I decided to try and tackle making a OBDII to OBDI harness.
I have a spare OBDII ECU which I can use the plug from and can get some OBDI harness plugs for pretty cheap.

Ive never tried this before so I need some help.

First of all..how do I go about removing the gray "plug" from the ECU board? It has to be desoldered? What do I use?

Thanks.

 

up

 

No one that knows how to do this will help you. They lose money by giving away free information. Sorry to break it to you.

 

Its alright...I can figure it out myself..and I WILL share it with everyone.

I worked on it some last night. I removed the gray plug from the ECU circuit board using an air compressor and a grinding tool. I ground down the three soldered screws and also ground down the pins that are soldered throigh the board.
Took about 2 minutes and take off perfect.
Ill try to provide a picture.

Next I will be getting OBDI wiring harness-to-ECU plugs and start the soldering.

 

this is excellent, good luck.

 

sure man..
get some pics
i would like to see how you do that

good job

 

Heres the picture...



The pins on the left are how they were soldered to the board (bent) while the pins on the right I have straightened out...ready to solder wire to them.

You can see on the circuit board where I ground it down to "release" the pins.

 

save yourself the trouble and buy a harness from kenji.

 

...and spend the extra $200 which I cOuld spend on something else? WHY?

 

and spend the extra $200 which I cOuld spend on something else? WHY?


Well put I agree...Plus it will be quite the experiment and if it works, great.

 

very cool!
i have been thinking about doing this too. i just didnt know where to start. i hope it goes well for!

 

Hey HX,
Here's some hints that might help you with effort, and saving the motherboard
should you decide to reuse it,

Go to radio-shack and buy a soldering iron, and a solder-sucker.
heat the solder around the pins, and suck the solder up, the pins will
slide out nice and clean, and no damage to the ECU board (I used to assemble electronics all g0d-damned day...fun fun fun)

If you need anymore help, let me know

PEAYYYYACE!

 

I have made a list of what each OBDII pinout equals which OBDI pinout

OBDII Connector D

1 TPS = D11
2 ECT = D13
3 MAP = D17
4 VCC1 = D19
5 BKSW = D2
7 PHO2S = D14
8 IAT = D15
10 VCC2 = D20
11 SG2 = D22
12 SG1 = D21
13 SHO2/SG = NA
14 SHO2S = NA
16 EL = D10

OBDII Connector C

1 CKFP = NA
2 CKPP = B15
3 TDCP = B13
4 CYPP = B11
5 ACS = B5
6 STS = B9
7 SCS = D4
8 K-LINE =
10 VBU = D1
11 CKFM = NA
12 CKPM = B16
13 TDCM = B14
14 CYPM = B12
16 PSP SW = B8
7 ALTF = D9
18 VSS = B10

OBDII Connector A

1 INJ4 = A2
2 INJ3 = A5
3 INJ2 = A3
4 INJ1 = A1
5 SO2S HTC = NA
6 PO2S HTC = A6
9 LG1 = A26
10 PG1 = A23
11 IGP1 = A25
12 IACV = A9
15 PCS = A20
16 FLR = A7
17 ACC = A15
18 MIL = A13
19 ALTC = A16
20 ICM = A21
22 LG2 = B2
23 PG2 = A24
24 IGP2 = B1
27 FANC = A12

The only one I dont have a mathc for is OBDII C8.
It stands for "K-LINE" and "sends and receives scan tool signal.
Is this teh same pinout as OBDI D7 "TCD/RXD"? OBDI D7 is the only pinout I have left unaccounted for on the OBDI diagram. OBDI D7 wire goes to the "Data Link Connector"

 

just wanted to say, good luck! and if you can, document this as well as you can. you'd be helping countless other people.

 

Nice job so far buddy

Good luck, and keep us informed

 

I did find out that OBDII C8 = OBDI D7.

Im all good to go them. I purchased some "electrical" solder and will begin assembling the conversion harness a little later today.
My chipped OBDI ECU is also ready for pick up...so it should all be in tonight...maybe ready for the track...and possible with some luck...13s!!!

 

out of curiosity, what method are you using to figure out which connections match up?

 

Its actually pretty simple.

Im just cross referencing an OBDII Helms manual wit ha OBDI Helms manual.
The Helms shows a picture of the ECU plugs and what each pin/wire goes to.
All the pinouts in the Helms are labeled...then I go find the same label in the other manual.

Pretty easy huh? Just a little time consuming.

 

Finished the harness yesterday actually. Took me about 4 hours.
Plugged it in..started it up..and worked! From the first try...no codes or anything

It was real easy to do...just time consuming. I might do a write up on it if I have time..Ill see.

Oh yes...the OBDI ECU with higher rev limit is in..and already dyno tested this morning...results will be posted soon

 

nice.. man..
yeah post your work when you have time..
you are so awesome

 

Awsome....I have been waiting for my ECU for over 2 weeks now, cuz honda is waiting for a shipment of 20 OBD2 to OBD1 convertors....I should have made my own!

 

What? OBD2 to OBD1 convertors from Honda?
you should about that man..
how much is that? .. and why in the blue hell does Honda shiping this kinda thing into North America?
Let me knwo man.. coz i might want to get one as well.. ^^

 

you know, there s a metod of removing solder without destroying the board with a grinder
you can buy one at radio shack for a few bucks

it's a plunger that sucks out the solder after you heat it up

 

Yea but why waste the time/money of doing it that way?

The board is useless after you remove the ECU plug...so why save it?
Grinding it down takes only a minute to do.

 

The solder sucker/remover that Radio Shack sells for a few bucks will NOT, I repeat, will NOT desolder the pins that go into the printed circuit board. It may be able to do it after quite a few tries. Trust me on this one.

If any of you are interested in purchasing an OBD2 to OBD1 ECU conversion harness please email me at kenji211@gte.net I can do just about any conversion from 1988 to 2001. This means OBD2 to OBD1, OBD1 to OBD2, OBD2v2 to OBD2v1, EF to OBD1, EF to OBD2, etc.

I even offer VAFC harnesses to allow you to wire up a VAFC without cutting any wires. This will help to save your warranty.

Sure, you can make your own but after you buy the OBD1 ECU plugs and the OBD2 ECU and cut it up you are into it for quite a few bucks. Then comes the fun part...soldering the thing together. After you invest that time in the assembly and the money on the parts chances are you are into it for well over what I charge. I don't know about you guys but my time is VERY valuable.

The choice is yours. Either way I wish you all the best. Drive safely.

-kenji