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195 Posts
Discussion Starter · #1 ·
So I have a 98 spec low comp jdm b20b with a p75 head in my 98 integra ls. All stock. Only mod is an obd2A-obd1 jumper harness. And I'm interested in running a jdm ecu. Not interested in chipping an obd1 ecu or tuning. I want to run an oem ecu. Stock.

I have done a little bit of reaearch about what is available for sale. But when I try to look up specs... I find very little.

It seems that the only info available on jdm ecu's is for vtec applications. Or vague specs on the b-series wiki page.

Anyway, the stock JDM ecu's for b20 engines I've been able to find are P3G, P7J, & P8R.

I realize the P8R ecu is a match for b20's with a P8R head. And I don't have one of those. So....

Does anyone have any information on these non-vtec ecu's ?

Does anyone have any experience running any of these ecu's ?

Anything that may need to be added or modified to make this work ?

Any help is appreciated.

· Registered
195 Posts
Discussion Starter · #2 ·
Ok, so I guess I'm kind of alone on this thread. Ha.

Just in case anyone is interested, I decided to go further with my idea of getting a stock ecu for my low comp B20B. I picked up a JDM Step Wgn ecu. A P3G-981. It's a stock ECU for a low comp B20B.

It's one of those big box JDM obd1 ecu's with 4 plugs that is not chippable. Which is fine. I just want the stock maps.

I got a good deal on the ECU from an importer. However, after testing it I found the O2 heater circuit in the ECU is faulty. It was throwing a false code 41.

I contacted the importer and they were really understanding. They refunded me & let me keep the ECU. So I figured I would try to look into fixing the faulty ECU since it was free.

But...I couldn't find any information online about repairing ECU's or board maps or technical cad drawings or whatever else techs use to diagnose these things. So I guess the few people who do know are keeping this information to themselves.

I have a little experience repairing simple circuits. So after tracing the circuit paths by hand with a multimeter, I found that the heater circuit is controlled by a "SI 5151S".

I'm not a vtec guy. But I do understand that this chip is used to control vtec in other ecu's and sold in conversion kits. But apparently in this ecu it controls the o2 heater circuit.

So basically I need to figure out if this IC chip is my issue or how else to go about fixing this ECU.

I was hoping to find some advice.

Has anyone tried to repair this issue before ?

I may try to contact HA motorsport and xenocron in the mean time...

I'll report back with some details later.

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6 Posts
Thanks for your post. I have been on a similar type, quest. In regards to sourcing a jdm ecu, engine/vehicle specific matching distributor. For the factory maps, and etc.
I just recently came across a search result. Its a guy who reverse engineered the ecu.

Look up oki micro controller user manual pdf
BRE. Bens rom editor. Hes on github aswell (this might have ecu list containing non usdm

Ill add this next resource.
Hm imports - i have a p8r mid high comp.b20b. 9.2cr
And yes theres few and far sources for b20b or b18b out there
At a time several years back. i had been trying to determine which p8r b20b. I actually had as mine came in the 90 integra id bought
Then one day i had a hunch and sent. Hm motors an email.

I gave a short concise back story about my struggle to find info. And asked if they at their leisure, could entertain an idea and use the engine serial number and back trace it, on the knowledge that japan and us. Keep very well documented in detail of allbthings they export and import. Especially japan i betted. Because of their strict vehicle mileage service limits (japan remives cars with 30k. Miles/km on odomieter
So i figured. Japan would surely notate the serial number of the engine that they take off the road. Andthen export it. And my hunch was right. Found out my b20b. Was from an orthia 2nd gen .
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