Kill switch electrical questions
 

Disclaimer: I am not an electrician! Which is why I'm having trouble figuring out just how to go about installing a fuel injector kill switch on a 7th gen Civic. First, the schematic:

http://i1047.photobucket.com/albums/...hschematic.jpg

Unlike the 5th and 6th gen cars, it seems my 2005 has two FI relays (each marked "main," confusingly)--Relay 2 grounds through the fuel pump, and Relay 1 through the ECM? So, do I have to cut both of them or just one? Would cutting the ground from Relay 2 cause fuel pump issues when trying to start the car again? Would cutting the ground on just one relay even shut down all the injectors in the first place?

IMHO, don't cut power to the fuel pump. Cut power to the common hot wire to the fuel injectors.

what i would want to do is find the yellow/blk wire just before it splits off to the 4 injectors and wire in a switch/relay at that point

Ha--I was so focused on the relay ground, that didn't even cross my mind! Thanks!

I found the yellow + black wire at a 9-pin connector near the driver's side hood hinge. I think maybe only 8 wires there, but it's a 3x3 layout. That connector might still be there on your Gen 7, mine is Gen 6.

Other people have tapped into the computer's connectors. I'm just not comfortable working on those connectors with dozens of tiny pins and wires. But I know it's been done successfully.

Here's how I wired mine, thread. The principle's the same for your Honda, cutting your yellow/black wire.

for the understanding of the wiring:

both relais are grounded through the ecu. the fuel pump gets power over relais 2. relais 2 is switched by relais 1 and ecu. don´t be confused, by the upside down relais 2.

so, if u have troubble to find the injector wires, u can also cut the wire from relais 1 (coil) to the ecu.

I cut the ground for my PGM-FI relay and that also shuts down the fuel pump. I have been driving like this for almost a year, heavily using the switch. No fuel pump issues. Fuel pressure remains fine, because pressure just does not leak from the line in seconds (barring a leak). CAUTIONS: I am also not an electrician, and therefore want to warn you not to rely just on this FI wiring diagram when deciding where to cut a wire. Consult other wiring diagrams too. When I was installing my alt kill switch, the alt wiring diagram showed me what seemed a good place to cut, but it was not revealing that where I planned to cut would also disable an O2 sensor. Do this slowly, and do your mod reversibly first, so you can test effects of changes and avoid troubles. Lastly, the advantage of cutting the ground to the PGM-FI is that there will be no live power running through your switch. I get a nice clean cutoff too. I hope that info is helpful.

Based on the above diagram with what is visible, I would cut the ecm wire or red/yel wire, this will have the least amount of current of any of the lines and will cut off the ecu along with the fuel pump/injectors/ign, ect. If I could see the rest of the wiring, that may change but I doubt it.

Cutting the FP only will allow fuel to trickle through the injectors under low manifold pressure. Some cars will even run without the FP being on if they are of the centrifugal type.

Just look for the injector ground and cut that

Then you'll have a cel

the only red/yellow wires i see are the relay 1 control, and the purge valve control

each injector is individually grounded by the ecm

Relay 2 is operated by Relay 1, interrupt signal to relay 1 and you cut everything. You'll probably get a CEL when you interrupt the circuit which will kill ecu and FP, but when the circuit is closed it should reactivate with no CEL and nothing stored in the memory. Unless your generation has some queer test routine in the ecu it should work. I do all of my cars this way, even use it for an anti theft.

It works! I cut the red/yellow wire between the ECM and first relay, and (at least sitting in the driveway) it works perfectly. Engine shuts down, MIL comes on, battery and oil lights don't, everything else stays functioning.

http://i1047.photobucket.com/albums/...720_134131.jpg

Oops--seems I spoke too soon. The kill switch is tripping the immobilizer system, so I have to key off anyway to reset it. Looks like I'll have to hunt down the injector power wire under the hood after all.

Well you'll figure it out... until then, at least you have a nice looking switch. :)

Sorry that didn't work out, but thanks for reminding me to never buy a post 2000 car.

Trying to figure this out for my '01 HX.

Did you ever figure out a good solution? Did you interupt the Yellow/Black wire to the injectors similar to SentraSE-R?

and looks like Honda's schematics don't agree with you!

Eh?

Did you look at the schematic? Yel/Blk positive to each injector from PGM-FI Main Relay 1, negative color varies by injector and goes directly to ECM/PCM. How does it not agree?

Mine is an '01, here is a more detailed Wiring Diagram. It's drawn differently, but has the same grounds going to the ECM/PCM and yel/blk positive feeding the injectors.

Sorry, thought that was the grounds that came together as one, not the live wire! Apparently I read the schematics backward!

No, I haven't had time to revisit this. I've been using the switch and turning the key off then back on before I bump start it to reset the immobilizer. You'll have to insert the switch before the yellow/black wire splits to the injectors but after it splits off from the wire that goes to the immobilizer. If you hunt for it before I get around to it, post up!

I know its been awhile, but has anyone had luck with getting this to work? I'm considering doing it to my 02 civic soon.

Well, I currently have all the electrical bits I need (wires, relay, switch, etc) and I know about where the wire is that I want to find (Yellow/Black wire behind glove box). I pulled off the glove box door...

And found out it's going to take some digging. It's probably mounted to the firewall, but the HVAC system and the ECM are in the way. And, since the ECM is right there, there are a ton of wires in the area, including some for the air bag system which I really don't want to mess with (Any time you mess with the SRS system in these Hondas, there is a non-trivial reset procedure you have to go through to get it functional again).

Needless to say, I haven't tackled it yet. I'm considering trying to find the wire under the hood instead, since it travels from under the dash to the fuel injector harness on the engine.

Also, it's my daily driver and I'm in the middle of redoing the flooring in my living room and kitchen, so I've had no time to work on it.

VMan, did you make any progress?

I accessed the injector power lead at a large connector (my Civic is '97, Gen 6) near drivers side hood hinge. Aside from having to snake a wire through an existing rubber boot in the firewall, the job was not too difficult. I definitely don't relish the thought of working through stuff behind the glove box.

Here's the post.
http://ecomodder.com/forum/showthrea...tml#post175914
Go to the first post in thread to see photo of the connector.
The link above tells which wire it is - it's not the fat one easily visible in photo.

If you're not handy with relays like I am, there's nothing wrong with using a simple switch on the dash, as long as you have good solid connections at every point along the way. Probably should use a wire just a bit thicker than what you cut into, because you're adding length to the run. My switch is a toggle and I like it. Flip it off to kill, flip it on again right after engine dies to re-enable fuel injection. That way when you bump it to start, it will catch. If you use a momentary disconnect instead, then you need to hold it down till the engine dies. That's less convenient, imho.

I have some bad guys.

I traced the yellow/black wires from the injectors. They all meet up in a single connector next to the ignition coils. They don't meet before the connector like we were hoping. I took apart the connector and all the wires are connected to one another.

Right now the only option I see is to set up relays for all four of the wires. I really don't want to have to do this if I can avoid it.

I'm currently looking into using two DP relays or an industrial style relay with four poles.

If anyone can come up with a better solution let me know. Otherwise I will continue forward on this.



https://imageshack.us/scaled/large/17/dscn3087rb.jpg


https://imageshack.us/scaled/large/163/dscn3088l.jpg

That is exactly what you were supposed to find. The top y/blk one in this connector is the common feed wire for the 7 others. That is the wire you want to put on the switch. This image shows it is the one next to the w/blk wires in the connector.

Thanks. I did not have that wiring schematic in my Chilton manual. Could you possibly post the whole page so I can check where the others go?

I want to make sure that one of those doesn't connect to the immobilizer circuit(which is the problem we have been having all along).

I feel that the one common yellow/black is the same as the one at the fuel relays behind the blower/ecu in the cab, which if I'm correct connect to the immobilizer as well.

Also I'm sorry for the ambiguity in my last post. When I checked it, it appeared that all the wires are connected. Not just the wires to the fuel injectors.

Here you go.

i know its not related to this thread but i see you have a exaust insulation, did you see any difference with that?

The exhaust wrap has been on there for about 7 years, long before I got into ecomodding. So unfortunately I don't have any before after MPG numbers.

Here's the link again to the complete wiring diagram:
Wiring Diagram

The common yellow/black is for injectors, IAC valve, and CKP and TDC sensors. All of these are on the engine itself, and I would guess that killing the whole lot won't trigger a CEL or the immobilizer. This is the wire I plan to interrupt with my kill switch. Tracking down where it goes would be helpful.

I mostly haven't gotten around to it because I'm replacing the rag top on the wife's Mustang (harder than it looks...) and that's using up all my garage time.

Thanks everyone. It does look like the common yellow/black is the way to go.

The only concern I have is with the crank position sensor. I know the engine can run with just the crank position sensor or the cam position sensor working, but I think it might put it in limp mode.

Ain't gonna be running at all with the power off to the injectors.

Well, now that the Mustang is done, I did a little more wire tracing last night.

http://ecomodder.com/forum/member-da...ingdiagram.png

Highlighted orange is the yel/blk wires I am trying to follow, highlighted green is the wire I want to interrupt.


http://ecomodder.com/forum/member-da...6-19wiring.png

In my hand are three relays. The brown one is PGM-FI Main Relay 1, the blue one is PGM-FI Main Relay 2, not sure what the other one is. One yel/blk from each relay goes up and connects with two more yel/blk (this junction is just to the left of the PCM and is wrapped in blue shrink tube). One of those yel/blk goes to the immobilizer (left of the picture) the other is supposed to go to C102. The wire that is supposed to go to C102 is flagged with some electrical tape.

Which brings me to where I am stuck at. The gray, 20-pin connector (looks white in the pic) just right of my wire marked with tape... is this C102? I can only find two yel/blk wires, my marked wire and one that appears to go under the hood (but this one is far more difficult to follow). According to the diagram, there should be two more going to IGP1 and IGP2 on the PCM. I can't find these. The wiring diagram has the caveat of "except GX & HX" and it's possible my HX doesn't have these wires. I'm concerned that if I interrupt my flagged wire, I may also interrupt the IGP1 and IGP2 to the PCM which may trigger a trouble code or something.

Any thoughts?

the green marked wire feeds the injectors? why dont u cut the red yellow at main relay 1? in my eyes, this will bring down the whole system without trouble and with little current.

The highlighted green wire is for the injectors, crank sensor, TDC sensor, and IAC valve. Kill it and the engine dies, hopefully with no codes generated.

Cutting the red/yellow wire would kill the immobilizer and I would have to key-off/key-on to restart the car.

I'm not sure of the function of the IGP1 and IGP2 at the PCM. If killing this wire to the PCM triggers a trouble code, it could cause problems as well.

C102 is ground? sure?? and the fuses are ground too?

did u test the relais 1 and and the immo issue? maybe by pullig the relais?
what is the key doing, to reset the immo?

Sorry, I was incorrect earlier. The injectors are each controlled by a switched ground; I would be interrupting the common power wire going to them.

C102 is a junction/connector in the harness. There are a large number of wires going to it (at least 13 per the wiring diagram).


I haven't tested killing Relay 1...
But Vman455 did. See post 14 and 15 of this thread. Since it didn't work for him, I didn't bother trying it myself. I haven't delved into precisely how the immobilizer works, I just plan to avoid touching any wires related to it.

Well, I went ahead and did it last night. I snipped the yellow/black wire on the backside of the connector shown in the picture above. I wired up a relay and tested it on the way into work this morning.

Flip it off and the engine cuts out immediately and the MIL comes on. No Immobilizer light on the dash. Flip it back on and I can bump start it right back up any time.

The only unexpected behavior is that my Ultragauge turns off when I flip the switch.