Honda Accord to TSX Switchblade (Flip) Key Conversion

Obtain a 2009 TSX flip key to use as the donor housing; forum members found them online for roughly $35 against $65-$80 at Acura dealers. Understand the core limitation first: the TSX remote transmits on a different FCC ID than the Accord, so a dealer cannot simply program a TSX remote to drive your Accord's lock, unlock and trunk buttons. A dealer can program the immobilizer alone so the blade will start the engine, but the remote buttons will stay dead. That is exactly why this build moves the Accord's own remote board into the TSX shell instead of relying on the TSX electronics. Buy the blade uncut and have it cut to your key code.

Split the outer case, then open the inner plastic module (the one carrying the Siemens marking). Fully apart, you should be left with the front cover, the button pad, the circuit board, the coin battery, and the back cover. Note the orientation of each piece before setting it aside.

Open the TSX flip key to expose its circuit board and empty housing. Laying the two boards side by side is the heart of the job: the TSX board and housing define where each component must finish, while the Accord board supplies the electronics that actually talk to your car.

Compare the Accord board against the TSX board and mark where the lock, unlock and trunk switches (and the LED, if you keep it) must sit so they align with the TSX button positions. Plan the routing now so the later soldering has a clear target.

Gently lift the lock, unlock and trunk tactile switches off the Accord board; remove the LED as well if you want the indicator to work. Take your time - several builders snapped the tiny legs or terminals off the switches. When freeing each switch, release two opposite corners rather than adjacent ones to avoid twisting and shearing the contacts.

Attach a short length of fine insulated wire to each removed switch and to the LED, so every component can be repositioned away from its original pad without straining a joint.

Seat each switch and the LED at its planned TSX location. Slip a layer of insulating material between every component and the board so nothing shorts against the copper. This step and the two that follow can be done in whatever order the fit allows - work by feel.

Cut each wire to length and solder its far end to the pad it originally served. Because the pads sit very close together, tin and route each lead carefully so neighbouring holes are not bridged by stray solder.

Trace and cut the trunk-button opening out of the white plastic inner cover of the TSX key. A key correction from the thread: the rebuilt board stack ends up too thick to close, so the fob will not seat or align properly. The remedy is to shave a section of plastic out of the TSX inner enclosure (matching jayknight's photos) to make room for the taller assembly.

The key must carry the immobilizer to start the engine. Important: the chip may not be on the circuit board at all. As members discovered on valet and TL keys, the transponder can be buried inside the blade or rotating section of the original key, so check there before assuming it lives on the board. Extract the immobilizer from your original Honda key and fit it into the switchblade. Backing out the retaining screw can strip it easily - go slow, since one builder had to drill his out.

With the board still accessible, verify lock, unlock, trunk, panic and the LED, and confirm the key cranks the engine. Watch for the two documented failure modes: the panic button often stops responding once the halves are clamped together (a suspected pressure short), and the immobilizer or remote may not be recognized if the chip was not relocated correctly. Only close and reassemble the fob after everything checks out.