I know this has been exlained a lot of times over the web but I want to document my experience and the easiest way I found to do it.

OEM P28/P30 ecu internals

So basically this is what you start with. Open your P28 / P30 ECU and locate this part of the board, that’s where the magic takes place.

As you can see, there are 2 missing chips on the PCB, these chips are used when you want to address the ecu maps in an external memory, in this case the 27256 area which is a DIP28 footprint. To do so you need a latch, which is the 74HC373, 2 capacitors for noise reduction (not extremely mandatory), 1 jumper and 1 resistor.

List of components and tool needed to chip a p28 / p30 ECU

Components needed for chipping p28 / p30 ecu

So the shopping cart is:

1x DIP28 wide Socket

1x 74HC373 Latch (Also 74HCT373 can be used)

1x 1K ohm resistor

2x 100nF (0,1uF ) capacitors

1x piece of resistor leg to make a jumper

1x M27C256 eeprom (M27c512 works too but you have to flash the map from address 8000 to ffff)

Tools needed to remove Tin from pads

Also, to be able to do the work you need:

Small tip soldering iron, desoldering braid, Flux, desoldering pump, good soldering tin.

To load a base map you also need an eeprom programmer like Burn2 or similar (i use minipro tl866)

Desoldering and soldering of the new components

Locate the following footprint and start by desoldering the pads which are filled with tin:

  • J1Jumper used to enable or disable external addressing, use a resistor leg to make a good jumper;
  • R54 – 1k ohm resistor goes there;
  • C52, C51 – 100nF capacitors go there;
  • 74hc373 – the same name component goes there
  • 27256 – DIP28 Socket goes there

It will take some time to desolder all the pads, you should ensure that the hole is visible in the pad, so you can slide the component in there:

Closeup of the desoldered pads, ready to accept new components

To successfully desolder pads, wet the tip of the desoldering braid with flux, put it over the pad, press the tip of the iron over the braid which is over the pad until the tin gets transferred to the braid. Don’t overheat the PCB, you need a bit of experience to do this and a lot of patience. Cut the tip of the braid when it’s filled with tin, otherwise it will not accept more tin. When the tin is a lot you can use the manual desoldering pump.

Some people blow compressed air while the tin over the pad is melted. I used to do this to PCB i don’t care about, but an ECU… Should be done properly. Blown tin can go everywhere and create shorts, I don’t like it very much to be honest but it might work for you.

When the desoldering process is finished, start by sliding carefully new components and solder them over the pads.

Final result should be this:

P28 Chipped with socket
P28 Chipped with socket

Now the funny part.. Flash a basemap on the ecu.

Ecu is chipped, now what?

You need an EEPROM programmer. I personally use a cheap minipro tl866 but this is less user friendly compared to a Burn2 unit.

Flashing the EEPROM

Source a basemap for your engine or start from a p28 basemap and load the 32kbyte file on your EEPROM.

Burn2 should allow you to upload the file automatically in the correct address with any of the below Eeproms, but if using any other eeprom programmer use the following rule:

If using a M27c256 load to address 0000 to 7FFF

if using a M27C512 load to address 8000 to FFFF (because this chip can store 2 maps but just the 32kbyte portion from 8000 to FFFF is read by the ECU with the stock pin configuration).

Now you should put the eeprom over the socket like this:

p28 ready to be installed

Install the ecu and start the car. If the revs are limited to 4000 rpm ecu is in limp mode and there must be something wrong either with the map or chip or latch or something else went wrong. If you need to run ecu basemap contained in MCU you should remove J1 which basically restores the P28 to a non chipped status.

That’s all for today, I won’t cover remaps as it’s a whole different (and long) story.

Thanks for reading.