Known-Good ECM/PCM Substitution
How to Substitute the PCM for Testing PurposesUse this procedure if you need a known-good PCM to test a vehicle. It allows you to swap a 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 PCM from the test vehicle.
3. Write the test vehicle's VIN on the PCM you just removed to avoid confusing it with the donor vehicle's PCM.
4. Remove the known-good 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 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 PC Ms, and destroy the temporary key.