Honda ECUs have a Diagnostic Generation, Model and a Board Revision.

The diagnostic generations are OBD 0, OBD I, and OBD II.

Examples of the model are  P28, P72, etc.

The board revisions are 1980, 11F0, and 1720.

Diagnostic Generation (OBD 0, OBD I, OBD IIa/b)

Every generation

From top to bottom:

Knowing the generation of your ECU is extremely important. For a P28 it is easy because the P28 was only made for OBD I vehicles, however Integra ECUs like the P72 and P75 have both OBD I and OBD II variants. Be weary of this when you are purchasing an ECU online, an OBD II ECU is basically worthless.

Model (P28/P72/etc)

Side view of P28

Just because you have an OBD 0 or OBD I ECU doesn’t necessarily mean that you’ll be able to just up and tune. Take a look at the side of your ECU, you’ll see 37820-PXX-XXX. The numbers following the P, like P28 or P30 are very important. Here are some things to note about the most common variants:

• P05 – Civic CX – Most basic supported ECU. Doesn’t have O2 Heater circuit, disable this to prevent CEL
• P06 – Civic DX – Same as P05 but has heater circuit
• P08 – JDM Civic – Same as P06, but has VTEC
• P28 –  Civic Ex/Si – The standard issue tuning ECU.
• P30 – Del Sol VTEC – Same as P28 but has a Knock Board
• P72 – Same as P30 but with IAB control
• P75 – Same as P72 but with no Knock Board or VTEC control

Board Revision

The only reason that the board revision is typically of interest is when you are attempting to add components like a VTEC conversion kit.

The board revision can be found silkscreened onto your ECU:

This is a 11F0 board

USDM/JDM

The only time you need to worry about whether your ECU is UDSM or JDM is when selecting which chip kit to purchase. JDM ECUs require slightly different chips than their USDM counterparts, so make sure you select the right one when you order.

USDM (Rectangular)