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First of all, forgive any ignorance I may exhibit here. While I'm not new to cars or wrenching, I am new to Hondas specifically, and would greatly appreciate y'all's patience with me as I become more familiar with these platforms and their quirks/specifics. Now that's out of the way, let me explain my dilemma.
I recently purchased a 1999 Honda Civic EX Coupe 5-speed with the D16Y8, and I love the little car. I bought it to be a good, cheap, reliable daily and I've been very pleased with it so far. This past week I needed to perform some maintenance items as the car has 240k miles on it and while things like engine and transmission fluid have been kept up on, it was in need of some TLC to pass a state inspection. Unfortunately those TLC items included front and rear crank seals, as well as an oil pan reseal. That necessitated pulling the motor and trans out, which I yanked as one unit and simply disconnected the ECU and kept the harness with the drivetrain. Here's where I found something interesting.
When I removed the kick panel cover to access the ECU, I found that it was in fact a replacement remanufactured unit from HA Motorsports. Nothing too unusual for a high mileage car, I figured the OEM unit shat the bed at some point after Honda would no longer supply one, or perhaps an OEM replacement was out of the previous owner's budget, no judgement there. When I looked up the part number though, it didn't yield what I'd expected. If the ECU is correctly labeled then it's actually a unit meant for a 92-93 Acura Integra LS/RS/GS. This discovery is what leads directly to my questions.
First, other than the GS-R (which correct me if I'm wrong, but was only offered in the JDM market) no USDM Integra's had VTEC, right? If that's the case, then would this ECU even be able to actuate the VTEC solenoid on my D16Y8?
Second, that generation Integra shows as being OBD-1, whereas this 99 EK Civic was supposed to be OBD-2, I'm thinking this would be why my OBD-2 scan tool couldn't even begin to communicate with the car. I was thinking it may have been the scanner itself dying, and wasn't too worried about it due to the lack of a CEL of any kind, but now I think it's beginning to make sense. Am I correct in this line of thought?
Third, other than potential backorder or parts availability, do any of you have an idea as to why someone may want to use and Integra ECU on an otherwise bone-stock EK Civic? I mean if it was all the shop could get, that's one thing, but I've scoured the web and haven't found any indication of this being a common or proven thing, and in fact have found several sources saying it won't work. Thankfully I can attest to it working at least in the most basic sense, though if it's effectively a VTEC delete I suppose it doesn't entirely work as this engine would want it to.
Fourth, when I was driving the car this afternoon I was getting a little bit more spirited on some backroads, and actually noticed the CEL come on at about 7800-8000rpm and it actually acted as a shift warning /high rpm warning light. I'd seen this happen once in a video on YouTube of a Civic doing some track time but had assumed it was something the owner had programmed into an aftermarket or otherwise tunable ECU. Was that functionality built into Honda ECU's on certain models such as the Integra or Even this generation Civic or is this something added by either HA Motorsports or a savvy end-user?
Fifth and finally, would y'all recommend I source the correct ECU for this car or should I save my money and keep on running this Integra unit? I honestly don't have any complaints about it other than if I'm missing out on VTEC it'd be nice to gain it back. I'm not sure if it's engaging as my typical jam is GM V8's so this thing has very little umph in comparison and I don't have a relevant baseline for what VTEC should/does feel like.
For reference the ECU part number for what's in the car is: 37820-PR4-L11. My limited research indicates that it should in fact be a P2P ECU rather than this PR4.
Thanks in advance for any/all insight y'all are able to provide!
Last edited by Buldg7; 11-05-2023 at 04:49 PM.
Reason: Realized a Typo, misread a reference document and wanted to correct mistake
Okay, when I got home from work I was able to pull the ECU back out and open it up. Now I see why you wanted photos JRCivic1, sure enough this ECU has been chipped. From a brief google of who and what Mugen is, it seems there are plenty of knock-offs of their chips, but if poor fuel economy is typical for the knock-offs then I'd hazard a guess this might actually be genuine. This car has gotten a consistent 35mpg even with me romping on it from time to time. Apart from the part of the board where the Mugen chip is and the Texas Instruments chip beside it which have both been socketed, the only other things that show evidence of tampering are basic components such as diodes and mosfets, likely items that needed replacing when this board was "remanufactured." Other than the warning that the chip is "Not for use on public roads" and the "Mugen" name in Japanese, the outside of the chip seems unmarked. I'm not sure if there's any other outward way of discerning exactly what this chip changes in comparison to the original without removing it and reading the data on it, for which I don't have the equipment necessary.
ebay chipped obd1 integra ls ecu.
i would just remove that ecu and that jumper harness and get the correct ecu for your vehicle.
dont waste your time wondering what and why. there should be no reason that a stock obd2 car should be converted to obd1 except for someone thinking its cool
Alright, update:
I just heard back from the guy I bought the car from, turns out he's the one who did the ECU swap. At some point after he bought it, the CAT rotted out and he had it replaced with a section of straight pipe, and put an anti-fowler on the rear O2 to keep from throwing a CEL. Well apparently he also went and got this ECU, which he describes as "a chipped P28 with a y8 map [and an] economy tune for the catless delete and increased mpg by like 5 or 6." So from the sounds of it, the main motivation was to eliminate throwing a CEL from the lack of CAT with a side benefit of slightly better fuel economy.
After a fair bit more research I now understand what I'm looking at on this ECU. As it turns out, you can convert a PR4 board, such as my 1720 board to support VTEC by adding a few components in otherwise empty locations (the diodes etc. that I mentioned looked to have been tampered with above) and by chipping it with a chip programmed to run VTEC. In fact my research brought me to multiple threads on these same forums describing the process, as well as a page from HA Motorsports going through the exact process in great detail. This explains why the seller referred to it as a P28 even though it's technically a PR4, as it's been modified to be usable as the same. This also confirms that it is in fact running on OBD1, which while mildly annoying for the inability to use my OBD2 reader, isn't really an issue otherwise for me.
At the end of the day, this was some fun 'automotive archaeology' for me, and I just like learning new things. Looks like I'll be sticking with this ECU for the foreseeable future though.
Hello Everyone,
Trying to dive a little deeper into my Honda Civic maintenance, doing some DIY. Bought an OBDII Scanner (16 Pin) with an older Honda Interface Adapter (3 Pin). However when I attempted to find the female connector on the ECU, I found myself in uncharted waters.
The vehicle is an RHD. The ECU is mounted on the left side wall of the front passenger side, below the A-Pillar.
I have done my best to get some pictures of the module, its cables etc for illustration. Need advice on where and how to connect the 16 or 3 pin. Thanks. ECU Rear Femal Socekts Connections ECU Cables Harness Hanging Connector Hanging Connector Inside View ECU Blue Female Socket Rear Right Corner ECU Blue Female Socket Rear Right Corner Inside Closeup
Kalakov222, it is likely that your vehicle does NOT have an OBD-2 16-pin connector. You will have to use the 3-wire data plug for connectivity...assuming that your scanner will communicate using that protocol. If not, you will have to use the OBD-1 method with the 2-wire connector and manually read the CEL flashes. The two plugs that I am referring to are found inside the green rubber plug holder that you have photos of above... the plugs are blue and can be removed from the rubber holder.
Thanks JRCivic1 from some of the pictures and a service manual for similar era models, it seems I am looking for the port in the wrong place i.e. near the ECM rather than under the dash esp driver side, will attempt to find that 3 pin port today and revert with outcome.
In the meantime can you give me some more guidance on "The two plugs that I am referring to are found inside the green rubber plug holder that you have photos of above" the one thats hanging with the 2x 2 Pin female ports?
Also re "the plugs are blue and can be removed from the rubber holder" I dont see any blue plugs on that hanging rubber connector, it seems to be a single piece.
Look at the third and fourth pictures that you have posted above... the green rubber "holder" in the fourth pic has two blue plugs pushed into it (you can see the blue color through the two small rectangle shaped openings in the green rubber holder): In the third pic, you can see the 3-wires going to the plug on the left and the 2-wires going to the plug on the right. Notice that the wires don't go to anything beyond the green holder... the 3-wire plug is used for live data via connection to a HDS or similar diagnostic system. The 2-wire plug is for retrieving codes by connecting the two pins together which begins the display of codes by flashing the "Check Engine" light on the dash.
11-05-2023, 04:41 PM
ECU Mystery, Issue or Not??
