Civic VX Lean Burn Questions

[monroe74]

I'm new here. Please excuse me for barging in. Like Wandering, I have a CA VX that I want to convert to 49-state. Therefore I've been watching this thread with interest, and I appreciate the great info provided here by you and others.

soletek: "Wires you need to add: three wires that need to be shielded come from D3, D8 and D16. Yes, you have to run these wires all the way from the ECU."

Are you sure? Aren't those three (D3, D8 and D16) already present at C129? That's the impression I get from a schematic that was kindly posted by TomO (see here and here).

Maybe those wires are not present on your CRX (and therefore you had to run wires back to the ECU), but the schematic seems to indicate that they are present on every VX (and simply left unused on the CA version).

So I think all that's needed to wire the LAF (the new wideband 5-wire O2 sensor) is to create a special harness to run from the LAF to the shock tower. That is, from connector C111 to connector C129.

This would mean there is no cutting of any stock wiring, and no need to pass extra wires through the firewall.

Also, I think the needed harness could be ripped out of a junk VX (49-state). The tricky part is that it's bundled with a bunch of other wires. You'd have to remove the outer wrapping so you can leave behind the other wires and connectors you don't need.

Either that, or use the bundle (from the junk VX) as a complete assembly. This would create a result closer to a dead-stock 49-state VX, but it would require unplugging and replugging a bunch of connectors to other sensors. Not a huge deal, but it seems like a good idea to be able to switch back and forth between CA-mode and 49-state-mode. And that would be much easier if the old wiring bundle is left in place, and the new LAF connected with a separate harness.

[monroe74]

I had suggested the possibility of using the complete wiring assembly from a junk VX (49-state). I'm realizing that's not a great idea, since that complete wiring assembly is the engine wire harness, which comprises about 30 connectors. It's probably not worth messing with so many connectors just to create a dead-stock result. It makes more sense to rip out the C111-C129 portion of that harness (taken from a dead VX). Or to fabricate new wiring that amounts to the same thing, maybe using cannibalized connectors.

[soletek]

For those of you that don't know, the VX is a fairly rare junked vehicle. Good luck to those who wish to find junked Vxs in the wrecking yard. I'm not saying you can't, but there aren't any around here. As for the wires existing in the under-dash portion of the harness, none of the harnesses, without 5 wire LAF sensors, that I have used have ever had those wires. Why would Honda have the harnesses built with extra componentry, at extra cost if only one vehicle type and model would be using that setup. That would not be cost effective.

If you do find a VX harness, don't think you can only pick up the engine portion. You have to get the under-dash portion (or modify one yourselves as I did).

Monroe74, the easiest way for you to find out if your wires exist is to look in the pin locations in Connector D as noted above. If they are a different color, don't expect them to go to the same place. Use a multitester, or the like, to see if there is continuity from the ECU end of each wire to C129. As for the accuracy of Honda literature, the schematic on page 24-5 of the 1994 and 1995 Electrical Trouble Shooting Manuals from tomo's post display the wiring of both CA and Fed versions, four and five wire. In both cases the book is wrong in one aspect and that is that it shows all seven wires running all the way to the LAF sensor on the 5 wire, when only five wires enter the oxygen sensor out of the seven. In the 1993 Electrical Troubleshooting Manual (on page 24-2), only the five wire is referenced (because they had no four wire VX versions up to that date), and is also misleading with the same information. Only the 1992 Electrical Troubleshooting Manual (also, on page 24-2) shows the correct wiring schematic. D3 and the grn/wht wire never truly reach the LAF sensor, and loop at C111, pin 4 and pin 3 (loop not shown in the book).

One of the first things any Honda Master Tech will say regarding the books is that they have errors. I learned this the hard way. Good luck!

[monroe74]

sole: "the VX is a fairly rare junked vehicle"

Good point. I bet you're right.

"As for the wires existing in the under-dash portion of the harness, none of the harnesses, without 5 wire LAF sensors, that I have used have ever had those wires."

We're talking about what's called the main wire harness. My guess is that you were using harnesses from a model other than VX (like your CRX, for example). My belief is that the wires we're discussing are present in every VX harness (both CA and 49-state), but not in any other model.

Are you sure you ever ran into a CA VX harness that didn't have the wires?

"Why would Honda have the harnesses built with extra componentry, at extra cost if only one vehicle type and model would be using that setup. That would not be cost effective."

Good question. Here's an answer. We're talking about three wires that I think we agree are part of every 49-state VX. These wires are in the main wiring harness. On one end, they are found in connector C406, and connect to D3, D8 and D16 on the ECU. On the other end, they are found in connector C211, which is on the shock tower. From there, they ultimately connect (via the engine harness) to the 5-wire O2 sensor.

The question is whether these wires are also present in the main wiring harness of a CA VX (even though they have no use, in that model). I think they are. But why would Honda waste money including 3 wires that have no use? Because the CA VX was a small portion of overall VX production, and it would be a hassle to create a special main wiring harness just for the CA VX, with those wires deleted, just for the purpose of saving the cost of those three wires. It's simpler to leave them in, unused. Manufacturing is simplified any time a single part can be used in multiple models. Likewise for what happens down the road, when Honda is obliged to make replacement parts available on an ongoing basis.

Similarly, I think the rear wire harness on a VX has wires and connectors for a trunk light and rear wiper, even though those features were not offered on the VX.

"If you do find a VX harness, don't think you can only pick up the engine portion. You have to get the under-dash portion"

That's true, if someone is trying to put a VX engine into a non-VX body (like you did with your CRX). But I think you don't have to worry about the under-dash portion (the main wiring harness) if you already have a VX. And that's the situation Wandering and I are in.

"Use a multitester, or the like, to see if there is continuity from the ECU end of each wire to C129."

I agree with you that it's a good idea to verify that the wires go where I think they go.

"In both cases the book is wrong in one aspect and that is that it shows all seven wires running all the way to the LAF sensor on the 5 wire, when only five wires enter the oxygen sensor out of the seven."

I understand your point. I agree that the drawing is confusing, but it makes sense once you realize that the calibrating resistor is housed in the C111 connector itself, rather than in the body of the O2 sensor.

"they [the books] have errors"

I'm sure they do. But likewise for comments people write on forums like this! Anyway, I intend to take your advice and verify (with some kind of continuity tester like a multimeter) that the wires I see on the shock tower (at C211/C129) actually go where I think they go.

[Wandering Albatross]

Thanks for the numerous pieces of useful information. I think I have a pretty fairly good idea of how the conversion is performed. If I can pull it off I plan to put together a DIY. I'm going to give it a go this weekend.

As questions arise support would be appreciated!

[soletek]

Originally Posted by Wandering Albatross

As questions arise support would be appreciated!

I'd be very happy to help you. Just send a PM anytime.

[monroe74]

I think I've made some progress in figuring out the wiring (as far as converting my CA VX to 49-state). I haven't fully installed and tested this yet, but I've done a bunch of tracing and continuity testing, so I think it will work. But hopefully someone can tell me if it looks like I've made any glaring errors.

My goal is connect the new parts (ECU and O2 sensor) without cutting any existing wiring. I want to do it all via standard Honda connectors, so the installation will be easily reversible, without a trace.

Three ECU terminals (D3, D8 and D16) are used in the 49-state VX, but not in the CA VX. The good news is that the CA VX already has the needed wires in place in the main harness (at least this is true in my '95 CA VX; I verified this with a continuity test). This means if I create a custom harness, using 4 connectors, I can install the new O2 sensor without cutting any wires.

I was able to find the needed connectors at a junkyard. I didn't need to find a VX; the needed connectors are used in a bunch of different places on the other '92-'95 Civics. The needed connectors are as follows:

8-pin female
6-pin male
6-pin female
4-pin male

You create your custom harness by wiring them together as follows:

8-pin female.
pin 1 needs to be wired to 4-pin male, pin 4.
pin 2 needs to be wired to ground, G101.
pin 3 needs to be wired to 4-pin male, pin 2.
pin 4 needs to be wired to 6-pin male, pin 3.
pin 5 is not used.
pin 6 needs to be wired to 6-pin male, pin 2.
pin 7 needs to be wired to 6-pin male, pin 6.
pin 8 needs to be wired to 6-pin male, pin 5.
The wires from 4, 6, 7, and 8 need to be shielded, and the shield should be grounded.

6-pin male.
pins 2, 3, 5 and 6 are referenced above.
pin 1 needs to be wired to 6-pin female, pin 1.
pin 4 needs to be wired to 6-pin female, pin 4.

6-pin female.
pins 1 and 4 are referenced above. pins 2, 3, 5 and 6 are not used.

4-pin male.
pins 2 and 4 are referenced above. pins 1 and 3 are not used.

That's a total of eight connections that have to be made, to join these 4 connectors together to form your custom harness. (There's one more connection, a ground, that will be made when you're installing the harness on the car.)

The harness is installed on the car as follows:

8-pin female. Connects to new O2 sensor, C111.
6-pin male. Connects on shock tower, to female of C129.
6-pin female. Connects to male of old C129.
4-pin male. Connects to old C111 4-pin female (the connector your old O2 sensor was plugged into).

The following is reference information. It's stuff you don't really need to know. It's the wiring instructions, with extra information that could be useful if you want to know more about what's really going on. Or if you need to trace things for troubleshooting purposes.

8-pin female.
pin 1 needs to be wired to 4-pin male, pin 4. This line goes via C103, pin 2, and ultimately reaches A6.
pin 2 needs to be wired to ground, G101.
pin 3 needs to be wired to 4-pin male, pin 2. This line goes via C103, pin 9, and ultimately reaches D22. A6 and D22 were in use in connection with the old O2 sensor, so we're taking advantage of the existing plug and wiring.
pin 4 needs to be wired to 6-pin male, pin 3. This line goes via C129, pin 3, and ultimately reaches D3. The old O2 sensor did not use D3. But we're taking advantage of the fact that C129 already is connected to D3, even in a CA VX.
pin 5 is not used.
pin 6 needs to be wired to 6-pin male, pin 2. This line goes via C129, pin 2, and ultimately reaches D8. The old O2 sensor did not use D8. But we're taking advantage of the fact that C129 already is connected to D8, even in a CA VX.
pin 7 needs to be wired to 6-pin male, pin 6. This line goes via C129, pin 6, and ultimately reaches D14. The old O2 sensor did use D14. So we're reaching D14 via C129, pin 6, just like the old O2 sensor did.
pin 8 needs to be wired to 6-pin male, pin 5.This line goes via C129, pin 5, and ultimately reaches D16. The old O2 sensor did not use D16. But we're taking advantage of the fact that C129 already is connected to D16, even in a CA VX.

6-pin male.
pins 2, 3, 5 and 6 are referenced above. Those pins connect the O2 sensor to the ECU.
pin 1 needs to be wired to 6-pin female, pin 1.
pin 4 needs to be wired to 6-pin female, pin 4.
Pins 1 and 4 connect the EGR to the ECU. See below.

6-pin female.
pins 1 and 4 are referenced above. pins 2, 3, 5 and 6 are not used.
This connector, with those two connections, is needed to take care of C130, the EGR valve. It's wired via C129. Since we're interfering with C129, we're essentially providing a jumper so the EGR is connected exactly as before.

4-pin male.
pins 2 and 4 are referenced above. pins 1 and 3 are not used.
This connector allows the new O2 sensor to reach A6 and D22 in exactly the same manner that the old one did.

[monroe74]

A few minor corrections/clarifications with regard to my terminology.

I said the new 8-pin female connector (in the custom harness) "connects to new O2 sensor, C111." That's basically correct, except that I should be more careful with the way I use the term "C111." I was implying that C111 is the male connecter that's wired to the O2 sensor. It's not. C111 refers to the female connector that mates with the male connector that's wired to the O2 sensor.

Also, as you look at various drawings it might be helpful to keep in mind that C111 can be either a 4-pin female connector or an 8-pin female connector. It's the former in CA and the latter in the other 49 states.

I made a similar mistake when I said this: "6-pin male. Connects on shock tower, to female of C129." Actually, "C129" is the name of the 6-pin male. The female counterpart (mounted on the passenger-side shock tower) is called C211.

I made a similar mistake when I said this: "6-pin female. Connects to male of old C129." I should have said "connects to old C129, which is a 6-pin male connector."

In other words, the new custom wiring harness has a new C129 and a new C211. The former attaches to the old C211 and the latter attaches to the old C129. You can think of these two new connectors as being a jumper between the two old connectors.

The other two connectors on the new custom wiring harness (the 8-pin female and the 4-pin male) act in a similar manner. You can think of them as a jumper between the new O2 sensor and the old C111 that the old O2 sensor used to be connected to.

Another minor correction. I said this: "we're taking advantage of the fact that C129 already is connected to D3, even in a CA VX." It would have been clearer and more correct to say "C211," not "C129." The latter is a male which plugs into the former.

I do the same thing in a few other places (refer to C129 when it would have been more correct to say C211).

[Wandering Albatross]

Monroe74, it sound like you are making lots of progress.

I quickly read over your spiel and I'm a little unclear how you are interfacing with the new 5-wire O2 sensor. I saw that you purchased a 4-wire connector from the junkyard (like the one on the CA O2 sensor) but I didn't see any mention of the 5-wire connector that is normally on a 49-state car's wiring harness. This would be used to interface to the 49-state O2 sensor.

That said I don't have all of the connector CXXX's memorized so it could be in there. From what I gather you can't cut the connector off the 5-wire O2 sensor because the calibration resistor is physically inside the connector housing. With the 5-wire connector I had a difficult time finding it and ended up purchased it from the mentioned eBay user in a earlier post in this thread. I had no luck at the junkyard with that particular connector.

[monroe74]

"it sound like you are making lots of progress"

Thanks for your kind words. I started out by finding lots of helpful information in posts by you and others, here and elsewhere. It was nice to not have to start from scratch.

"I saw that you purchased a 4-wire connector from the junkyard (like the one on the CA O2 sensor)"

Yes. To build the custom harness, I grabbed 4 connectors from a junkyard. One of the 4 connectors is a 4-pin male, and it is identical to the connector that is wired to the CA O2 sensor that was put on my car in the factory.

I need this 4-pin male so I can connect my custom harness to the 4-pin female (C111) that used to connect to the old O2 sensor. This 4-pin female has value because it gives me a way to reach A6 and D22.

"I didn't see any mention of the 5-wire connector that is normally on a 49-state car's wiring harness. This would be used to interface to the 49-state O2 sensor."

There is no 5-wire connector that is relevant to this discussion. The 49-state sensor does not have an 5-pin plug. It has an 8-pin plug. Those 8 pins are accounted for as follows. 5 pins are connected to visible wires that travel to the sensor housing (that's why it's commonly described as a "5-wire" sensor). Two of the pins are attached to a resistor that is hidden inside the male connector itself. One pin is unused.

"I don't have all of the connector CXXX's memorized so it could be in there."

It's easy to get confused. I recommend this schematic, to help you picture what's going on. I also recommend not paying too much attention to colors. Instead pay attention to the pin numbers in each connector, and then you can visualize the path between the O2 sensor and the ECU.

But I think my post above has all the information needed to do the wiring, and understanding the reasoning and the details is optional.

There are aren't that many connectors that you need to know about. Consider the CA car before we start changing things. There's a 4-pin male wired to the O2 sensor. This plugs into a 4-pin female, C111. C111 is part of the engine wiring harness. Those 4 wires from C111 go to various places, but what's most relevant is that one wire goes to C129. This is a 6-pin male, which plugs into C211. C211/C129 are on the passenger-side strut tower. C211 is part of the main wiring harness. It has 4 lines that run to the ECU. A CA car uses only one of those lines. A 49-state car uses all four.

To install the custom harness I described, you need to unplug C129 from C211. Then the 4 connectors on the custom harness attach to C129, C211, C111, and the new O2 sensor. And there's a ground connection, for the shielding. That's it.

Aside from swapping the ECU, these are the only connectors you have to mess with. And there is no need to cut any stock wiring, and no need to run new wires through the firewall to the ECU.

"From what I gather you can't cut the connector off the 5-wire O2 sensor because the calibration resistor is physically inside the connector housing."

Yes, there is a resistor hidden inside that particular connector. But I have no idea why you would have an interest in separating that connector from the sensor. I don't see what you're trying to accomplish by doing so.

"With the 5-wire connector I had a difficult time finding it and ended up purchased it from the mentioned eBay user in a earlier post in this thread. I had no luck at the junkyard with that particular connector."

As I said, it's not a 5-pin connector (wired to the 5-wire sensor). I don't see how a 5-pin connector is going to be of any use to you. It's an 8-pin connector. And to work with the 49-state O2 sensor, you definitely need an 8-pin female connector, to accept the 8-pin male that is wired to the sensor.

This 8-pin female that you need is not hard to find. For example, C125 will do the job (see page 23-17 of the service manual). I think C125 is present on every '92-'95 Civic. And I think the connector will most likely be there even if the engine has been ripped out. And it's in a spot that's easy to reach.

The other three connectors needed to build the harness are similarly easy to harvest.