How to Substitute the ECM for Testing Purposes

Use this procedure if you need a known-good ECM to test a vehicle. It allows you to swap a ECM from a "donor" vehicle without having to program it to the test vehicle's ignition key.

1. Disconnect the negative cable from the battery on the test vehicle.
2. Cut a temporary ignition key for the test vehicle with a non-immobilizer key blank.
3. Remove the ECM from the test vehicle.
4. Write the test vehicle's VIN on the ECM you just removed to avoid confusing it with the donor vehicle's ECM.
5. Disconnect the negative cable from the battery on the donor vehicle.
6. Remove the known-good ECM from the donor vehicle, and install it in the test vehicle.
7. Tape the donor vehicle's ignition key head-to-head to the test vehicle's temporary key (A). The ECM will recognize the code from the donor vehicle's key (B) and allow you to start the engine with the temporary key.
   Fig 1: Taping Donor Vehicles Ignition Key Head-to-head To The Test Vehicles Temporary Key

   Courtesy of AMERICAN HONDA MOTOR CO., INC.
8. After completing your tests, reinstall both ECMs, and destroy the temporary key.
9. Reconnect the negative cable to the battery.