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Old 04-12-2008, 12:03 PM   #31
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Conversion Complete!

Last night I completed the CA to 49-state VX conversion. It took most of the night, but I was able to get it done in one aggressive evening. According to the lean burn monitor voltages it is working correctly. I'm getting the suggested voltage at startup, warm idle, and lean burn cruise.

Does anyone know what the estimated mileage is at roughly 65mph in learn burn mode? Is there any transfer function between the lean burn monitor voltage and miles per gallon?

The lean burn mode is surprisingly robust. I drove it a bit more today and found I was able to climb light hills at 70mph without it dropping out. It is also very quick to get into lean burn mode. I found I was able to get into it even on surface streets in fourth gear between lights if I was gentle on the throttle.

With two connectors and a couple extra connector pins I was able to do the install without cutting any of the OEM wiring. This allows me to easily regress to the original configuration if desired.

The wiring was an initial concern and then if I did get it wired correctly there was question about the used 5-wire sensor I had purchased. It was in good condition but I have heard of people having problems because they didn't know if it was the wiring or the sensor or the ECU for that matter.

Everything appears to be working well in my case and I just filled up the fuel tank so we'll see how the mileage is. I'll keep everyone posted if any problems should develop.

A DIY document is to follow. Thanks everyone for the support. Eco-tuners unite!

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Old 04-12-2008, 12:33 PM   #32
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Wandering, congratulations! That's excellent news.

I'm very interested in knowing how you did the wiring with just two connectors. I can see how to do it with four, but if there's a simpler way to do it I'd love to know what it is.

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Old 04-12-2008, 07:19 PM   #33
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I'm realizing that folks reading this thread might be confused by the fact that two different numbering systems are being used, to refer to pin (terminal) locations in connectors.

The connectors we're discussing are not physically marked with pin numbers. So one has to adopt a convention to refer to the pins by number. Trouble is, different conventions are being used.

When I refer to pin numbers in my posts here, I'm using the same convention used by Honda in their service manuals. That convention is expressed in this illustration. (By the way, in that illustration the term "locking device" is a reference to the device that clips the male and female connectors together. It is not a reference to the device that clips the female connector onto a mounting bracket.) Once you understand that illustration, you can follow the pin numbers that are used in schematics like this.

Other folks have posted comments (in this thread and elsewhere in this forum) which contain very helpful information, but which follow a different numbering convention, for some reason. An example of such a comment is here.

The convention implied in that post is that the locking device is facing to the left, instead of facing up. And that you are looking at the back of a male connector. Pin numbers in the Honda manuals follow the convention of the locking device facing up, and that you are looking at the front of a male connector (as expressed in the illustration I cited).

For example, that post indicates that the unused terminal (on the 49-state sensor) is pin 2. But the schematic I cited indicates that the unused terminal is pin 5 (it indicates that by omission). The point is that pin 2 and pin 5 are the same pin, depending on which way you hold the connector when you start counting pins.

This had me confused until I realized what was going on.
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Old 04-12-2008, 08:20 PM   #34
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Oh yeah, one more thing. Just to make things interesting, Honda uses a different numbering system (different from the two I've already described) with regard to the 3 plugs that attach to the ECU. The numbering system for those connectors is illustrated on page 11-25 of the service manual.

But that information is not essential to the conversion, because although you need to swap the ECU, there's no need to fuss with individual pins or wires down at the ECU.
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Old 04-12-2008, 09:28 PM   #35
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Wandering, I just figured out the answer to the question I asked you. I couldn't understand how you did the job with just two new connectors. Now I realize that you mentioned using extra connector pins. So I guess what you did is you altered C129. When your car came out of the factory, that connector had 3 blank positions (pins 2, 3 and 5). You filled in those blank positions with new connector pins. This gives you access to D8, D3 and D16 (respectively), which were wired (at the factory) to C211 on the shock tower.

I assume you wired your three new connector pins to a 3-wire shielded cable that runs to the vicinity of C111. At that end, you have the other two connectors I mentioned: an 8-pin female and a 4-pin male.

Your approach has the appealing simplicity of not needing those two extra connectors (the six-pin male and six-pin female which are required with my solution). I never thought of doing it that way because I don't know how to add pins to a Sumitomo connector. I think you need fresh pins and seals. I wonder where you got them from.

Maybe you got your hands on a kit like the one illustrated towards the bottom of this page. (By the way, that page illustrates yet another numbering system different from all the other ones that have been discussed so far.)

One advantage of my approach is it's easier to reverse the conversion without a trace. Your approach is very reversible, but your new harness stays in place (and with unmated connectors that are potentially subject to corrosion, unless you protect them somehow). But I think this is a very minor consideration.
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Old 04-13-2008, 03:51 PM   #36
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In Summary...

Good deduction! You are correct!!

Once you get your head around the wiring details the conversion is "fairly" straight forward.

You'll need the following Honda hardware:
49-state ECU
L1H1 5-wire O2 sensor

There are seven wires total that need to be accounted for. The break down I used was derived and simplified from the past table that was posted on the subject. See above.

Contained within the original CA O2 sensor connector are three wires that are utilized.

ECU A6 - O2 sensor pin 1 (orange)
ECU D22 - O2 sensor pin 5
ECU D14 - O2 sensor pin 6

To clarify as an example ECU A6 means pin 6 on the A connector of the ECU. Generally speaking A is the biggest, D is medium, and B is the smallest ECU connector. Pin 1 is in the top left with pin 2 directly below and pin 3 is one to the right of pin 1. See link for details:

On the O2 sensor connector pin 1 is similarly in the top left and for an OEM 5-wire L1H1 O2 sensor pin 1 is orange. The same pin numbering nomenclature is used on this connector as the ECU.

ECU D3 - O2 sensor pin 7
ECU D8 - O2 sensor pin 4
ECU D16 - O2 sensor pin 8

All three wires are in the bottom circular connector on the shock tower. On the half of the connector farthest from the firewall there are three rubber plugs in the pin holes and no wires coming out. The opposing side of the same connector closest to the firewall is fully populated with wires. There are the three required wires!

Disconnect the connector with the three rubber plugs. Pull out the three plugs with a small pair of pliers. Remove the white piece of plastic on the inside of the connector using the same pair of small pliers to gently slide it out. Now you have access to the pins. From the back of the connector slide in pigtailed connector pins from a donor connector that has been taken apart in a similar fashion. At this point three pieces of wire will be coming out of the reassembled connector. These will need to run from the shock tower to the O2 sensor connector.

Keep the plugs if you want to change back to the original configuration. Take the connector apart and remove the added pins then reinstall the plugs.

ECU A23 - O2 sensor pin 3

For the seventh and final wire I simply wired it to a chassis ground location. I checked continuity back to A23 on the ECU and it worked great.

I used two connectors to make an adapter from the factory CA 4-wire O2 connector to the 49-state 5-wire O2 connector. At this junction I spliced in the four wires including the ground to the proper locations going inbound to the O2 sensor connector pins from the shock tower. I connected the chassis ground to the shock tower.

Focus on connecting pin numbers on the ECU to pin numbers on the O2 sensor. The colors of wires between are different on different vehicles and for me it tended to complicate the process.

Before testing the car be sure to do multiple continuity checks from the ECU pins to the O2 sensor. The suggested wire mapping appears to be correct so be cautious if it doesn't check out with a multimeter.

I've tried to simply the conversion so please let me know if I left any important details out.
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Old 04-13-2008, 08:04 PM   #37
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Wandering, thanks for those very helpful details.

I'm going to summarize some key aspects of my approach, compared to your approach. There are some interesting similarities and differences.

As I mentioned before, I think readers should be warned that two conflicting numbering systems are being used. Consider the plug on the 5-wire sensor. If I hold that plug in my hand, facing the pins, and with the locking device facing up, I number those pins as follows:


Contrast this with the way you're numbering them (and some other folks here have also used this numbering system):


It's not a problem if a reader is aware and knows how to translate between the two. In other words, when I say pin 7, and you say pin 6, we're actually talking about the same pin. I'm counting left-to-right, whereas you're counting up-down.

Your system makes sense because it's the system Honda uses in numbering the ECU pins. Trouble is, they use a different system for their other connectors, like the various connectors we've been discussing. So you need to do it my way if you want to understand Honda schematics (like the one I cited a couple of times above).

Speaking of pin numbering, I want to warn readers about ECU pins. You referred to an illustration that numbers them as follows:


That's correct, provided you're facing a male connector (that is, the pins on the ECU itself). But someone testing continuity is facing the female connectors on the end of the cable. That means you're dealing with a mirror image, and the numbering needs to be reversed, like this:


Something else about pin numbering. Take a look at this schematic. The D portion of the ECU is connected to the main wiring harness via a connector called C404. The schematic indicates, for example, that ECU terminal D8 is connected to pin 15 on C404. When you think about it, you realize that Honda is numbering C404 as follows:

1 -2 -3 -4 -5 -6 -7 -8 -9 -10-11

Remember that C404 is female, so those numbers are interpreted with the connector facing away from you (as portrayed in this illustration). Notice how C404's pin 15 is in the position that corresponds with D8.

It's interesting to notice that the convention Honda uses for numbering ECU pins is not the same convention it uses for numbering pins on the connectors that attach to the ECU. On those connectors it used the same left-right (rather than up-down) system it uses throughout the vehicle.

I find it very helpful to use the Honda schematics, and I find that it helps to have a firm grasp of the pin-numbering conventions. So that's why I figure this is worth explaining.

Anyway, we've both made this important observation: all the wires needed to hook up the 5-wire sensor can be found under the hood. There's no need to run wires through the firewall to the ECU. Honda has already done that for us.

In particular, all the wires we need (aside from a ground) can be found in two places: the C111 connector (the 4-pin jack that served the original 4-wire sensor), and the C211/C129 connector. The latter is found on the passenger-side shock tower. On that tower, there is a mounting bracket that holds four sets of connectors. The connector pair at the very bottom (closest to the ground) is C211/C129.

C211 is the female side. It's part of the main wiring harness, and it has wires that run to the ECU. C129 is the male side. It's part of the engine wiring harness. These are 6-pin connectors. On a CA VX, three of the C129 pins are blank. These are the pins you and I both tap into (you do it by modifying the original connector; I do it by providing a new connector to replace the factory C129).

In both your solution and my solution, pin 4 (on the L1H1) reaches D3 (on the ECU) via pin 3 of C129 (I'm using my pin-numbering convention, not yours). And pin 6 (on the L1H1) reaches D8 (on the ECU) via pin 2 of C129. And pin 8 (on the L1H1) reaches D16 (on the ECU) via pin 5 of C129.

Similarly, in both your solution and my solution, pin 1 (on the L1H1) reaches A6 (on the ECU) via pin 1 of C111 (the jack that served the old O2 sensor). And pin 3 (on the L1H1) reaches D22 (on the ECU) via pin 2 of C111.

And in both your solution and my solution, pin 2 (on the L1H1) is connected to ground.

We take a slightly different approach to pin 7 (on the L1H1). We both connect it to D14 (on the ECU). You achieve this via pin 1 of C111. I achieve this via pin 6 of C129 (they amount to the same thing). In other words, you run 3 wires to C111, and 3 wires to C129, whereas I run 2 and 4.

Finally, you alter C129. What I do instead is use two extra connectors. This allows me to tap into the C211/C129 connector pair, without altering any existing wiring or connectors.

Why do I need two extra connectors, and not just one? Because the C211/C129 connector pair has a dual purpose. It doesn't just support the O2 sensor. It also supports the EGR valve. So my 4th connector is needed to maintain continuity to the EGR valve.

But that's a background issue that doesn't really need to be understood. I think my earlier instructions (for how to wire the 4 connectors) are accurate and sufficient. I'm more confident about that, now that I have confirmation from you that your C211/C129 connectors are wired to the ECU the same way mine are. I think we've both done a lot of continuity checking and come up with identical results. Also, what we've discovered is consistent with a bunch of different Honda schematics I've looked at (including, especially, the one I cited a few times).

One more thing. In the spirit of trying to reduce confusion, I want to mention that L1H1 has lots of names. Folks might not realize they mean basically the same thing:

5-wire O2 sensor
49-state sensor
wideband sensor
LAF (linear air/fuel) sensor
UEGO (universal exhaust gas oxygen) sensor
Honda part number 36531-P07-003
Bosch part number 13246 (which is a repackaging of NTK's L1H1, and which is not to be confused with the Bosch LSU4 series, which is also a wideband sensor but not interchangeable with L1H1)
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Old 04-16-2008, 12:47 AM   #38
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Hi Wandering and Monroe,
Where are you two located? I bought the parts to do the conversion last year Nov-Dec, but never got around to doing it. With gas hovering around $4/gal, I want to get going on this project.
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Old 04-16-2008, 12:53 AM   #39
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Originally Posted by Wandering Albatross View Post
Finding the 4-wire and 5-wire connectors at the junkyard proved harder than I thought.

Specifically I'm looking for a 4-wire from a bad O2 sensor and the 5-wire from the car's wiring harness. I need to dig up the 4-wire connector at a minimum.

Anyone have suggestions?
I went to two junkyards with no luck. I tried the big one in moss landing, no go. What additional connectors do I need? I just read the entire thread and am a bit confused as whether or not we need new connectors. I always thought I had to run wires into the car, but it seems like I don't.
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Old 04-16-2008, 05:50 AM   #40
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Hi Gary.

"Where are you two located?"

I'm in the Northeast. I think you're in CA. But I would be glad to try to help you remotely.

Will your car still be legal in CA, if you do the conversion? That's a question you would have to ask someone else. But my methodology is pretty reversible, so it would not be hard to cheat.

"I went to two junkyards with no luck."

I wonder exactly what you were looking for. There are different ways to approach the project, and they vary with regard to what new connectors are utilized. And the connectors might also vary with regard to how easy or hard they are to find.

Keep in mind it's also possible to do the job with no new connectors at all. If you were on a desert island with no source of parts, you could do the whole job with a sharp rock, and some electrical tape. (When I say "whole job," I mean the wiring tasks. You would obviously need other simple tools to physically install the ECU and the O2 sensor.)

In the sharp-rock scenario, you are cutting factory wires, and taking an approach that's relatively hard to reverse. With the proper connectors, you can create an installation that's easily reversible without a trace, and you can completely avoid cutting any factory wires or altering any factory connectors.

"I just read the entire thread and am a bit confused as whether or not we need new connectors."

There are very specific reasons why the discussion is confusing. For example, I've pointed out that different people use different pin-numbering conventions.

It would help me to know your level of electrical literacy. Do you understand how to read this schematic (especially the referenced pin numbers)? It would be possible to do the job without this schematic, by following the instructions I posted above (about how to build a custom harness). But this schematic is helpful, and it will be easier for me to guide you if I know how well you grasp the schematic.

As far as whether or not we need new connectors, you have a choice. I have described a method that uses 4 new connectors. Wandering used 2. And as I mentioned, the job could also be done with zero.

"I always thought I had to run wires into the car, but it seems like I don't."

That claim (that it was necessary to run wires into the car) has been made, but I think Wandering and I have both discovered that the claim is wrong.

Swapping ECUs is the only work you have to do in the interior of the car.

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