Auto to Manual Conversion

[Mason]

I have a 99 Honda Accord 2.3L with a dying automatic transmission. Now that the time’s right, I decided to convert it over to a standard shift. I’ve been grabbing parts for about a week now, but have yet to pick up an ECU. Someone told me if I choose to stick with my current ECU, I won’t have VTEC or VSS, among other things, and obviously I’d like all those things to work. So my question is; do I NEED to find an ECU from a manual Accord? If so, does it need to be the same year, or can it simply be from any manual 98-02 Accord? Can I even look to a 98-02 Acura TL since they’re exactly the same in terms of parts?

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[Mike]

I had the same idea with my 99 Accord but I couldn’t find parts at the time that I needed them, so I ended up overhauling the automatic in it. To answer your question, which I asked to the New York State Inspection officer that was at my work, you don’t need the same ECU as far as inspection is concerned. And as long as it’s for the same F23 engine you have (I have the F23A1), the car should be fine with it.

Here, the state inspection machine looks at the VIN in the ECU and I was asking if I would be red-flagged by DMV if I had a ECU in my car with a different VIN. He told me it looks but it doesn’t care. It will only flag a car that is using a different communication protocol than what it’s supposed to be (it thinks a random dummy car is being plugged in to pass on-board emissions). He said “what about all the cars that get a used PCM installed in them? We’d have an unbelievable amount of flags up it was so particular”,

[Mason]

[quote=”Fopeano” post=128590] And as long as it’s for the same F23 engine you have (I have the F23A1), the car should be fine with it.
[/quote] Okay cool that was gonna be my next question.

But in terms of functionality, it should work fine if I use an automatic transmission ECU with a manual shift? Do they even have the same wiring schematics and ports? I’ve never actually compared the two side by side so I wouldn’t know

[Mike]

I don’t know the side by side difference either, but it should still work with the auto ECU and harness. You’ll just have a bunch of plugs for the transmission that won’t go to anything, and a list of CEL codes to match. As long as any emissions inspection you might be subject to is alright with those codes, then there’s not real NEED to go any further here. You’ll also have to manually wire up the reverse lights and bypass the park/neutral/starter interlock circuit.

[Mason]

Thanks. Will keep posted on any other issues that come up

[Ingvar]

Not from Hondas, from GM vehicles, you MUST have a matching ECM. On newer vehicles, it’s actually TCM, controlled by ECM. If you think about it, there’s quite a bit of difference between how those transmissions operate and by data they send back to ECM. I witnessed quite a few GM owners that failed badly when they tried to shortcut and bypass.
But as far as I know, the older the car, the less finicky all this is and you may get away from using a dedicated ECM. Also, ECMs can be reflashed by dealer to suite a specific transmission, but I think, they go only ten or so years back.
You may also check on proper harness. You realize, harness for AT and MT is quite different, right?

[Lorrin Barth]

This is not something I would try. Not because it can’t be done or won’t work but just because it will end up being more hassle than it is worth. So, unless you are a hobbyist and have no particular time limit for this project I’d suggest fixing or replacing the automatic.

My dd, a Mitsubishi, came with either a 5 speed or a 6 speed manual transmission. The 6 speed proved to be problematic so people often swap to the 5 speed. The parts you need to do that swap fills a page. You could end up owning a donor car to get this done right.

[Mason]

I thought they were different at first, but somehow a friend of mine convinced me they’re similar enough to have no major issues using the automatic harness with a standard shift. After pulling more parts off the Pick-n-Pull car today I realized that they are in fact quite different, but unfortunately the person before me decided to hack up the harness in order to remove it rather than take the extra effort and unplug it neatly, so I’ll have to find another car with a manual harness

[Author]

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