Security Link

The term security link describes the interaction of the GEMS ECM and the alarm ECM. Basically it provides a means to immobilize the vehicle until the alarm has been deactivated (see notes on starting for info).

ITEM MUST BE REVIEWED.

^ P1621 may occur but should only be interpreted as a problem if the vehicle will not start. It is important to distinguish if this is a permanent fault by looking at the freeze frame data. If the fault is stored in freeze frame data, it will be necessary to check out the wiring between the GEMS ECM and the alarm ECM. This code can sometimes occur if the GEMS and BeCM unit "Wake up" at different times. Wake up is the term given to the powering up a circuit/ECM. Code 1621 does not activate the MIL.

^ P1622 may occur when a wiring problem exists or when ECMs "wake up out of synch" with each other. In the field, this may occur if an alarm unit replacement takes place and the MIL does not illuminate after the replacement. Code 1622 does not activate the MIL.

^ The 96 MY Discovery alarm ECM will send out a security code that GEMS does not recognize if not programmed for the NAS market. Once programmed, it will correctly send a code and will not need further programming. Correct code send out can be confirmed by monitoring the MIL after a new alarm ECM is fitted. If it does not illuminate, then the new alarm ECM needs to be programmed.

^ When changing an alarm ECM, if the MIL subsequently fails to illuminate, it is because the substitute alarm unit has a different security code to the one stored in the GEMS ECM. When this occurs, reprogramming of the security code within GEMS is required using TextBook subsystem tests/ECM options/security reprogram. Once selected, the check engine light will illuminate on the next power up sequence.