Hello,
The system needs the key to agree with the ECU via the SKIM module.
What that means is that the ECU needs the original SKIM module, or a non-programmed skim module to function, and the key must match the PIN for the SKIM module installed.
In other words, if your old SKIM module works, use it, if not, a used SKIM module will not allow the vehicle to start, even if the key is programmed to that SKIM module.
The solution: new skim/reprogram keys and SKIM, or, new ECU with the SKIM module disconnected.
New ECU's don't use SKIM until it is connected once, but until then, the vehicle will function without anti-theft systems.
If you do replace the ECU and disconnect SKIM module, do not ever plug the skim module back in. Ever.
Lastly, there are ECU programming services that will reprogram the ECU to accept the current skim or deactivate SKIM for you. This will be cheaper than a new ECU, but you still have no anti-theft protection.
Best thing is to get a NEW SKIM module, and reprogram keys and module to ECU.
