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Hondata Reflash: 2002-2004 Honda Civic Si (EP3)-A1
Hondata Reflash: 2002-2004 Honda Civic Si (EP3)-A2

Hondata Reflash: 2002-2004 Honda Civic Si (EP3)

Part Number: K20A3-Si

5 out of 55 out of 55 out of 55 out of 55 out of 5 5 customer reviews

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The K20A3-Si program advances the ignition, alters the cam timing and optimizes the fuel for a cold air intake, adding 4-9 ft lb across the rev range.

This program was tuned specifically for a cold air intake, as they give the best power gains. The reflash has been tested with race headers and test pipes and both are safe to use.

This reflash is not suitable with nitrous due to the aggressive ignition advance.

This tune is for 91 octane pump gas. The reflash has not been tested with 87 octane fuel. In the graph above, the change in octane was worth about 2hp and the tuning 8-10. Hondata recommend that 91 octane fuel be used with this reflash.

Only ECU's with part number 37820-PNF-A01 to 37820-PNF-A12 are able to be reflashed.


You are responsible for paying for and sending your ECU to Hondata. You can send your ECU as fast as you would like and shipping costs normally start at $10.00 for ground and $60.00+ for next day air. We recommend using an express service (2 day or next day) through FedEx or UPS because they have the least amount of delivery problems, provide proper insurance, and have good package tracking. We recommend that you do not use USPS because of delivery issues. You are not sending your ECU to K Series Parts you will be sending it to Hondata directly and we provide all of the instructions on where it needs to be sent once your order is approved.


After we approve your order we will send you two emails, one email will be a Hondata form and the other email will be instructions for shipping and what items need to be included. Orders submitted by 3:00pm Mountain Standard Time Monday to Friday are normally approved same day. Orders places after 3:00pm MST or on Saturday and Sunday are processed the next business day.

Hondata normally reflashes ECU's the same day they receive them but they do get busy and it might take an extra business day. We recommend that you plan on a 3 day total turnaround time from the day that Hondata receives your ECU.

Return Shipping

Hondata uses K Series Parts FedEx account to next day air the ECU back to you once the reflash has been installed. This means that you do not have to pay for return shipping. Your ECU will arrive by 3:00pm the day after Hondata completes the reflash installation. Hondata does not provide us with a tracking number or notification when they ship the ECU back to you.

ECU Serial Number

The serial number is located on the ECU. Hondata has provided instructions on how to remove the ECU.

International Customers

K Series Parts cannot sell reflashes to customers outside of the United States per Hondata request. The shipping address must be a US based address.


This reflash is specifically tuned for the USDM 2002 to 2005 Honda Civic Si K20A3


  • 10-12 Peak HP gain depending on the dyno and modifications
  • 4-9 ft lb torque across the rev range
  • Power peak raised 400 rpm from 6300 rpm to 6700 rpm (higher with headers)
  • Rev limiter raised to 7700 rpm.
  • Fully dealer compatible - works with all Honda scan tools and equipment.
  • 0-60 mph times improved by 1 second.


Any increase in RPM limit is at your own risk. If you suffer engine damage that is related to excessive revs Honda / Acura will not cover your warranty.

With regard to aftermarket parts, the law is that warranty coverage cannot be denied simply because such parts are present on the vehicle, or have been used. For more details read the K series FAQ.


Honda may not cover mechanical damage to the engine under warranty resulting from exceeding the factory red line. Hondata & K Series Parts will not cover any damage as a result of installing this product.


Brand: Hondata
Part Number: K20A3-Si
CARB Approved: No

Customer Reviews

4.8 out of 5.0 5 out of 55 out of 55 out of 55 out of 55 out of 5

5 Total Reviews

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Most Recent

5.0 out of 5.0 5 out of 55 out of 55 out of 55 out of 55 out of 5

in-depth END ALL review

By brett on 4/17/2014

OKAY. soo I got my reflashed ecu from hondata and I couldn't be happier. filled up the tank from empty with 93 (91 is cool too; we have 93 in NY) hooked everything up and let it idle for 10 minutes. at first it was making some noise but it went away once the ecu learned the engine again.. first impressions: -the low end is greatly improved. def pulls harder around the 2000rpm area. when accelerating up to the new redline, it pulls allll the way up to the limiter. -you pass 60 mph before you max out 2nd. and that boring k20a3 now sounds like a proper Si. turnaround time: I paid for 3day from FedEx. shipped it on a saturday night and my parents signed for it on wednesday while I was away. that is QUICK. hondata gets an A+ for quickness the reflash gets an A+ for making the ep3 feel more fun to drive like an em1 kseriesparts.com gets an A+++ for handling the transaction the BEST $300-340 (depending on method of shipping) you can spend with an oppurtunity to get kpro down the road stock k20a3 with a injen SRI

5.0 out of 5.0 5 out of 55 out of 55 out of 55 out of 55 out of 5

Re_flash kicks azz

By Sergio on 2/8/2012

Just got my reflash. Dam this runs good now. Love those higher rpms. Has a hell alot more top end. I totaly recomend it. Pulls harder than my brothers 09 si.

4.0 out of 5.0 4 out of 54 out of 54 out of 54 out of 54 out of 5

Reflash was ok, but CRSX is BEYOND excellent..

By William Chu on 5/11/2011

The reflash was decent... I didn't think it was that great of a gain. On the other hand, I love CRSX. Best service! Very prompt and easy to deal with. Never had a problem buy anything from here. a "B" for reflash but definitely an "A++" for CRSX.

5.0 out of 5.0 5 out of 55 out of 55 out of 55 out of 55 out of 5

Crazy Gains

By Dustin on 4/23/2011

This is exactly what the EP3 needs your crazy if you don't do this and shipping is so fast I sent the ecu on Tuesday at about 4:00 from Indiana and had it back Thursday at 1:00. Great purchase I love it.

5.0 out of 5.0 5 out of 55 out of 55 out of 55 out of 55 out of 5


By Bill on 7/19/2010

The reflash seemed to put everthing together. V2,DC,magnaflow now with the download it has much better throttle response, dont skimp on the header it made a sig improvement. Still gettin 30mpg!! must have

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