading with the key on... To be sure I'm getting power to the harness at all I checked the coil pack connectors and I AM getting power to those connectors.


So for some reason it's just the injector wires that are not getting power at all now, but everything else is.



After checking alldata I noticed the warning at the bottom saying that you have to use the right ECU in order to prevent damage specifically to the injection system... Now that gets me wondering if it can go in the opposite direction... maybe if you short out the wires for the injection system, you can damage the ECU
Using the right ecu to prevent damage to injection system really only refers to when you are replacing the ecu. I woulnt worry about this unless you are planning on replacing the ecu.

Since you are still able to communicate with the ecu and are getting power to the coils via the ecu i dont think ecu is bad yet. Injectors are pulse width modulation so you arent going to see the same voltage while in use.

I think you need to look into seeing if a main relay/fuse is the issue. I wish i had a wiring diagram to help. I would suggest looking in the engine fuse box and looking at all the main fuses/relays. Sometimes those main fuses blow real easily.

Last edited by Jay11STI; 09-08-19 at 12:27 PM.
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Old 09-13-19, 07:36 PM   #7
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Default Re: Electrical issue after injector re-pin

Annnnnnd it was just a 15amp fuse in a fuse box under the dash in the passenger footwell... God damn. Looks like it's a fuse for the ECU by the way. So for anyone who happens to short out the wires for the injectors, your ECU will lose communication to the OBDII port. Look for a 15amp fuse next to the blower motor.
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Old 09-14-19, 03:30 AM   #8
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Default Re: Electrical issue after injector re-pin

Awesome! Nice to know that they are so well protected!!!

Thinking about it it now, I'd guess the 12V you shorted was supply. The drive probably pulls low. Also good to know. Should have figured this as it make it easier to protect with just a fuse and far harder to damage even when you get stuff wrong When you short stuff all that normally occurs is blowing a fuse
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Old 09-14-19, 08:53 AM   #9
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Default Re: Electrical issue after injector re-pin

Quote:
Originally Posted by mheyman View Post
Awesome! Nice to know that they are so well protected!!!

Thinking about it it now, I'd guess the 12V you shorted was supply. The drive probably pulls low. Also good to know. Should have figured this as it make it easier to protect with just a fuse and far harder to damage even when you get stuff wrong When you short stuff all that normally occurs is blowing a fuse

I looked for every fuse I can lay my eyes on and even tested maybe 4 or five relays, all were good. After looking at some diagrams and searching online I couldn't find any mention of a fuse that specifically protects the ECU so naturally I thought my ECU burned out... I actually found it while I was replacing the old ECU with a new one I got from the dealer. I noticed a black little box with 4 more relays in it and saw two 15amp fuses on that box lol. The relief and happiness I felt when I noticed one of them was blown was quite intense
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Old Today, 03:29 AM   #10
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Default Re: Electrical issue after injector re-pin

Glad its fixed! I had a feeling it was something like this.
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