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7) Immobilizer Control
(1) Overview
The Immobilizer System provides an additional theft deterrent to the vehicle in which it is installed and
prevents it from being started by unauthorized persons. The transponder integrated in the key and the
engine control unit have the same code. When the ignition key with the integrated transponder is turned
to the ON position, the ECU (Engine Control Unit) checks the crypto code of the key and, if correct,
allows the vehicle to start the engine.
For details, refer to Chapter "BCM".
(2) Components
Conditions for cooling fan ▶
Immobilizer
antenna
Immobilizer
key
Start motor
Instrument
cluster
BCM
G20DF ECU
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Key approval process ▶
When turning the ignition switch to ON position, the power is supplied to BCM and ECU. ECU
communicate with the immobilizer key to check if it is valid crypto code. If it is valid, ECU start to control
the engine when turning the ignition switch to START position.
The system has 10 seconds of valid time-out period. If the engine does not start in this period, the key
approval process should be done again.
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Measuring at (-) wiring ▶
Measure the voltage between battery wiring
and body ground. -
Specified valuebelow 0.3V
If the voltage is out of the specified value,
check the wiring mounting bolt for corrosion
and looseness. If there is a poor contact due
to corrosion or paint, wipe out the contact area
and retighten it.
Wiring mounting bolt to body
ground (-): 17 Nm
Measuring the battery voltage ▶
Stop the engine and wait for 20 minutes.
Measure the voltage between terminal (+)
and terminal (-) with the ignition switch OFF
and all electric devices OFF. -
Specified valueover 12V
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Measuring the voltage drop between lines ▶
Measure the voltage drop between alternator B+ and battery B+. -
Specified valuebelow 0.3V
If the value is out of the specified value, check the terminal and clamp for looseness.
Checking the charge warning lamp ▶
<007b009c0099009500470096008d008d00470088009300930047008c0093008c008a009b00990090008a0047008b008c009d0090008a008c009a004700880095008b00470097009c009b0047009b008f008c00470090008e00950090009b00900096009500
47009a009e0090009b008a008f004702c80076007502c90047>(Pre-warning).
Check if the charge warning lamp goes out.
If the charge warning lamp does not go off, inspect the electric circuit.
Start the engine and check if the charge warning lamp keeps off. 1.
2.
-
3.
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Operation of charge warning lamp ▶
ECU checks the generating voltage from alternator and circuit conditions and sends the warning lamp ON
signal to meter cluster through CAN line.Basic control logic according to the driving conditions ▶
Engine ECU determines the engine loads according to the fuel injection volume and engine speed. It
charges the battery by increasing the generating voltage during deceleration. To improve the fuel
economy by reducing the alternator load during acceleration, engine ECU decreases the generating
voltage and consumes the battery voltage.
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2. CHECKING CABLES AND WIRES
Check for loose connection or rust.
Check terminals and wires for corrosion due to electrolyte leakage.
Check terminals and wires for open circuit.
Check the wire insulation and coat for damage, cracks or deterioration.
Check if the conductive parts of the terminals do not contact with vehicle body or other metal parts.
Check that the grounding part has continuity with mounting bolts and vehicle body.
Check that wires are properly routed.
Make sure that wires are securely fixed to avoid contact with sharp body parts and high-temperature
parts, such as the exhaust manifold and exhaust pipes.
The rotating parts, such as fan pulley and fan belt, perturbative parts and wiring should be secured
tightly at regular intervals.
Secure the wiring between the fixed parts, such as the vehicle body, and vibrating parts, such as the
engine, after slackening it slightly to prevent it from being damaged. -
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2. IMMOBILIZER/REMOTE CONTROL KEY CODING
1) System Overview
While the communication between BCM/SKM and ECU is based on the CAN communication, the
communication between transponder and BCM/SKM is based on LF (Low frequency) and RF (Radio
frequency). When the ignition switch is turned to ON position, the BCM checks the verified transponder
according to the immobilizer verification procedure, if correct, allows the vehicle to start the engine. The
immobilizer indicator comes on during the communication and if the verification is carried out
successfully the indicator goes off.
If there is something wrong in the system, the indicator blinks.
2) System Layout
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3) Operation of Immobilizer
When the ignition switch is turned to the ON position with REKES key, the BCM checks the crypto code
of the inserted key using the immobilizer antenna and sends whether the engine is startable or not to the
engine ECU through the CAN communication so that the engine can be started.
BCM
REKES key
Immobilizer antenna
ECUCAN line
For the vehicle with the immobilizer, there can be a problem in starting the vehicle or the system error:
When two or more immobilizer keys come into contact with (each) other(s).
When the key is close to any device sending or receiving electromagnetic fields or waves other
than Ssangyong products.
When the key is close to any electronic or electric devices such as lighting equipment, security keys
or security cards.
When the key is close to a magnetic or metal object or a battery. -
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