door lockING (Early 95) - quick reference
The doors on 993's through mid-95 are locked with the physical key. The key actuates a switch in the door lock that momentarily grounds the Alarm Control Unit's (ACU) "prime" (lock/arm) or "unprime" (unlock/disarm) input. The ACU responds by driving the lock actuators in both doors. Simultaneously, the ACU arms or disarms the alarm. Limit switches in the lock actuators provide feedback to the ACU informing it of the state of the door locks.
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door locking (Early 95) - Detailed
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door locking (Late 95 - 98) - quick reference
In mid-1995, Porsche introduced the Drive Block system to enhance vehicle security and add remote lock/unlock capability. This upgrade replaced the earlier method that relied on the key and mechanical cylinder lock switches.
With Drive Block, a dedicated immobilizer module, controlled by a new key fob, was added. The fob transmits an encrypted radio signal to the immobilizer, which decodes the request and sends a lock or unlock command to the ACU. The ACU then activates the door lock actuators and arms or disarms the alarm system. The immobilizer only responds to fobs that have been properly paired to it.
As shown in the diagram below, although the method of initiating the command changed—from physical key to remote fob—the downstream behavior of the ACU remains largely the same as in earlier 1995 models. Feedback from limit switches within the door lock actuators confirm the state of the door locks to the ACU.
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door locking (Late 95 - 98) - detailed
