The 1997-2001 Honda Prelude uses an immobilizer system consisting of four components: A programmed key, immobilizer ring (goes around the ignition/key slot), immobilizer control unit (located on the side of the steering column), and immobilizer equipped ECU (located under the passenger side floorboard). All components "talk" to eachother to operate the immobilizer anti-theft system.
The 97-01 Prelude immobilizer equipped ECU will kill power to the PGMFI system if it does not "see" a properly programmed key in the ignition switch, while the immobilizer control unit will kill power to the starter system if it does not "see" a properly programmed key in the ignition switch.
Our ECU immobilizer removal/bypass is available for the 97-01 Prelude ECU's: http://www.hamotorsports.com/immobilizer-removal-service.html
This will effectively bypass the immoblizer system in the ECU and allow the vehicle to run without a properly programmed ignition key.
However, since 97-01 Prelude's also kill power to the starter via the immobilizer control unit, this will also need to be addressed if you don't have a properly programmed key. Thankfully, this is somewhat easy to accomplish with a simple wiring trick. This is ONLY needed if you don't have a properly programmed key. If you DO have a programmed key for the vehicle and are only replacing the ECU, this is NOT needed.
Locate the immobilizer control unit on the side of the steering column. You will need to unscrew the driver's side lower dash cover to gain access.
On the immobilizer control unit, locate the wire harness connector/plug and unplug it from the control unit.
Locate the grey wire and the light blue wire on this connector. Connect the grey wire and light blue wire together. You can solder and heat shrink, or even use a T-tap if needed. Leave the wire harness plug disconnected from the immobilizer control unit. Your starter cut from the immobilizer control unit is now bypassed.