Installing a Honda P28 ecu chip

How to install a P28 chip.

While this covers the Honda P28 ECM, the USDM version (US Domestic Market), the procedure is the same for almost all 1992-1995 (OBD-I) Civic and Integra ECMs. The circuits of all of them are based on the same construction design. Those are, but not limited to, the Honda P05, P06, P08, P28, P30, P72, P75, and PR4 (OBD-I version).

These are step by step installation instructions, but it still requires electronic components soldering skills, specially when working with these ECM circuits, which are very sensitive to overheating. Also, you will find it somewhat difficult to desolder parts from these circuit boards, because of its multi-layer structure. Multi layer means that it has connections above, below and inside the circuit board layers. These circuits, besides the top and bottom circuit layer, it may have from one to many internal layers.

You must start by uninstalling the ECM from your car. It is be located beneath the carpet in the passenger’s side foot rest.

Once you uninstall the ECM from the car, place it on a bench or flat table for working it out. Have handy all the parts in the kit, which are; the Power-ROM chip (from Honda Performance Chips), the 1K resistor, the two 0.1uf capacitors, the 74HC373 chip and a wire jumper. That last one, it can be any piece of thin wire. A cut lead from the resistor will do the job.

Have also handy the tools needed for the job, which are:

1- A Phillips #2 screwdriver (for removing and replacing the ECM covers)
2- Small flat screwdriver (in case it is needed to remove a chip or component by gently prying)
3- Small wire cutters or clippers (for cutting excess length of the leads, etc.)
4- Long nose pliers (For holding the small parts when installing)
5- 35 watt soldering iron (for soldering the parts in the circuit)
6- Desoldering vacuum tool or desoldering braid (for removing parts and/or cleaning connections)
7- 60/40 rosin core solder
8- Alcohol pads (for cleaning the circuit board from excess flux)
9- Anti-static wrist (for protecting the ECM and components to be installed)
10- Soldering flux (liquid or paste, for electronic soldering – DO NOT use plumbing or any acid flux)

Before starting, plug the soldering iron in so it gets ready to use in a few minutes. Also, make sure you put on the anti-static wrist and connect the other end to a good earth ground, like metal conduit of the house hold electrical circuit (mechanical or safety ground) or a cold water metal pipe. Check number “11” above for using the electrical house hold circuit for this. This will protect the ECM and components to be installed, since static electricity may be enough to damage electronic equipment or electronic components.

Start by removing all the 10 bolts (5 on each side) that hold the ECM covers. For the rest of the procedures, please refer to the drawing bellow:

On the components side of the ECM’s circuit board, search for the place marks (footprints) in the circuit where the parts to be installed belong. You will find six place marks at the lower right corner of the ECM, if having the ECM in the same position of the picture above. The six marks are; “27256”, “74HC373”, “R54”, “C51”, “C52” and “J1”.

If your ECM hasn’t been tampered with, you will find the connections on those place marks, covered with solder. Otherwise, there could already be some components installed already in those places. In that case, if a socket is installed for inserting the chip, your job will only be pulling one chip out and inserting the new one.

On the other hand, if the ECM has a factory installed chip, normally done as a modification for converting from one ECM type to another, the chip to be replaced will have a copper colored label on it and will NOT be mounted on a socket.

In these two cases, the “OBD-I Kit” will not be needed, except for the socket in the factory chip case. About the factory chip case, it would be the worst case, since the factory chip will have to be removed (desoldered) to be replaced by the chip socket. Removing a direct soldered chip is not the easiest job and if it was poorly installed and if you don’t have the needed experience or tools, I suggest to bring the whole thing to a professional or there is a risk of damaging and loosing the ECM.

If you decide to do it yourself anyway, one trick for desoldering the chip that can help, is to first re-solder the chip entirely with excess solder to “rejuvenate” the connections and then remove the solder with the soldering iron and a desoldering vacuum tool. In this case, desoldering braid will not be very effective. This will take great care and patience, since the circuit board, as explained above, is multi-layered and will not release the soldered parts easily.

If an internal connection of the board is broken, it might be as bad as needing to replace the ECM, although some accidents can be repaired. Again, great care should be taken doing this job.

Ok, for now on, let’s keep going with the ECMs that has no components previously installed.

Spread some solder flux over the pin connections on the circuit that is covered with solder and proceed to remove the soldering using the soldering iron and either, the desoldering vacuum tool or the desoldering braid.

The connections on the board should remain opened and you should be able to look through the holes after solder is correctly removed. After this is done on all the footprints of all the marked components, clean the circuit of excess soldering flux with the alcohol pads.

Installing the parts

After cleaning all the pin connections area with alcohol, install on each place mark the corresponding part by soldering it. Remember to install the 28-Pin socket instead of directly soldering the power-ROM in the “27256” area. Care must be taken when soldering the “74HC373” chip NOT to (1) overheat it when soldering and (2) NOT to install it backwards.

Please refer to the pin orientation drawing below, when inserting the Power-ROM in the socket and when soldering in place the 74HC373 chip.

After installing all six parts and inserting the Power-ROM, just put back the ECM all together and re-install it in your car.

The following table contains a list of the parts in the installation kit and their reference numbers on the circuit board, along with a brief explanation of their function in the circuit. Use it as a reference for easier location and installation.

NOTE: If your car does not pass the 3300-4000 RPMs after installing a chip, something went wrong, either with the installation or with the chip it self. You will find a troubleshooting guide elsewhere in this website. Just use the search area and search “troubleshooting honda p28 installation”.

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19 Responses

  1. admin says:

    For those of you that might be wondering, “R54” is picked to be a 1k (1,000 Ohms) resistor, but values as high as 10K (10,000 Ohms) are being successfully used. This part is not critical as you can see, so if you can get a value from 1K to 10K, it will work, though the closer to 1K, the better.

  2. admin says:

    One more thing, the jumper “J1”, as mentioned before, is to enable the reading of the external ROM you just installed (the chip). So, as you might be guessing so far, yes, it can be replaced with a switch to enable or disable the external ROM reading mode of the ecu, then enabling or disabling the extra power!

    If doing so, please bear in mind that switch wires must be kept short to prevent electronic noise from being picked up like an antenna would do, and entering to the computer circuit, which might make it to behave erratically or to lock up on times. No more than 2-3 feet should be ok.

    Also, many computers will require to turn off the engine and then on, for changes to take effect, while others will allow changes “on the fly”.

  3. Ben Perkins says:

    these ecus are easier than some others because there is no chip in place where you are goind to work. contrary to other that you have to remove the stock chip. good info.

  4. admin says:

    That is right. Civic and Integra OBD-I ecus are easier to chip than their counter part OBD-I Accord and Prelude. On the first ones, you just remove soldering from the footprint and insert the parts. On the others, you must desolder the factory parts first, so the new parts can be inserted ans soldered. Nevertheless, for both jobs, skills on electronic circuit soldering and electronic parts management are required.

    Thanks for reading,


  5. jeff says:

    for the j1 what kind of wire are you reffereing to wire as in metal wire or wire as in a wire you run power through

  6. admin says:

    Hello Jeff.

    Either one. Just a jumper. It could be a piece of the leads of the resistor, a small piece or speaker wire or even a small paper clip. Something to make an electrical connection between the two points of “J1”. If it is a bare metal wire (no insulation), like a cut lead from a resistor, just make sure that it connects to the two points marked in “J1” and do not touch anything else.



  7. admin says:

    Guys, as many have asked this, on the P72 (94-95 Integra GSR) and P74 / P75 (1994-1995 Integra LS) the resistor R54 is NOT needed.



  8. Martin says:

    With installing this chip,how large a performance I may count on an increase?

  9. admin says:

    Hello. Performance from these chips vary from engine to engine, depending on #1 setup, #2 how good is the engine mechanically and #3 the weather and altitude where it is being used.

    It will be anything form 2 BHP to about 10 BHP. The number might seem low, but the feeling will definitively tell the contrary and one single horse power may be the difference between winning or loosing a race or for less time in a quarter mile.

    As usual, the recommendation is, the cooler the air entering the engine, the these chips will performs as cooler air is more dense than hot air, thus containing more oxygen concentration.

    As an example for that, people who live in a hot weather Country, will experience small boost in power when driving at nights because of lower temperatures than at day time.


  10. Martin says:

    The engine d16z6, wm 4-1 complete exhaust system,5 kg of flywheel, cold air intake.
    The engine went through a full renovation.
    Largest performance until now 20celsius in a degree,
    6400 turn s20-as with bill. (5–gears)(195/50×15).
    A chip would be needed for this configuration!
    Your proposal?
    In Hungary the average temperature of my lodge, the climate (in summer 25-32c degree).

    Thank you!

  11. admin says:

    Hello Martin. For the D16Z6, the P28 is widely used, but since you are located in Hungary, I guess that your ecu is not an USDM model.

    While all your mods are compatible with our chips, a chip for your car will depend on your ecu more than anything, so if you please let me know the complete number of your car’s ecu (“37820-P??-???”) I will be able to tell you for sure.


  12. Martin says:

    Ecu numbers:37820 P28 G01

  13. admin says:

    Hello Martin. Thanks for replying. Yes we sell the exact chip for that ecu that will go great with your mods, but right now they are in backorder.

    There were an unexpected massive sale and we ran out of them. We are expecting them in a week or so. Anyway, the link is below, just in case you want to check once in a while for availability.

  14. Teodorasny says:

    Very interesting information.

  15. Pete says:

    Thanks for this info. i just bought a chip from ebay and it didn’t include instructions. anyway i installed the chip and it fills little or no difference. it was pretty cheap anyway, so i guess i got what i paid for…

  16. Ricardo says:

    i have a P28 ecu and i want to convert to a P30 what chip i heve to buy?

  17. Richard says:

    You should buy then a P30 chip, but make sure that the conversion is made right, as must P30’s out there are JDM ecms, contrary to P28, which is USDM.

    If you convert it right (I guess P28 to an USDM P30) then you will just need a chip for that USDM P30.

    I hope this helps. For any other question you are welcome back.


  1. December 20, 2008

    […] Vote Installing a Honda P28 ecu chip […]

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