Specifications

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GENERAL OPERATION
General Subaru Immobiliser info.
Immobiliser operation
With the vehicle stopped and the ignition off, there is a red LED on the
dashboard which flashes as an anti theft deterrent with a 0.2 second on time
and a 2 second off time. This indicates the vehicle is in an immobilised state. If
you insert the ignition key and start the engine, the LED will remain off, indicat-
ing no faults are found.
If an attempt is made to start the engine with an incorrect non programmed
key, the engine will start but stop after 2 seconds and the check engine light will
flash- engine cannot be subsequently restarted. If the read only memory plugs
(on early vehicles) are connected, the engine control unit will show code 53- us-
ing the correct transponder will allow the vehicle to be started and the engine
warning light will remain on (because code 53 is stored) until the read memory
plugs are disconnected.
The ignition key utilises a transponder chip which has no battery inside, when
the key is turned on an engine request signal is sent from the engine ECU to the
immobiliser ECU. The immobiliser control unit energises the antenna and ampli-
fier situated around the ignition key barrel. The antenna sends a frequency sig-
nal of 125 KHz to the transponder chip which replies with an ID code. This code
is then sent to the immobiliser ECU which sends it back to the engine ECU and a
conformation signal, if this signal code is the same as is stored within the engine
ECU then the engine function is enabled. All this process takes less than 100
milliseconds. When the ignition is switched off, the rolling code will be updated
to a random value and the engine ECU will send this new code via it's communi-
cation line to the immobiliser ECU. In this way, the engine control unit is ready
to receive the correct code next time the Immobiliser sends it.
If a new Engine or Immobiliser control unit is fitted or if the keys are replaced,
the system must be initialised using the AD100 and appropriate software. Up to
four keys may be programmed using the AD100 and code 53 is "incorrect trans-
ponder code detected"
Specifications
Rolling code. Input of 10 incorrect codes will cause the control unit to shut down
for 10 seconds. A combination scan of all available codes will take approx 432
hours
Antenna uses inductive energy transmission (passive transponder)
Maximum code pick up distance from key approx 3cm
Response time less than 100ms
System current draw 15ma (shut down state)
30ma during code transmission
Power supply 6 - 16v d.c.
Engine control unit EGI situated lower steering column
Antenna frequency 125 KHz
Immobiliser control unit Siemens SWK4690 situated lower steering column or
passenger floor.
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