As you can see in the picture above, the ECU is in our engine bay on the driver's side, between the airbox and fusebox near the firewall.
Step 1 (optional): Using the 10mm socket and ratchet, remove the positive and negative battery terminals and loosen the battery tie down bolt enough to move the metal hook. Swing the battery tie down away from the battery and gently pry up on the black plastic battery box to remove it. Now completely remove the battery.
Step 2: Gently pull up on the black plastic cover surrounding the ECU, it should pull right off with very little force at all. You should now see the three 10mm nuts exposed highlighted in the picture above.
Step 3: Using the ratchet again with the 10mm socket, loosen the nuts until you can turn them with you fingers, but don't completely remove them. You may need to use the 10mm wrench if your ratchet isn't low profile enough to fit on the #1 nut above, the one closest to the firewall. That reservoir there can be kind of a ***** to get a socket on the nut.
Step 4: Hopefully you didn't remove the nuts completely, because the next part will be much easier if you still have some leverage to work with. I tried using my thumb for the next part and had no success, busted out a flat tip screwdriver and problem solved. There are 3 wiring harnesses that clip into the ECU, the way to remove them is to push/pull the black plastic clip towards the driver fender, if done correctly the clip should move completely to the right and you will be able to wiggle the harness out of the ECU with a little force.
Step 5: Now that you have removed the three different wiring harnesses, completely remove the nuts from the threads holding the ECU in place. The bolts don't move, they are a part of the bracket holding the ECU in place, so removing the nuts won't cause the ECU to drop. To remove the ECU push it away from the fuse box to push it off of the threads and just pull out to remove it from the car.
Completing the Reflash
Hondata will not sell their services directly to the public, I'm assuming for tax reasons. So you are forced to purchase the reflash service through an authorized dealer, which can be found on this list:
Dealers. I purchased my reflash through CorSport USA (
CorSport: Honda - 2012+ Honda Civic Si - 2012sireflash), but I am sure there are several other places you can purchase it from. Once you complete the purchase, print 2 copies of your receipt if you want a copy for your records.
Step 1: Now that you have purchased your reflash, package your ECU in a small box preferably with bubble wrap or newspaper. I personally wouldn't use packing peanuts as the metal pins are exposed on the ECU and that could just get messy in the sockets. If you don't have a box, I would HIGHLY recommend taking your ECU to the post office and using their small/medium flat-rate express box.. more on that later.
Step 2: If you purchased online, you should receive an e-mail with this form:
Hondata ECU Reflash Form. If you are impatient like myself and don't want to wait for the e-mail, you can fill the form out yourself. The only caveat is that you will need the dealer's name who you purchased your reflash from. If you purchased through CorSport, the name on the form they sent me was Hybrid Racing. Fill in the other details like name, address, phone, email, etc. Place a check next to ECU/Signed copy of the form/Dealer Receipt. Also next to 2012+ Si, no ****. For application put K24Z7, also no ****. Print the form and sign and date it.
Step 3: Place the ECU in the box,It is very import that you include a copy of your receipt and the signed hondata authorization form. Pick your poison when it comes to shipping, I got a quote for USPS, UPS, and FedEx and for me from AL to Hondata in CA and USPS came up the cheapest by a longshot. Their flatrate express service guarantees the ECU by 3 P.M. the next day and for the box that is the perfect size for our ECU is 39.95, UPS quoted me 66 for overnight and FedEx was 60 as well. You will need to send your ECU to the following address: Hondata, Inc. 2840 Columbia St. Torrance, CA 90503
YES... you can update to flashpro at any time after having the reflash.
well, it must be a technical skill to pull out the ECU. is it that hard? i was just thinking and realized that if a shop will do it for me and it is far from my place. it would consume at least 3 days before it is done completely working. i have to learn it really.. 
