Frequently Asked Question

This table provides details about common Honda ECUs, their common name code, the On Board Diagnostics version, and if they have native functionality to support VTEC lobe switching. The Stock Engine code column highlights what engine(s) that ECU is commonly paired with in a production vehicle.

Honda ECU Part Numbers Decoded​

Honda ECU part numbers are a series of 3 alphanumeric sections.
FORMAT: xxxxx-xxx-xxx

• The first block is the Honda part number denoting it is an ECU. This is almost always 37820.
• The middle 3 digits are the main identifier of the ECU and used in the table above, first column, ECU Code. This code is often associated with the engine or car. for example, a PR3 ECU often has an engine with a PR3 headstamp.
• The Last 3 characters denote the ECU Revision type and each character is a different indicator.
  • The first character indicates market the ECU is intended to support.
    • A - USA
    • C - Canada
    • G - Europe
    • J - Japan
  • The second digit denotes transmission type
    • 0 - Manual
    • 5,7,9 - Automatic
  • The last character indicates the version number and generally does not have any significant changes to connectivity or function. Additional revisions may exist on the ROM inside, which will be indicated on the chip itself.

How to tell if your Honda ECU is Automatic or Manual​

You can tell the type of transmission the ECU is designed to control by the trailing 3-digits in the full model code.

As you saw above the 2nd character in the final 3 of the part number indicates the transmission type. Look for the 0 in that position for manual.

OBD0 ECUs​

(eg, PM6, PR4, PW0, PR3, PM7):
Manual = 000, 001, 002, A00, A01, A10, J00, J001, C01, C00
Auto = J51, J50, A50, A51, 900, 901, A60, C50, C51, X30, A80

OBD1 ECUs​

(eg, P28, P30, P61, P72, P91, P08)
Manual = 000, 001, 002, 003, A00, A01, A02, C00, C01, C02, J00, J01, J02
Auto = J50, J51, 900, 901, 902, C50, C51, C52, A50, A51, A52

OBD2 ECUs​

(eg, P2E, P2P, P2J, P72)
Manual = 000, 001, 002, 003, A00, A01, A03, C00, C01, C02, C03, J00, J01, J02, A11, C11
Auto = A70, A71, A72, A91, A92, C70, C71, C72, C91, C92

Locating the ECU​

The ECU is generally located in the passenger compartment instead of the engine bay. This helps keep it clean and dry and away from extreme temperatures. It is a computer, after all.

• OBD0 cars - usually located under a metal plate in the passenger seat footwell
• OBD1 cars - usually located under the carpet in the passenger seat footwell (on the right side)
• OBD2 cars - usually located behind a plastic panel in the passenger seat footwell