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”.