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How to install a Chip on 88-91 OBD-0 Honda ECU

DA FUTURE does not assume any responsibility for the use of this document or its information.

Here is a step by step guide toward installing a racing chip on 1988 to 1991 Honda OBD-0 ECUs. First, open up your ECU top cover.

Figure 1
Engine Computer

Figure 2
Remove Top Cover

  1. Open the back panel of the ECU. Figure 3 is a view of the ECU solder side. Trace the Stock ROM Position from the front to the back. Look for a 28 pins chip with the marking Oki 38128, 38256 or a gold sticker in the middle and wording like 27C128 or 27C256. It is usually at the lower left corner away from the ECU Plug (top view). On the solderside is lower right position.
  2. Desolder the stock ROM Figure 4 Use a niddle point soldering iron touching the base of the pin. Do not overheat the Stock ROM, that will distroy it Hold the solder pump close to the heated pin to pump up the solder. Be careful on the grounded pin or pin 1 as they are tougher to desolder.

Figure 3
Solder side of the ECU

Figure 4
Desolder the Stock PROM
  1. Removing the Stock ROM. Figure 5 is a picture from top view of the ECU while the stock ROM chip is being removed. Take extra care while taking out the desoldered stock ROM chip. Use a tweeze to check every pin before moving the chip. Figure 6 showing the stock ROM coming off the ECU. Figure 7 showing the empty slot where the stock ROM use to be.
  2. Removed the Stock ROM. Figure 8 show the stock ROM chip after being removed.The 28 pin IC socket is going to be soldered on the same spot where the stock chip use to be. Figure 9 is the solderside view of the removed stock chip location.

Figure 5
The Stock ROM is being removed

Figure 6
The Stock ROM coming off

Figure 7
The Stock ROM location after being removed

Figure 8
The Stock Rom after being removed

Figure 9
The Solderside of removed ROM location

    Install the 28 pin IC Socket. Figure 10 shows a 28 pin IC socket installed in the removed ROM position. Solder it in place and use multimeter to check any short on the pins. Figure 11  Clean up the solderedside with solvent like thinner or methenol to remove any residue near the pins.

    Figure 10
    IC socket install in stock ROM position

    Figure 11
    Clean up the residue near the pins

    Figure 12
    Install chip unto the IC socket

  1. Insert the New Chip or the old stock ROM in the socket. Figure 12 showing the Racing Chip is being install unto the IC socket. After that, just reinstall the ECU top and bottom covers. Plug the ECU back on the car, reconnect back the battery positive terminal and start the car to check whether the car is runing fine.If you don't any check light and able to rev pass 4000rpm, you have just successfully chip your ECU.