В хелпе всё написано.

Именно кадилаки я не делал, но концерн один GM, внешне блок как МЕ 7.6.2 (опель), то есть алгоритм работы должен быть как в опеле, а в опеле без car pass делать нечего.
И что эти ребята говорят?? Что они пропишут VIN и машина заведётся?? Даже если это так, то VIN ты сам можешь переписать, но я в это не верю. Или у них есть доступ к базе официалов и они могут сразу и синхру сделать.

Passkey II – The Passkey II system has the Theft Deterrent Module (TDM) function stored in the
Body Control Module (BCM). The TDM portion of the BCM will validate the resistive chip in the
ignition key. If resistance value read by the BCM is what the BCM is expecting, the BCM will send
a message over serial data to the PCM informing the PCM that a valid key is present and the PCM
may start the vehicle.
To perform a relearn on a Passkey II system, make sure there is a fully charged battery in the
vehicle. The battery will be used for 30 minutes without the alternator available for charging.
Connect a battery charger to the battery to ensure power is available while programming. Both
the BCM and PCM must be working and communicating with each other
1. Insert ignition key and turn to the “ON” position. Do not attempt to start the engine. Leave
the key in the “ON” position for approximately 11 minutes. The security light will be steady
on or flashing for the 11-minute period. Do not proceed to Step 2 until the security light
turns off or stops flashing.
2. Turn the ignition switch to the “OFF” position for 30 seconds.
3. Turn the ignition switch to the “ON” position as in Step 1 for 11 minutes.
4. Turn the ignition switch to the “OFF” position for 30 seconds.
5. Turn the ignition switch to the “ON” position as in Step 1 for 11 minutes for a third time.
6. Turn the ignition switch to the “OFF” position for 30 seconds for a third time.
7. Turn the ignition switch to the “ON” position for 30 seconds.
8. Turn the ignition switch to the “OFF” position.
9. Attempt to start the engine.
If the engine starts and runs, the relearn is complete.