Installing a Honda P28 ecu chip
While this covers installing a chip on the USDM version (US Domestic Market) Honda P28 ECM, 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).
This requires electronic components soldering skills, especially when working with these ECM circuits, which are sensitive to overheat when soldering and unsoldering parts on it. Also, you may 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 top and bottom circuit board layers.
First, uninstall the ECM from your car. It is be located beneath the carpet in the passenger’s side footrest.
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, the 1K resistor, the two 0.1uf capacitors, the 74HC373 chip, and a wire jumper. The jumper can be any piece of thin wire. A short length cut from the resistor lead will do the job.
Also, have the needed tools handy for this job, which are:
1- A Phillips #2 screwdriver (for removing and replacing the ECM covers)
2- A small flat screwdriver (for prying the chip out of the socket if needed)
3- Small wire cutters or clippers (for cutting excess length of components leads)
4- Long nose pliers (For holding the small parts when installing)
5- 35-watt soldering iron (for soldering/desoldering the parts in the circuit)
6- Desoldering vacuum tool or desoldering braid (for removing parts and cleaning connections)
7- 60/40 rosin core solder
8- Alcohol pads (for cleaning the circuit board from excess soldering flux)
9- Anti-static wrist (for protecting the ECM from static electricity)
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 an earth ground, like a metal conduit of the household electrical circuit. Check #11 of the drawing above for using the electrical household circuit for this. This will protect the ECM and components to be installed. Static electricity may be high enough to damage the ECM if it ever receives a discharge from you.
Start by removing all the 10 bolts (5 on each side) that hold the ECM covers. For the rest of the process, please refer to the drawing below:
On the components side of the circuit board, look for the footprint marks in the circuit, where the parts to be installed belong to. You will find six footprints at the lower right corner of the ECM if you have it in the same position as in the picture above. The six footprints are; “27256”, “74HC373”, “R54”, “C51”, “C52” and “J1”.
If your ECM hasn’t been “chipped” before, you will find the connections on those footprints covered with solder, but no components installed on them. Otherwise, there could already be some of the components in place. In that case, if a socket is installed for inserting the chip, your job will only be pulling the chip installed (if any) and inserting the new chip.
On the other hand, if the ECM has a factory-installed chip, normally done by Honda in some ECMS as a modification for converting from one ECM type to another, then the chip to be replaced will have a copper-colored label on it and will NOT be mounted on a socket.
In the two cases described above, 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 most difficult case, because as mentioned earlier, the factory chip will be soldered with no socket and will have to be removed (desoldered) to be replaced by the 28-pin socket of the kit. Removing a directly soldered chip is not the easiest job in these models because of the already mentioned sensitivity to heat. If any moment after inspecting the job to be done you don’t feel like doing it, I suggest bringing the whole thing to a professional to do it for you.
If you think you can do it your self and decide to do so, one trick for desoldering the chip that can help is to first re-solder all the pins of the chip with excess solder to “rejuvenate” the connections. This will make it easier for the solder to flow when you are pulling it out with the soldering iron and a desoldering vacuum tool.
Desoldering braid will not be very effective for removing the chip. It is used for cleaning out the board by removing soldering from the connections when the parts are already removed and have them opened for inserting the new parts.
This job takes great care and patience, so please take your time to do it right, because although many accidents can be repaired, if an internal connection of the board happens to get broken somehow, may it be because of too much heating or because of too much force pulling the chip, it might be as bad as needing to replace the ECM.
For clearing the connections from solder for inserting the components, spread some solder flux over such connections on the circuit and proceed to remove the soldering by 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 the 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 footprint the corresponding part by soldering it to the circuit. Remember to install the 28-Pin socket instead of directly soldering the power-ROM in the “27256” footprint and make sure you put the pin#1 marking of the socket in the correct orientation to use it as a reference when inserting the chip. Care must be taken when soldering the “74HC373” chip not to (1) overheat it when soldering and (2) not to install it backward, so take note of pin#1 of the “74HC373” chip too.
After installing all six parts and inserting the Power-ROM in the socket, 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 the engine does not go over 3300-4000 RPMs after installing any chip, something went wrong, either with the installation or the chip was not good or not compatible with your ECM. You will find a troubleshooting guide in the link below should you have problems with your installation.
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