System Description

Control module
The immobilizer, central locking system, convertible top comfort control, radio remote control and monitoring of the vehicle interior functions are integrated in the alarm system. The control module is fitted under the driver's seat. There are 4 versions of the control module:

Versions:

The alarm system monitors the vehicle's outer panels by way of contact switches on the lids and in the doors. Attempted break-ins should be recognized and indicated by audible and visual signals.
The alarm horn, hazard warning lights and interior lights are activated for alarm output.
The system can be extended by connecting additional sensors (glass breakage sensor, tilt sensor).

Central locking
Unlike the previous systems, a two-motor lock is used here.
- locked motor
- safe motor

The locked motor switches the central locking system from unlocked to locked or vice versa.
The safe motor switches the central locking system from locked to safe or vice versa.
The central locking system provides for three different locking conditions:

Action 1: If the lock is activated once, the so-called "Safe locking - door secured" function is activated.
The doors can be opened only with the key, but not with the inside door handles.

Action 2: If the door lock is activated twice within 1 second, the vehicle is not accessible from the outside, but can be unlocked via the inside door handles.

Emergency locking The possibility of activating the door lock three times represents an emergency function. If the functional capability of the overall system is impaired because, for example, one door cannot be closed, it is possible in this way to still activate the other security functions.
Point 1 is activated when the system is operated via the handheld transmitter. The position of the doors is checked by limit switches in the lock.

Fig. 1:

The conditions for a locking process from unlocked to locked are listed in the following table.

Fig. 2:

Fig. 3:

The conditions for a locking process from unlocked to safe are listed in the following table.

Fig. 4:

The conditions for a locking process from locked to safe are listed in the following table.

Fig. 5:

The conditions for a locking process from safe to locked are listed in the following table.

Fig. 6:

Fig. 7:

Fig. 8:

Controlling the interior lights
The interior lights are not controlled directly by the door contacts. The interior lights are switched on:
- When the central locking system is unlocked with a key or via radio transmitter.
- When the doors are opened.
- When Term. S is switched off.

The lighting stays on for approx. 30 seconds.

The interior lights are switched off (doors closed):
- 30 seconds after the central locking system is unlocked with a key or via radio transmitter.
- 30 seconds after the last open door has been closed with Term. 15 and Term. S switched off.
- If both doors are closed with Term. 15 and Term. S switched on.
- When the last open door has been closed with Term. 15 and Term. S switched on.
- When the central locking system is actuated toward position locked or safe via handheld transmitter or door lock barrel and with both doors closed.
- When the last door has been closed, if one door was still open when the central locking system was actuated toward position locked or safe via handheld transmitter or door lock barrel.

The interior lights are switched on and off dimmed.

Opening and closing the convertible top 996 Cabriolet
The second button of the handheld transmitter can be used as a remote control for the convertible top provided that:
- Vehicle is unlocked and deactivated and
- Term. S is switched off for at least 2 seconds and
- Term. 15 is switched off and
- No valid transponder is recognized

If the convertible top is opened or closed, the convertible top control module output is activated first and then (with a 200 ms delay) the comfort opening or comfort closing output.

Load disconnection
If the vehicle is locked up, some loads are disconnected from the supply voltage in order to conserve the battery. Load deactivation is activated if at least one of the following requirements is fulfilled:
- 10 minutes after locking up the vehicle via hand-held transmitter or door lock as well as after re-locking
- 2 hours after term. S is switched off
- 2 hours after the central locking system is unlocked via door lock or hand-held transmitter
- 2 hours after alarm output

Play prevention
If the central locking system is actuated 11 times in less than 5 seconds, further operation is blocked for 30 seconds. If the last command before play prevention activation was a command to open the central locking system, then it is possible to give a further command which is independent from play prevention to close the system. For every further time that play prevention is activated the blocking time is doubled, up to a maximum of 240 seconds. The blocking time is cleared when a door is opened, and if play prevention is activated again, blocking time starts at 30 seconds.

Crash signal
The airbag control module emits a signal to the alarm system control module no later than 35 seconds after Term. S is switched on and until Term. S is switched off again. This signal has a frequency of 10 Hz and indicates two states - normal state (live signal) and crash state. The two states differ in the pulse/duty ratio of the signal:

Live signal 20% high 80% low
Crash signal 80% high 20% low

Signal evaluation begins 45 seconds after term. S is switched on. If no signal is detected from the airbag control module, a corresponding fault is entered into the fault memory.

Undervoltage
If the battery voltage falls below 8.5 V, undervoltage occurs. If the battery voltage exceeds 9 V, the undervoltage is no longer present. If undervoltage occurs, the inputs Door lock barrel open and Door lock barrel closed are evaluated as inactive irrespective of their state. It is not possible to activate the central locking system via the door lock barrel when undervoltage occurs. The alarm system cannot be activated in the case of undervoltage.

Lid release locking
Electric locking of the rear lid release has been omitted as of the production launch of the '98 series. Front lid release locking is still carried out electrically.

Electric locking is carried out by the alarm system control module and is valid for the following country codings:
USA, England and Belgium

Load disconnection is deactivated if at least one of the following requirements is fulfilled:
- Term. S is switched on
- Term. 15 is switched on
- A valid transponder is recognized
- The vehicle is unlocked or locked via hand-held transmitter or door lock
- A door is opened
- Alarm output

Power window control
The control center not only enables power-window control, but also controls the comfort functions. If the central locking button on the hand-held transmitter is still pressed after an unlocking command has been given, the windows are controlled in the direction open. For a locking command with the central locking button on the hand-held transmitter, if the button is still pressed, the windows are controlled in the direction closed (national variant).

Power-on behavior
After the operating voltage is switched on, the system is set to the operating state which it was in before the supply voltage was switched off.

For this purpose, all necessary operating parameters are stored in a permanent memory. If the system was disconnected from the supply in the armed state, this is entered as a fault in the status memory. The same applies if the system is disconnected from the supply voltage during an alarm output. The alarm output is continued as soon as the necessary supply voltage is available.

Activating and deactivating alarm system
The alarm system is activated by a ground signal at the activation input or by an activation signal from the hand-held transmitter.

The activation of the system is ignored if terminal 86 S, terminal 15 or a valid transponder key is recognized.
If for some reason it is not possible to lock the central locking system with a single locking command, the alarm system is not activated. Activation of the alarm system cannot be achieved until the central locking system is locked (if necessary manually) and a new activation command is issued or only locking is performed three times in quick succession. The interval between two locking operations must not be more than 1 second in this case. If the system is activated by this emergency function, the central locking system is locked without checking whether it can be completely locked.

The system saves the type of activation in a status memory. If an alarm is triggered, this information is written into the alarm memory together with the alarm coding.

When the alarm system is activated, the inactive level of all inputs is checked for an inactive period of 10 seconds. Only inputs which are inactive for the entire inactive period can trigger the alarm after the end of the inactive period. All other inputs are blocked for alarm triggering for as long as they are in the active state. If the inactive state occurs at blocked inputs, the inactive period is started for them individually. All inputs which remain in the inactive state during the inactive period are then included in the alarm evaluation.

The inactive period commences immediately after activation:
if it is apparent that the central locking system is locked or if locking occurred three times in succession
and
if the signal "activate is no longer present. (A second activation command for cancelling the anti-theft protection restarts the inactive period.)

In the case of an active signal at the inputs terminal 86 S, terminal 15 or if a valid transponder key is recognized, no activation is possible. If one of these inputs is active at the time of locking, control of the central locking system does not take place. The central locking system is opened if one of these inputs becomes active during the inactive period, since in this case the alarm system is also deactivated.

If, when the vehicle is locked, a door is unlocked after expiry of the 10 second inactive period, this is immediately controlled in the direction "closed". An alarm is triggered at the same time. If, when the vehicle is locked, a door is unlocked from the inside during the inactive period, the central locking system is unlocked and the alarm system is deactivated. (Protection against unintentional locking/activation).

If, within 15 seconds after switching-on of the output External Electronics, movements in the vehicle are detected by the passenger compartment monitor, the central locking system is moved to the locked position and the alarm system is deactivated.

After expiry of the inactive period, the output "External Electronics" is switched on if the alarm-triggering inputs for the doors, convertible top, convertible top compartment cover, front luggage compartment and rear engine compartment were inactive for the entire inactive period. If one of these inputs is active, the output "External electronics" is not switched on until this input becomes inactive and remains in this state for at least 10 seconds.

The switched-on output "External Electronics" cannot be deactivated again by activating one of the above inputs. The output is switched off when deactivation takes place.

If, within a period of less than 1 second after the first activation pulse, a second activation command is issued, the output "External Electronics" is not switched on for one activation cycle. In this case, the central locking system is not secured, but only locked. This is acknowledged by signal 1 at the alarm horn and at the direction indicator light output, as well as during the deactivation period by the display type 3 at the alarm readiness display output and at the display output "Door locked". An opening command deletes the switch off command.

If activation occurs by way of the emergency function (locking 3 times quickly), the output "External Electronics" is not switched on for this activation cycle. This is acknowledged by signal 1 at the alarm horn and direction indicator light output, as well as by display type 2 at the alarm readiness display output. A deactivation command deletes this command.

If terminal 86 S, terminal 15 or a valid transponder key is recognized during the deactivation period, the alarm system is deactivated (protection against unintentional activation). The central locking system is opened in this case.

A system self-test is carried out upon activation. The result of this test is acknowledged via the alarm readiness light and the display "Door locked" and can be called up from the status memory via the diagnosis function. Equipment faults are written into the fault memory. Faults are indicated at the alarm horn and direction indicator light outputs by signal 2.

The alarm system is deactivated by a ground signal at the input "Deactivate" or by a deactivation signal from the handheld transmitter. If a valid transponder key is recognized, the alarm system is also deactivated.

Tilt sensor
The integrated tilt sensor is active analogously to the output Control of External Electronics. During this time, a change in the vehicle tilt triggers an alarm. The current tilt of the vehicle is stored as a reference value during a calibration phase defined for the tilt sensor. The system has an alarm siren with a rechargeable battery supply which can emit an alarm if the vehicle battery is removed.

Behavior in the case of servicing
When removing
- the vehicle battery
- the alarm siren
- the alarm control center

an activated tilt sensor will trigger an alarm. In order to carry out servicing work the alarm siren must be switched off before the work is commenced. To switch it off, insert the vehicle key with valid transponder into the steering lock and rotate to actuate the buzzer contact. Components can be removed with triggering the alarm as long as the vehicle key remains inserted.

Function display and audible checkback
The operating state of the central locking system is fed back via the output "Door locked" and by corresponding activation of the interior light (signals 1 to 3). The operating state of the alarm system is also indicated during the inactive period by the alarm readiness display (display types 1 to 6) and exclusively by the alarm readiness display following expiry of the inactive period. Displayed system faults are always current faults. Previous system faults entered in the status memory have no influence on the function display.

Display type 1 (normal flashing)
Requirement: Alarm system primed no alarm output or no active alarm input after relocking if no alarm input is active

Duration: until deactivation, then Display type 6

LED flashes with a frequency of 0.5 Hz
On time = 100 ms
Off time = 1900 ms

Display type 2 (double flashing)
Requirement: after alarm output or active alarm input after activation or relocking

Duration: until deactivation, then Display type 6

LED flashes with a frequency of 0.5 Hz
On time 1,2 = 100 ms
Off time 1 = 200 ms
Off time 2 = 1700 ms

Display type 3 (rapid flashing)
Requirement: alarm system primed no active alarm inputs

Duration: inactive period, then display type 1

LED flashes with a frequency of 2 Hz
On time = 100 ms
Off time = 400 ms

Display type 4 (rapid flashing)
Requirement: Reception of an adapted handheld transmitter

Duration: push of the button

LED flashes with a frequency of 10 Hz
On time = 50 ms
Off time = 50 ms

Display type 5 (on)
Requirement: after central locking system emergency locking or after locking command is given twice via handheld transmitter or door lock

Duration: in the case of central locking system emergency locking, inactive period then display type 2 in the case of locking command given twice, inactive period then display type 1

The LED is continuously on

Display type 6 (OFF)
The LED is not switched on
In addition the checkback of faults and of the standard status is performed with signal 3 at the interior light output. An audible checkback via the alarm horn output also takes place at the alarm center together with a visual checkback via the outputs for the direction indicator lights.

The following signals are defined:
Signal 1
The outputs are triggered once
On time = 50 ms

Signal 2
The outputs are triggered twice
On time 1,2 = 50 ms
Off time = 200 ms

Signal 3
The outputs are triggered once
On time = 2500 ms

These functions can be switched on and off with the Porsche System Tester 2 depending on the national variants. The times are freely programmable.

Assignment of the display type of the alarm readiness light for the operating state

Fig. 9:

If a control command is issued via the handheld transmitter, this is confirmed with display type 4 for the duration of the operation. This display has priority.

Alarm triggering and alarm output
The alarm functions can be triggered only in the primed state.
A non-blocked alarm input triggers an alarm in the primed state with an active signal. The alarm-triggering input then remains blocked for further alarm triggering until it returns to the inactive state. Then, following expiry of the inactive period of 10 seconds, it is again included in the alarm evaluation, provided that it was inactive for the entire inactive period.

In a priming cycle, the inputs Passenger compartment monitor, External 1 and External 2 trigger a maximum of three alarms.

The alarm output is via:
Horn depending on the country coding
Horn depending on the country coding
Interior lights asynchronous with the direction indicator lights, depending on the country coding

The alarm output with all associated actions is interrupted immediately in the event of deactivation.

Radio remote control
If a command is issued via the handheld transmitter, this is acknowledged with display type 4 at the alarm readiness display for the duration of the operation.
Commands triggered and correctly executed via the handheld transmitter are acknowledged as follows at the output for the direction indicator lights:

Secure with signal 2
Lock with signal 3
Unlock with signal 1

Depending on the country, the checkback signal can be programmed via the Porsche System Tester 2.

All other functions such as interior light control are controlled in the same way as with the vehicle key.

If operating commands are simultaneously present from the handheld transmitter and the door lock barrels, the signal recognized first has priority.