2003 LEXUS LS430 diagram

Fig. 44: Checking Wire Harness (Steering Lock ECU -ECM)
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NG: REPAIR OR REPLACE HARNESS AND CONNECTOR
OK: REPLACE ECM
CIRCUIT DESCRIPTION
This circuit provides power to operate the steering lock ECU.
WIRING DIAGRAM
Fig. 45: ECU Power Source Circuit
- Wiring Diagram

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
transponder key ECU that stores the key codes of authorized ignition 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
COMPONENT FUNCTION TABLE
3.SYSTEM FUNCTION
When the transponder key ECU detects that the unlock warning switch is ON, the ECU provides current
to the transponder ke
y coil and produces a faint electric wave. A transponder chip in the key grip and
ComponentOutline
Transponder key
coil/amplifierWhen key is inserted in ignition key cylinder, key coil receives key's code. Then
amplifier amplifies ID code and outputs it to transponder key ECU.
Unlock warning
switchDetects if key is in ignition key cylinder and outputs results to transponder key
ECU.
ECM
Through SFI communication, ECM receives ID verification results from
transponder key 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 illuminates or starts blinking.

Fig. 27: DTC Reference Chart
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WIRING DIAGRAM
Fig. 28: DTC B2780
- 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.
Transponder key ECU assy:

INSPECTION PROCEDURE
REPLACE KEY
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.
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 transponder key ECU is not possible.
Fig. 33: DTC Reference Chart

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

Fig. 34: DTCs B2796, B2798 - 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.
Transponder key ECU assy:
Fig. 35: Transponder Key ECU Assy Data List

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OK: "UNSET" (Ignition switch ON) appears on the screen.
NG: Go to step 2
OK: REPLACE TRANSPONDER KEY ECU ASSY
2.CHECK WHETHER ENGINE STARTS WITH OTHER KEYS

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WIRING DIAGRAM
Fig. 38: DTC B2797
- Wiring Diagram
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INSPECTION PROCEDURE
1.CHECK KEYS
a. Check if the ignition key being used is near other ignition keys, as shown in the illustration. Also,
check if the ke
y ring is in contact with the key grip.

Fig. 41: Identifying T9 And T8 Amplifier Connector Terminals
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Standard:
TRANSPONDER KEY ECU - TRANSPONDER KEY AMPLIFIER - RESISTANCE TABLE
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 TRANSPONDER KEY ECU ASSY
OK: END
CIRCUIT DESCRIPTION
This DTC is output when: 1) the ECM detects errors in its own communications with the transponder key ECU;
2) the ECM detects errors in the communication lines; and 3) the ECU communication ID between the
transponder key ECU and the ECM are different and an engine start is attempted.
Before troubleshooting for this DTC, make sure no transponder key ECU DTCs are present. If the transponder
key ECU has a key code related DTC, repair it first.
Fig. 42: DTC Reference Chart

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WIRING DIAGRAM
Tester connectionSpecified condition
T9-10 (CODE) - T8-4 (CODE)Below 1 ohms

Fig. 43: DTC B2799 - Wiring Diagram
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INSPECTION PROCEDURE
1.CHECK WIRE HARNESS (TRANSPONDER KEY ECU ASSY - ECM)
a. Disconnect the T9 ECU connector.
b. Disconnect the E2 ECM connector.
c. Measure the resistance of the wire harness side connectors.