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I recently purchased a OBD1 JDM P72. I thought the ecu was unchipped, but when I had a peak inside, there was a 28 pin socket w/rom, and the 373 chip. J1 had been jumpered also. So I do a little reading through this forum, and I find out about this whole IAB thing. From what I've read the IAB pin on the JDM ECU is 17 not 19. My conversion harness has the OBD2 pin A26 going to pin 19 on the OBD1 side of the harness. This was my first concern, but I decided to see if the IAB's would work the way it was wired. So, I hook up the JDM P72, and I immediately get a code 13. From what I read this is the PA sensor, which I believe is internal on the P5 ECU. I do a little more reading and decided that I would try and run the factory JDM rom. So, I pull J1 off and start the car. Now I get a code 9. I'm a bit confused because my OBD2 P5 wasn't throwing any of these codes. The only code that my P5 would throw was a P0420 for a faulty catalytic converter, which my high flow cat is old and, deteriorating. And this code would only throw after 3 consecutive driving cycles. Does anyone have a clue why this JDM P72 is throwing these codes? Did I get a piece of junk?

I also tried an unchipped JDM P30 yesterday, and I recieved the same code 9 CEL as the onboard JDM P72. Does anyone have a clue why these ECU are throwing a CYP sensor code? I will be extracting the bin file from the JDM P72 external rom, so maybe someone can tell me something about this file.

The CYP sensor is probably wired differently in that harness. Check where the wires are supposed to go and make sure they do.

I am getting the exact same thing, I tried 4 different ecus and 2 diferent harnesses, I got #9 every time. Here is my post viewtopic.php?t=9713 We need to look into it, I will be trying some things tommorow, I will keep you guys posted.

Here's what I was told from one of the best tuners on the east coast!

"If in fact your JDM p72 is socketed and has an eeprom chip in it it's more than likely that they didn't disable ELD, injector test circuit, and baro pressure sensor. These three things will throw codes if you put a USDM based bin file in a JDM ecu since the ecu does not have these onboard."

Also here is the original bin file from the chip, and the second is one is modified by disabling the above sensors.

Yes, you were told correctly. I have a jdm PR3 and I always disable baro and injector test when I run it. The problem that we both see has nothing to do with it. I tried different ecus, jdm and usdm and they all threw #9 cel. I am just guessing at the moment but I think it may have something to do with phasing of the cyp pulses as compared to the tdc and ckp sensors. I will look into this as soon as I can, I was planning to do it today but it looks like I won't be able to.

I looked at your bins, the one you pulled of the the original chip looks like a stock 273 bin. The other one, you modified, looks like a stock 273 with a raised rev limit to 8522, and disabled sensors. You don't have to disable knock since p72 has a knock board and you don't have to select the speed limiter (unless you want to). You may also change the name of that bin because I see someone taking it and trying to run their h22 with it since it has h22 in the name

I have to disable my knock sensor because my block is bored .080" over. 87mm to 89mm the stock knock sensor is designed around 87mm diameter. My knock sensor throws a CEL when not disabled. I actually have to trick the OBD2 P5 in order to stop it from throwing a CEL.

Well I will be trying the modified code later today after i get off of work.

Does anyone have the pinouts for the OBD 1 JDM P72 ECU? From what I understand the USDM IAB's are pin 19 and the JDM P72 is Pin 17. I'm wondering if there are other pin differences? How the heck do you get the pins out of these conversion harnesses?

Well I tried the different bin file, and the car threw the code 9 CEL. This thing is really ticking me off.

From what I understand about the JDM ecu is that A17 is +12v and it can be bridged to A19 for a EDM car to make the IAB's work because the EDM A19 is also +12v, but the USDM is -12v at A19. I am using a JDM P72 in a UK car and know that my IAB's are working using the bridging method but I don't know how you get around this in a US car.

After looking through my helms I've developed this hypothesis. The conversion harness must not be running the cyp signal to the right pins.

Using the data which preludedude has provided with the USDM ECU's also throwing the code 9 CEL. I have to believe that the pins on our conversion harness are wrong. The OBD2 Ecu's work perfectly fine, but any other OBD1 ECU throws a code 9 CEL. Now I've only tried JDM ECU's thus far, but prelude dude said that he has tried USDM ECU's with the same result.

There has to be others that have gone from OBD2 with a H22 to OBD1. I know people have done it without problems, so in my mind it has to be the harness.

I tried two harnesses and I got the same cel. I already looked into the harness, the only thing I want to try is to reverse the wires. I make my own harnesses and here is the pinout for the cyp sesnor

OBD2 OBD1
C4 CYPP B11 CYPP
C14 CYPM B12 CYPM

Look at the attached Helm's diagrams. I attached OBD2 Integra diagram because I have a printed version of the Prelude Helms Manual and I would have to scan it. The OBD2 CYP pinout for Prelude and Integra is the same.

I was looking at those same schematics in my helms for the lude. I am wondering if the TDC, and CKP sensor are playing apart in the code 9.

I swaped the cyl wires around and still got the code. I know my harnesses are good because I used them on whole bunch on obd2 civics with B16 swaps.