Tool list:
10mm socket
A Sharpie
Drill
A #9 drill bit
Hammer
Drift punch
6mm x 1.00 tap
Scissors
Parts list:
P12 ECU - $20-$100, depends on where you find it and how much you are willing to spend.
Foam (two different types) - $0-$20 (all depends on if you have some laying around or if you have to buy some)
Two or four 6mm x 1.00 metric nuts (optional) - $0.16-$0.32
Thread lock - $1 or $2, you should just have some laying around.
I am only providing this as a reference. What you do and how you do it is all up to you. I am not responsible for any damage caused to you, your vehicle, family, friends, dog, the cute little girl next door, or anyone or anything else.
Proceed at your own risk.
After seeing how sloppy of a job several people I know did on their ECU swap I thought I would share my two cents and provide my solution on how to safely secure a P12 ECU on our cars.
First a few questions that came up during this whole thing.
Q. What vehicle does a P12 ECU come from?
A. The P12 ECU comes from a 92-95 Prelude S with the F22A1 motor.
Q. Where can I buy/get a P12 ECU?
A. Junkyards, eBay, even here on CB7tuner. Just ask around, if you really want one, you'll find one.
Q. Why do I need to secure the P12 ECU? I thought it was a direct swap?
A. It is a direct swap, just that the mounts on the P12 do not line up with any of the OEM spots.
Q. Can't I just install it and not worry about fastening it to anything? Isn't there a cover that goes over all of it anyways?
A. Yes there is a cover that goes over it, in fact the stock ECU is bolted to that cover. And yes you can just install it and not worry about bolting it to anything, however the original ECU is bolted to the cover for a reason and I would think that a vital part of the vehicle is better off being securely fastened to something and not just kinda rattling around.
Q. Seems like Honda knew what they were doing by bolting down the ECU, so yeah I want to secure the ECU, how do I do it?
A. Just follow these steps and you'll be rocking a brand new safe and secure P12 ECU.
Step 1: Getting to the ECU
Disconnect the negative battery terminal from the battery (duh). Once that is done remove the door sill and kickpanel trim on the passenger's side, then pull back the carpet. The ECU and TCU (if equipped with an automatic transmission) are attached to the cover plate, so with the carpet pulled back remove the four 10mm nuts that are holding the ECU cover plate down. Once that is done disconnect the wiring harnesses from ECU and TCU (if equipped). Once the four nuts and the wiring harnesses are disconnected the entire ECU cover plate can be removed from the car for easier access.
This entire procedure has been covered in several other DIYs so I didn't feel like this needed to be covered in depth.
Step 2: Removing the old
Once you have the ECU cover removed from the car it's time to removed the ECU.
^The cover removed from the car for easy access of everything.
If you have an automatic like I do, the TCU will have to be removed first to access one of the bolts that is holding the ECU to the cover.
^TCU removed. Notice the bolt that it was hiding.
Once everything is removed from the cover, I placed the the P12 ECU next to the stock ECU, no mounting holes lineup.
^Stock ECU on the left, P12 on the right. Not even close to the same mounting holes.
Step 2a: Finding the correct location (automatic transaxle vehicles)
If you have a manual, skip to Step 2b because you can mount the P12 ECU anywhere on the cover plate.
However for those of us who do have an automatic, here is what I did to mount the P12 next to the TCU.
First line the TCU up with it's original mounting holes on the cover plate. Then place the P12 ECU next to it like so:
Holding the P12 in place, remove the TCU and mark the center of the two mounts of the P12 ECU with a Sharpie. The other two mounts on the ECU are not going to get used/will not mount to anything, don't worry about it because two bolts will hold it pretty securely when everything is all said and done.
Step 2b: Finding the correct location (manual transaxle vehicles)
Place the P12 on the cover plate so that the ECU is facing the same direction as the stock one and so that the wiring harnesses will reach/plug into the P12 (approximately even with the edge of the cover plate). Then mark the center of all four mounts of the ECU with a Sharpie.
Step 3: Making some holes
So now with your new mounting holes marked on the cover plate, take a drift punch and line it up on your Sharpie marks and dimple the cover plate like so:
^Closeup
These dimples will prevent your drill bit from walking.
Now get your drill and a #9 drill bit out and drill your holes.
Holes drilled!
Now get out your 6mm x 1.00 tap and tap all of the holes like so:
^Tapping the holes
Once that is done, make sure the original bolts fit:
^Bolt fits perfectly
Step 4: Finish mounting and rattle prevention
Before you finish mounting the ECU on the cover plate, take some closed cell foam and line the entire thing.
^Foam added to cover plate
This will give the ECU and TCU (if equipped) a cushion and prevent it from rattling. I used some OverKill from Second Skin Audio, uncompressed it's about 1/8" thick but it will compress down close to 1/32".
Place the P12 on the cover plate and bolt it down to the new holes you made. If being installed on an automatic vehicle you should only have two bolts holding it on the cover plate. On a manual vehicle you should have four bolts holding it.
On the backside of the cover plate the bolts will be sticking through, this is when you get your thread lock out and apply it to the exposed threads. Then get your 6mm x 1.00 metric nuts and thread them onto the end of the exposed bolt and snug everything down. This is just for insurance and is an optional step.
Once you have the ECU secured, reinstall the TCU (if equipped), plug all of the wiring harnesses in, and reinstall the four 10mm nuts that secure the cover plate and you're done!
Your new ECU is safe and secure!
Step 4a: Supporting the ECU (recommended extra step for automatic equipped vehicles)
For those of us who have an automatic, here is an extra step to insure the ECU is secure. Since we can only use two of the four mounting tabs on the ECU, the ECU needs a bit of extra support otherwise it will kind of dangle from the cover plate. To remedy this all you need is some thick foam.
^This foam is about 3/8" thick, compresses fairly easily and will provide support for the ECU.
This foam, just like the other foam, I got from Second Skin Audio and it's called Rattle Pad. Just measure and cut the foam to the same size as the ECU. When you go to reinstall everything, just make sure this foam is underneath the ECU.
^This will give the ECU some extra support when it's installed since only two bolts are holding it to the cover plate.
And just a note for those who are installing it on an automatic equipped vehicle. Since the P12 is approximately 3/4"-1" longer then the stock ECU, it will make it a bit more difficult to get the cover plate back in place because all of the wiring gets in the way. Just take your time and you can get everything to fit back in there no problem, well at least I was...
So there you go, I hope this gives you all some insight and some ideas on how to safely secure a P12 ECU in our cars.
If you have any questions just ask.
If you see any errors (either spelling or technical), let me know.
10mm socket
A Sharpie
Drill
A #9 drill bit
Hammer
Drift punch
6mm x 1.00 tap
Scissors
Parts list:
P12 ECU - $20-$100, depends on where you find it and how much you are willing to spend.
Foam (two different types) - $0-$20 (all depends on if you have some laying around or if you have to buy some)
Two or four 6mm x 1.00 metric nuts (optional) - $0.16-$0.32
Thread lock - $1 or $2, you should just have some laying around.
I am only providing this as a reference. What you do and how you do it is all up to you. I am not responsible for any damage caused to you, your vehicle, family, friends, dog, the cute little girl next door, or anyone or anything else.
Proceed at your own risk.
After seeing how sloppy of a job several people I know did on their ECU swap I thought I would share my two cents and provide my solution on how to safely secure a P12 ECU on our cars.
First a few questions that came up during this whole thing.
Q. What vehicle does a P12 ECU come from?
A. The P12 ECU comes from a 92-95 Prelude S with the F22A1 motor.
Q. Where can I buy/get a P12 ECU?
A. Junkyards, eBay, even here on CB7tuner. Just ask around, if you really want one, you'll find one.
Q. Why do I need to secure the P12 ECU? I thought it was a direct swap?
A. It is a direct swap, just that the mounts on the P12 do not line up with any of the OEM spots.
Q. Can't I just install it and not worry about fastening it to anything? Isn't there a cover that goes over all of it anyways?
A. Yes there is a cover that goes over it, in fact the stock ECU is bolted to that cover. And yes you can just install it and not worry about bolting it to anything, however the original ECU is bolted to the cover for a reason and I would think that a vital part of the vehicle is better off being securely fastened to something and not just kinda rattling around.
Q. Seems like Honda knew what they were doing by bolting down the ECU, so yeah I want to secure the ECU, how do I do it?
A. Just follow these steps and you'll be rocking a brand new safe and secure P12 ECU.
Step 1: Getting to the ECU
Disconnect the negative battery terminal from the battery (duh). Once that is done remove the door sill and kickpanel trim on the passenger's side, then pull back the carpet. The ECU and TCU (if equipped with an automatic transmission) are attached to the cover plate, so with the carpet pulled back remove the four 10mm nuts that are holding the ECU cover plate down. Once that is done disconnect the wiring harnesses from ECU and TCU (if equipped). Once the four nuts and the wiring harnesses are disconnected the entire ECU cover plate can be removed from the car for easier access.
This entire procedure has been covered in several other DIYs so I didn't feel like this needed to be covered in depth.
Step 2: Removing the old
Once you have the ECU cover removed from the car it's time to removed the ECU.
^The cover removed from the car for easy access of everything.
If you have an automatic like I do, the TCU will have to be removed first to access one of the bolts that is holding the ECU to the cover.
^TCU removed. Notice the bolt that it was hiding.
Once everything is removed from the cover, I placed the the P12 ECU next to the stock ECU, no mounting holes lineup.
^Stock ECU on the left, P12 on the right. Not even close to the same mounting holes.
Step 2a: Finding the correct location (automatic transaxle vehicles)
If you have a manual, skip to Step 2b because you can mount the P12 ECU anywhere on the cover plate.
However for those of us who do have an automatic, here is what I did to mount the P12 next to the TCU.
First line the TCU up with it's original mounting holes on the cover plate. Then place the P12 ECU next to it like so:
Holding the P12 in place, remove the TCU and mark the center of the two mounts of the P12 ECU with a Sharpie. The other two mounts on the ECU are not going to get used/will not mount to anything, don't worry about it because two bolts will hold it pretty securely when everything is all said and done.
Step 2b: Finding the correct location (manual transaxle vehicles)
Place the P12 on the cover plate so that the ECU is facing the same direction as the stock one and so that the wiring harnesses will reach/plug into the P12 (approximately even with the edge of the cover plate). Then mark the center of all four mounts of the ECU with a Sharpie.
Step 3: Making some holes
So now with your new mounting holes marked on the cover plate, take a drift punch and line it up on your Sharpie marks and dimple the cover plate like so:
^Closeup
These dimples will prevent your drill bit from walking.
Now get your drill and a #9 drill bit out and drill your holes.
Holes drilled!
Now get out your 6mm x 1.00 tap and tap all of the holes like so:
^Tapping the holes
Once that is done, make sure the original bolts fit:
^Bolt fits perfectly
Step 4: Finish mounting and rattle prevention
Before you finish mounting the ECU on the cover plate, take some closed cell foam and line the entire thing.
^Foam added to cover plate
This will give the ECU and TCU (if equipped) a cushion and prevent it from rattling. I used some OverKill from Second Skin Audio, uncompressed it's about 1/8" thick but it will compress down close to 1/32".
Place the P12 on the cover plate and bolt it down to the new holes you made. If being installed on an automatic vehicle you should only have two bolts holding it on the cover plate. On a manual vehicle you should have four bolts holding it.
On the backside of the cover plate the bolts will be sticking through, this is when you get your thread lock out and apply it to the exposed threads. Then get your 6mm x 1.00 metric nuts and thread them onto the end of the exposed bolt and snug everything down. This is just for insurance and is an optional step.
Once you have the ECU secured, reinstall the TCU (if equipped), plug all of the wiring harnesses in, and reinstall the four 10mm nuts that secure the cover plate and you're done!
Your new ECU is safe and secure!
Step 4a: Supporting the ECU (recommended extra step for automatic equipped vehicles)
For those of us who have an automatic, here is an extra step to insure the ECU is secure. Since we can only use two of the four mounting tabs on the ECU, the ECU needs a bit of extra support otherwise it will kind of dangle from the cover plate. To remedy this all you need is some thick foam.
^This foam is about 3/8" thick, compresses fairly easily and will provide support for the ECU.
This foam, just like the other foam, I got from Second Skin Audio and it's called Rattle Pad. Just measure and cut the foam to the same size as the ECU. When you go to reinstall everything, just make sure this foam is underneath the ECU.
^This will give the ECU some extra support when it's installed since only two bolts are holding it to the cover plate.
And just a note for those who are installing it on an automatic equipped vehicle. Since the P12 is approximately 3/4"-1" longer then the stock ECU, it will make it a bit more difficult to get the cover plate back in place because all of the wiring gets in the way. Just take your time and you can get everything to fit back in there no problem, well at least I was...
So there you go, I hope this gives you all some insight and some ideas on how to safely secure a P12 ECU in our cars.
If you have any questions just ask.
If you see any errors (either spelling or technical), let me know.
for your rep. Freaking excellent job.
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