• Hondata Reflash - RSX Base 2002-2004 AT K20A3

Reflash your 2002-2004 RSX (K20A3 engine) AT engine computer.

  • Fuel, ignition timing and cam timing optimized.
  • Rev limiter raised to 7300 rpm.
  • Power peak raised 400 rpm from stock .
  • 7 Peak hp gain depending on the dyno and modifications (results will vary)
  • 5-10 ft lb torque across the rev range
  • Fully dealer compatible - works with all Honda scan tools and equipment.

This is for an ECU reflash - the ECU is not included.  Hondata does not sell direct - the reflash must be purchased from a Hondata dealer. The ECU reflash form must be sent with your ECU.

We do not recommend the use of nitrous or forced induction for this reflash.


Within the USA this product is legal only for racing vehicles which may never be used upon a public highway.

EPA/CARB status (USA) Competition vehicles only
Model RSX
Year 2002-2004
Market US
Trim Base
Engine K20A3
Transmission AT
Part Number 37820-PND-A51 to 37820-PND-A59


Tuning notes

This car was tuned 91 octane pump gas - which we recommend. As the ignition is advanced there will be less tolerance for poorer quality fuels.

The extra low down torque as illustrated on the dyno chart, may in fact be due to the torque multiplication effect of the torque converter. With an auto transmission, very little time is spent at low RPMs. Most medium throttle openings will bring the engine to about 3000 rpm very quickly.

We do not modify the shift points. These are left at stock. The higher rev limit is accessable in the sportshift mode

When intake, headers and exhausts are added, the power peak is moved above the stock Honda redline. Extending the redline in this case, even if the power peak was not increased will increase your average power.

In the dyno chart above, a shift from 6700 rpm to 5500 rpm (stock rev limiter) goes from 132 HP to 122 HP - an average of 127 hp.

A shift from 7200 rpm (raised rev limiter) to 6000 rpm (140 hp to 132) will give you an average of 136 hp - a 9 hp increase over the typical rev range used under full acceleration.

What if you have modifications?

This program was tuned specifically for a CAI (cold air intake) as they give the best power gains.

Headers have been tested with this program.

Test pipe. This will eventually give you an engine check light telling you have a faulty catalytic converter. We have not seen this error cause any power loss.

If you have nitrous this program will probably not be suitable due to the aggressive ignition advance used.

For consistency in dyno testing we suggest you follow the dyno procedure outlined here.

Will this affect my warranty?

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.

User Review by BlackNite from RSXworld

Let me get the bad outta the way first. The thing costs $605... and there isn't any new hardware to show for it. You keep your same ECU, same hardware, with no backups. Add to the fact that you will be without a car for at least 2 days. I sent in my ECU at 7:30PM on a Tuesday, and got it back Thursday morning at 9:50AM. I live in VA, so that's a very good turn around time however. You have to pay $50 to have it re-flashed if somehow it gets erased and will be without your car again for the same amount of time.

Now to the good stuff. Initial impressions are good. We base owners don't get that awesome peak wheel HP that the Type-S gets... and us Auto RSX owners don't get the big torque bump that the base manual owners appear to get. What we do get is a much needed higher redline to start with. Normally when revving to the fuel cutoff, our power peak comes before the cutoff so our revving past it is only to increase where the revs drop to the next gear. With Hondata, I feel it pull until I hit the cutoff, and shifting to the next gear drops me into allot more power than usual, resulting in a higher average HP, which is really good. Hondata explains this better with numbers: "Extending the redline in this case, even if the power peak was not increased will increase your average power.

I let the car idle for 10min after installing the ECU. I immediately took it for a spin... WOW, the car just seems so much smoother. The more gas I gave it, the more power I got from it. No funky power fluctuations, just a smooth rev band to the top. Smooth, smooth smooth...it's the only way to describe it. I always have and always will use 93 octane in my car, so I can't give you a test on how it reacts to 89... sorry, just can't do it. In a previous email sent to Hondata inquiring about the benefits of using gas rated higher than 91 from me, a reply was sent to me stating that the ECU will take advantage of better fuel. I take it that you'll see a pony or two by using the good stuff and recommend that you do. Here is where I would normally talk about gas milage, but since I haven't gone through that many miles with the ECU or filled up (I've driven it maybe 30 miles at most), I can't really comment on fuel consumption. I don't think it would be fair either since I'm pushing the car hard each ride for performance testing. I'll edit this post on my next fill up. I usually get about 280-300 miles city/highway per tank before my gas light comes on. Take in mind that I drive my car hard all the time, so this will be less than the typical driver gets.

Overall, I am very impressed with what Hondata has done with this ECU. I would love more power, but like they said... our car just doesn't breathe well at higher RPMs. I still have to add my Hondata gasket that is bound to give me a couple lbs of torque down low, and I'm sure headers will net me more power, especially with Intake/Exhaust/Hondata. My goal of 145WHP may be reached with less mods than planned! The 1st 15 second N/A base auto with less than 150WHP is right around the corner. Yes, my goals are small... but it's nice to meet them every once and a while.

Some 2002 onwards and all 2006 onwards ECUs are flash programmable. The ECU can be repeatedly reprogrammed without removing or replacing and internal components.

How do you get your ECU reflashed?

  • Fill out this form
  • Contact your dealer. All sales are made through Hondata dealers.
  • Your dealer or you will need to remove and send your ECU, immobilizer and key to Hondata.

Do I need to send the key & immobilizer?

Only for 2002-2006 RSX and 2002-2005 Civic Si reflashes. All other reflashes do not need to send a key or immobilizer. Flashing the ECU does not in any way alter the immobilizer operation.

How long does it take?

The ECU will be reprogrammed and shipped out the same day it is received. Shipping in the continental USA is FEDEX next day.

Will this affect the fuel economy?

Assuming you drive the vehicle in the same way, no. Fueling at cruise is the same as stock.

Will this affect the engine life?

Provided your engine is maintained correctly this modification should not affect the engine's life.

Will this affect the warranty?

It should not.

Federal law sets forth requirements for warranties and contains a number of provisions to prevent vehicle manufacturers, dealers and others from unjustly denying warranty coverage. With regard to aftermarket parts, the gist of the law is that warranty coverage cannot be denied simply because such parts are present on the vehicle, or have been used. (see Federal Warranty Laws for details). The warranty coverage can be denied only if the aftermarket part caused the malfunction or damage for which warranty coverage is sought.

If a dealership denies warranty coverage (more details here) , they should be willing to do so in writing. Have the dealer describe the failure which is causing your problem AND how the dealer believes the aftermarket product installed is responsible for the problem. Keep an accurate log of all contacts and correspondence in addressing the warranty denial. Hondata will provide any technical information the dealership requires.

With any increase in rev limit there is an increased risk of valve damage. To minimize your risk use the Hondata program with the stock rev limit. All reports of valve damage we have heard have been as a result of miss-shift. The Type S valve springs are good. We have tested a Type S with an 8900 rev limit in a press test vehicle for several months with no problems.

Will any settings be lost?

Your ECU will lose some idle settings and fuel trim when it is unplugged. It will relearn idle automatically if you leave it idling for 10 minutes. As you drive the car it will relearn fuel trim values in a matter of minutes.

Can a Honda/Acura dealer erase this program?

Only if another Honda/Acura update is released could a dealer erase your existing program. If Honda/Acura comes out with an upgrade you are not obliged to have it installed. If you do not wish to have the dealer program installed there is a wire you can disconnect or cut, to prevent reprogramming. The charge for restoring an erased program is $75 (cashiers check or money order) shipping included.  You can also remove pin 7 from the OBD2 port to keep the dealer from reflashing your ecu (DO NOT CUT THIS WIRE).

What about bolt ons?

Most programs have been tested to work well with a variety of intakes and exhausts. No retuning is necessary after an intake is added.  Some programs as tuned specifically for an intake or exhaust, and if so, will mention this in the reflash notes.

If you currently run nitrous, these programs will probably not be suitable due to the ignition advance used. If you want to use nitrous and this program now, you must install a nitrous system that retards ignition.

What about turbo-charging and super-charging?

Use the K-Pro or FlashPro.

What octane is recommended?

For high compression engines (K20A2, K20Z1, K20Z3, K24Z7) 91 octane fuel or better is recommended.  For all other engines there are gains from using higher octant fuel, as the ECU will automatically advance the ignition timing if no knock is detected.

The K series ECU, in order to be re-programmed must have a functioning immobilizer system. Three items must be sent to Hondata: the ECU, the ignition key and the immobilizer. The immobilizer works as normal after the ECU has been re-flashed.

Tools needed:

  • Philips screwdriver
  • 10 mm socket and drive
  • Time needed : 10-15 minutes

Removing the immobilizer (Civic Si, RSX / Integra)

Under the steering column remove the three philips screw holding on the bottom plastic cover.

Depress the bottom cover along its top edge where it meets the top cover to separate the plastic clips. Rotating the steering wheel 45 degrees can help.

Lower the steering column and remove the bottom plastic cover from over the height adjustment lever.

Unclip the green connector immobilizer connector and unscrew the securing two philips screws.

RSX ECU removal

The ECU is located in the passenger's footwell. The kick panel is removed after depressing the centers of three small plastic buttons around the front covering panel.

Unplug the three wiring connectors and remove the two front most 10mm locating bolts, plus the rear bolt. The ECU will slide out easily - if it does not, then check that the rear bolt has been loosened or removed.

K20A3 Civic Si ECU removal

The Civic Si's ECU is located in the passenger's footwell behind the glove compartment.

Unclip the lower plastic panel:

Unplug the three ECU connectors.

Remove the lower two 10 mm bolts.

Open the glove compartment and push out from behind the two bump stops. The glove compartment will drop after this is done.

Undo the last 10 mm bolt and slide the ECU down.

Hondata Reflash - RSX Base 2002-2004 AT K20A3

  • Brand: Hondata, Inc.
  • Product Code: Reflash - RSX 2002-2004 Base AT K20A3
  • Availability: In Stock
  • $295.00