Editors note: Originally published by Adam P. on his sub-site, Change Honda ECU from Automatic to Manual. Preserved here in the forums going forward.
This guide will help you identify and change or convert your automatic ecu to a manual version.
Honda Manual or Automatic ECU Identification
First, let's find out if we have an automatic, or a 5 speed ECU. If you don't want to plug it in and throw code 19 (automatic trans lockup solenoid) to find out it is an automatic ECU, then look at the code on the side. If the second to last number is a 5, then you have an automatic ECU (for OBD-1 USDM ECUs). If the 2nd to last # is anything but a five you have an ECU for a 5 speed. If you have a jdm obd-1 ecu, look at the last 3 digits: 900 or...