Correct, yes it is.
However, if it were me, I'd probably switch to only having the original BSI/CPH, but clone the immobiliser portion of your original ECU to your re-mapped ECU. That way your BSI/CPH is original to the car, VIN correct, keys already programmed to the car, you can then switch between ECUs whilst retaining the immobiliser.
To explain the components of the system in greater detail:
The ECU has a small configuration EEPROM (5P08C3) inside the ECU which contains information about the car it was originally in such as Immobiliser Codes (sync'ed to the BSI/CPH), current stored fault codes, vehicle configuration (AC, Cruise on some models) etc. This portion is _NOT_ downloaded when you download the map (Flash ROM) from the car. The BSI/CPH also contains a small EEPROM, again which contains configuration data (Immobiliser codes which are synced to the ECU, Immobiliser transponder codes, RF Fob codes etc).
The BSI/CPH memory and the ECU's 5P08C3 EEPROM go hand in hand - the ECU won't unlock unless it receives the right code from the BSI - which will only send the right code if the transponder from the key in the barrel sends back the right code to the ECU. Obviously - since you can't just swap the ECU out and expect it to start... However you can clone the 5P08C3 chip with (relative...) ease which will give you two ECUs which will work with the BSI/CPH in the car.
From my limited experience of playing around - any EDC15C2 ECU with the same number number at 0 281 001 362 AND is the same single or three plug connector can run a file from any other ECU with that same number since the hardware is identical. For example:
An ECU with the number 0 281 010 362 can be have the Flash and EEPROM written to an 0 281 010 249 and should work fine - the hardware is (from my inspection...) identical.
An ECU with the number 0 281 010 592 is a 3 plug cannot have it's Flash and EEPROM written to a single plug 0 281 010 249 ECU.
Another caveat is that the EEPROM will need to match the version of the ECU. For example:
A Flash ROM file from an 0 281 001 362 cannot be written to an ECU with the number 0 281 001 249 without the EEPROM being changed. You'll end up with an EEPROM configuration error.
Anyone who knows better - please do shed some light on the technicalities of this - but this is as I understand from my playing on the bench thus far to further understand the EEPROM and Flash ROM contents. When you brick your ECU because you flashed a 512kb jpeg of a penis to your ECU, don't come crying because some bloke on a car forum said it was safe to do so. If you're playing around with flashing stuff to your ECU which is non-standard, you should understand the methods of recovering from a messed up flash. This information is provided with no guarantee that it'll work or is even remotely correct.
However, if it were me, I'd probably switch to only having the original BSI/CPH, but clone the immobiliser portion of your original ECU to your re-mapped ECU. That way your BSI/CPH is original to the car, VIN correct, keys already programmed to the car, you can then switch between ECUs whilst retaining the immobiliser.
To explain the components of the system in greater detail:
The ECU has a small configuration EEPROM (5P08C3) inside the ECU which contains information about the car it was originally in such as Immobiliser Codes (sync'ed to the BSI/CPH), current stored fault codes, vehicle configuration (AC, Cruise on some models) etc. This portion is _NOT_ downloaded when you download the map (Flash ROM) from the car. The BSI/CPH also contains a small EEPROM, again which contains configuration data (Immobiliser codes which are synced to the ECU, Immobiliser transponder codes, RF Fob codes etc).
The BSI/CPH memory and the ECU's 5P08C3 EEPROM go hand in hand - the ECU won't unlock unless it receives the right code from the BSI - which will only send the right code if the transponder from the key in the barrel sends back the right code to the ECU. Obviously - since you can't just swap the ECU out and expect it to start... However you can clone the 5P08C3 chip with (relative...) ease which will give you two ECUs which will work with the BSI/CPH in the car.
From my limited experience of playing around - any EDC15C2 ECU with the same number number at 0 281 001 362 AND is the same single or three plug connector can run a file from any other ECU with that same number since the hardware is identical. For example:
An ECU with the number 0 281 010 362 can be have the Flash and EEPROM written to an 0 281 010 249 and should work fine - the hardware is (from my inspection...) identical.
An ECU with the number 0 281 010 592 is a 3 plug cannot have it's Flash and EEPROM written to a single plug 0 281 010 249 ECU.
Another caveat is that the EEPROM will need to match the version of the ECU. For example:
A Flash ROM file from an 0 281 001 362 cannot be written to an ECU with the number 0 281 001 249 without the EEPROM being changed. You'll end up with an EEPROM configuration error.
Anyone who knows better - please do shed some light on the technicalities of this - but this is as I understand from my playing on the bench thus far to further understand the EEPROM and Flash ROM contents. When you brick your ECU because you flashed a 512kb jpeg of a penis to your ECU, don't come crying because some bloke on a car forum said it was safe to do so. If you're playing around with flashing stuff to your ECU which is non-standard, you should understand the methods of recovering from a messed up flash. This information is provided with no guarantee that it'll work or is even remotely correct.
