Fig. 2: Identifying Engine Immobilizer System Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
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. 41: Identifying T9 And T8 Amplifier Connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
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
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
WIRING DIAGRAM
Tester connectionSpecified condition
T9-10 (CODE) - T8-4 (CODE)Below 1 ohms
