2003 LEXUS LS430 Diagram AC

Fig. 2: Identifying Engine Immobilizer System Diagram
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1.ENGINE IMMOBILIZER SYSTEM DESCRIPTION
The engine immobilizer system is designed to prevent the vehicle from being stolen. This system uses a
steering lock ECU that stores the key codes of authorized smart keys. If an attempt is made to start the
engine using an unauthorized key, the ECU sends a signal to the ECM to prohibit fuel delivery and
ignition, effectively disabling the engine.
2.FUNCTION OF MAIN COMPONENT
MAIN COMPONENT FUNCTION TABLE
ComponentOutline
Transponder key coil/amplifierWhen key is inserted in ignition key cylinder, key
coil receives key's ID code. Then amplifier
amplifies ID code and outputs it to steering lock
ECU.
Unlock warning switchDetects if key is in ignition key cylinder and outputs
results to steering lock ECU
ECMThrough SFI communication, ECM receives ID
verification results from steering lock ECU. ECM
also verifies ECUs. Then judgement of whether or
not to immobilize engine is made.
Security indicatorDepending on operation of theft warning ECU (theft
deterrent ECU), interior security indicator lamp

CIRCUIT DESCRIPTION
This DTC will be output if the steering lock ECU does not detect that the unlock warning switch is ON even
when the ignition switch is ON. Under the normal conditions, the unlock warning switch is ON when the
ignition switch is ON.
Fig. 29: Push Switch/Key Unlock Warning Switch Malfunction Circuit Description

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WIRING DIAGRAM
Fig. 30: Push Switch/Key Unlock Warning Switch Malfunction
- Wiring Diagram
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INSPECTION PROCEDURE
1.READ DATA LIST USING HAND-HELD TESTER
a. Connect the hand-held tester to the CAN VIM. Then connect the CAN VIM to the DLC3.
b. Turn the ignition switch ON with the key that cannot start the engine.
c. Read the DATA LIST.
Steering lock ECU:
DATA LIST - STEERING LOCK ECU
Measurement Item/

CIRCUIT DESCRIPTION
This DTC is output when a key with a key code that has not been registered in the ECU is inserted into the
ignition key cylinder.
UNMATCHED KEY CODE DTC REFERENCE TABLE
INSPECTION PROCEDURE
1.DELETE DTC AND INSERT ALL PRESENTLY AVAILABLE KEYS TO CHECK WHETHER
ENGINE STARTS OR NOT
OK: Engine starts.
NG: REPLACE KEY THAT CANNOT START ENGINE
OK: NO PROBLEM (BECAUSE OF KEY RE-REGISTRATION)
CIRCUIT DESCRIPTION
This DTC is output when a key that does not have a transponder chip is inserted into the ignition key cylinder or
if communication between the key and steering lock ECU is not possible.
Fig. 34: Communication Malfunction Circuit Description

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WIRING DIAGRAM
DTC No.DTC Detection ConditionTrouble Area
B2795Key with unregistered key code is
insertedSmart key

Fig. 35: No Communication In Immobilizer System, DTC B2798: Communication Malfunction No. 2
DTC - Wiring Diagram
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INSPECTION PROCEDURE
1.READ DATA LIST USING HAND-HELD TESTER
a. Connect the hand-held tester to the CAN VIM. Then connect the CAN VIM to the DLC3.
b. Turn the ignition switch ON with the key that cannot start the engine.
c. Read the DATA LIST.
Steering lock ECU:
DATA LIST - STEERING LOCK ECU
OK: "UNSET" (Ignition switch ON) appears on the screen.
NG: Go to step 2
OK: REPLACE STEERING LOCK ECU
2.CHECK WHETHER ENGINE STARTS WITH OTHER KEYS
a. Check if the en
gine starts with the vehicle's other keys.
Item
Measurement Item/
Display (Range)
Normal ConditionDiagnostic Note
IMMOBILIZERImmobilizer system
status/ SET or UNSETUNSET: Ignition switch
ON SET: Without key-

Fig. 36: Checking Wire Harness (Steering Lock ECU -Transponder Key Amplifier)
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NG: REPAIR OR REPLACE HARNESS AND CONNECTOR
OK: Go to next step
4.REPLACE TRANSPONDER KEY AMPLIFIER
a. After replacing the transponder key amplifier with a normally functioning amplifier, check that the
engine starts.
OK: Engine starts.
NG: REPLACE STEERING LOCK ECU
OK: END
CIRCUIT DESCRIPTION
This DTC is output when a communication error occurs between the transponder key amplifier and steering
lock ECU. Some possible reasons for the communication error are: 1) 2 or more smart keys are positioned too
close together, or 2) noise is occurring in the communication line. Follow the inspection procedure below.
Fig. 37: Communication Malfunction No. 1 Circuit Description

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WIRING DIAGRAM

Fig. 38: Communication Malfunction No. 1 - Wiring Diagram
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INSPECTION PROCEDURE
1.CHECK KEYS
a. Check if the smart key being used is near other smart keys as shown in the illustration. Also, check
if the key ring is in contact with the key grip.
Result:
KEY CHECK RESULT TABLE
ResultProceed to
Key is near other keys and/or key rings is in contact
with key grip.A
Key is not near other keys and/or key ring is not in
contact with the key grip.B

Fig. 41: Checking Wire Harness (Steering Lock ECU -Transponder Key Amplifier)
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NG: REPAIR OR REPLACE HARNESS AND CONNECTOR
OK: Go to next step
5.CHECK OPERATION OF TRANSPONDER KEY AMPLIFIER
a. After replacing the transponder key amplifier with a normally functioning amplifier, check that the
engine starts.
OK: Engine starts.
NG: REPLACE STEERING LOCK ECU
OK: END
CIRCUIT DESCRIPTION
This DTC is output when: 1) the ECM detects errors in its own communications with the steering lock ECU; 2)
the ECM detects errors in the communication lines; and 3) the ECU communication ID between the steering
lock ECU and the ECM are different and an engine start is attempted.
Before troubleshooting for this DTC, make sure no steering lock ECU DTCs are present. If the steering lock
ECU has a key code related DTC, repair it first.
Fig. 42: Engine Immobilizer System Malfunction Circuit Description

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WIRING DIAGRAM

Fig. 43: Engine Immobilizer System Malfunction - Wiring Diagram
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INSPECTION PROCEDURE
1.CHECK WIRE HARNESS (STEERING LOCK ECU - ECM)
a. Disconnect the S46 ECU connector.
b. Disconnect the E2 ECM connector
c. Measure the resistance of the wire harness side connectors.
Standard:
STEERING LOCK ECU - ECM - RESISTANCE TABLE
Tester connectionSpecified condition
S46-13 (EFIO) - E2-6 (IMI)Below 1 ohms
S46-4 (EFII) - E2-7 (IMO)Below 1 ohms
S46-13 (EFIO) or E2-6 (IMI) - Body ground10 kohms or higher
S46-4 (EFII) or E2-7 (IMO) - Body ground10 kohms or higher