ECM/PCM Update
How to substitute the ECM/PCM for testing purposesUse this procedure if you need a known-good ECM/PCM to test a vehicle. It allows you to swap a ECM/PCM from a "donor" vehicle without having to program it to the test vehicle's ignition key.
1. Cut a temporary ignition key for the test vehicle with a non-immobilizer key blank.
2. Remove the ECM/PCM from the test vehicle.
3. Write the test vehicle's VIN on the ECM/PCM you just removed to avoid confusing it with the donor vehicle's ECM/PCM.
4. Remove the known-good ECM/PCM from the donor vehicle, and install it in the test vehicle.
5. Tape the donor vehicle's ignition key head-to-head to the test vehicle's temporary key (A). The ECM/PCM will recognize the code from the donor vehicle's key (B) and allow you to start the engine with the temporary key.
6. After completing your tests, reinstall both ECMs/PCMs, and destroy the temporary key.