Flash Programming: Notes
The procedure to program Flash Programmable control modules follows all of the preceding steps describing "Exchange control unit". EPROMs are not exchanged for Flash programmable control modules, they have a soldered in, non removable EEPROM.
When connected to the diagnostic connector, the DIS/MoDiC utilize the loaded programming software to communicate with the engine or transmission control module to establish an "authorized unlocked link" with the control module. This link is known as the "seed/key relationship" and is used for the purpose of programming only. The relationship is established as follows:
- The DIS/MoDiC initiates the relationship by requesting the "seed" data from the control module.
- The control module responds by sending the seed to the DIS/MoDiC.
- Based on the received seed, the DIS/MoDiC generates the "key" data and sends it back to the control module.
- The control module then compares the received "key" data with a previously stored value. If they are identical the control module will "unlock" in preparation of programming and send an acknowledgement to the DIS/MoDiC for continuation. If the "key" data is not correct, the control module will discontinue the relationship preventing an "unauthorized unlocking" as a security measure.
- The control module then allows the DIS/MoDiC to erase certain areas of the EEPROM to provide space for new data when an update is being performed or program all of the data for when a new basic module is being installed into a vehicle.