Engine Immobilizer: Overview Lexus SC II рестайлинг

SYSTEM DESCRIPTION

1. ENGINE IMMOBILISER SYSTEM DESCRIPTION The engine immobiliser 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 FUNCTION OF MAIN COMPONENT Component Outline Transponder key coil/amplifier When 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 switch Detects 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 judgment of whether or not to immobilize engine is made. Security indicator light Illuminated or starts flashing. Illumination is controlled by theft warning ECU.
3. SYSTEM FUNCTION When the transponder key ECU detects that the unlock warning switch is ON, the ECU provides current to the transponder key coil and produces a faint electric wave. Upon receiving the electric wave, the transponder chip outputs a key ID code signal. The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ECU The ECU matches the key's ID code with the vehicle's ID code, which is previously registered in the ECU, and then communicates the results to the ECM. After the identification results show that the key's ID code matches the vehicle's ID code and the ECU has confirmed their match: 1) the engine immobiliser system does not immobilize the engine and the engine starting controls (fuel injection control and ignition control) enter standby mode; 2) the ECU transmits a security indicator light signal to the theft warning ECU to turn off the security indicator light.

DESCRIPTION

This DTC will be output if the transponder key ECU does not detect that the unlock warning switch is ON even when the key is inserted into the ignition key cylinder. Under normal conditions, the unlock warning switch is ON when the key is inserted into the ignition key cylinder.

DTC DETECTION CONDITION CHART

Push Switch/Key Unlock Warning Switch Malfunction - Wiring Diagram. Scheme 1

Scheme 2

Scheme 3

1. READ VALUE OF INTELLIGENT TESTER (UNLOCK WARNING SWITCH) Check the DATA LIST for proper functioning of the unlock warning switch. Transponder key ECU: ITEM MEASUREMENT NORMAL CONDITION CHART Item Measurement Item / Display (Range) Normal Condition Diagnostic Note KEY SW Unlock warning switch signal / ON or OFF ON: Key is in ignition key cylinder OFF: No key is in ignition key cylinder - OK: ON (key is in ignition key cylinder) appears on the screen. OK: REPLACE TRANSPONDER KEY ECU NG: Go to next step
2. INSPECT UNLOCK WARNING SWITCH ASSEMBLY (Scheme 2): Inspecting Unlock Warning Switch Assembly Remove the switch. Measure the resistance of the switch. Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Condition Specified Condition 1 - 2 Pushed Below 1 ohms Not pushed 10 kohms or higher NG: REPLACE UNLOCK WARNING SWITCH ASSEMBLY OK: Go to next step
3. CHECK WIRE HARNESS (UNLOCK WARNING SWITCH - TRANSPONDER KEY ECU) Disconnect the U1 switch connector. Disconnect the T13 ECU connector. (Scheme 3): Disconnecting T13 ECU Connector Measure the resistance of the wire harness side connectors. Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition U1-2 (UN+) - T13-3 (KSW) Below 1 ohms U1-1 (UN-) - Body ground U1-2 (UN+) or T13-3 (KSW) - Body ground 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE TRANSPONDER KEY ECU

This DTC is output when: 1) during key code registration, a key malfunction occurs; or 2) the key code was unable to be registered properly.

DTC DETECTION CONDITION CHART

This DTC is output when a key with an incomplete key code is inserted into the ignition key cylinder.

DTC DETECTION CONDITION CHART

This DTC is output when a key with a key code that has not been registered in the transponder key ECU is inserted into the ignition key cylinder.

DTC DETECTION CONDITION CHART

When a key is inserted into the ignition key cylinder but no communication occurs between the key and transponder key ECU, DTC B2796 is output.

When a key is inserted into the ignition key cylinder but a communication error occurs between the key and transponder key ECU, DTC B2798 is output.

DTC DETECTION CONDITION CHART

No Communication In Immobilizer System - Wiring Diagram. Scheme 4

Scheme 5

1. READ VALUE OF INTELLIGENT TESTER (IMMOBILISER SYSTEM) Check the DATA LIST for proper functioning of the engine immobiliser system. Transponder key ECU: ITEM MEASUREMENT NORMAL CONDITION CHART Item Measurement Item / Display (Range) Normal Condition Diagnostic Note IMMOBILISER Immobiliser system status / SET or UNSET SET: No key is in ignition key cylinder UNSET: Ignition switch ON - OK: UNSET (ignition switch ON) appears on the screen. OK: Go to step 3 NG: Go to next step
2. CHECK KEY (OPERATION) Temporarily replace the key with a new or normally functioning one. Check that the engine starts. OK: Engine starts. OK: END (KEY IS DEFECTIVE) NG: Go to next step
3. CHECK WIRE HARNESS (TRANSPONDER KEY AMPLIFIER - TRANSPONDER KEY ECU) Disconnect the T12 amplifier connector. Disconnect the T13 ECU connector. Measure the resistance of the wire harness side connectors. Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition T12-1 (+B) - T13-9 (VC12) Below 1 ohms T12-2 (CODE) - T13-10 (CODE) T12-3 (RXCK) - T13-11 (RXCK) T12-4 (TXCT) - T13-12 (TXCT) T12-5 (GND) - T13-13 (AGND) T12-1 (+B) or T13-8 (VC5) - Body ground 10 kohms or higher T13-10 (CODE) or T12-2 (CODE) - Body ground T12-3 (RXCK) or T13-11 (RXCK) - Body ground T12-4 (TXCT) or T13-12 (TXCT) - Body ground T12-5 (GND) or T13-13 (ANGD) - Body ground (Scheme 5): Disconnecting T13 ECU Connector NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
4. CHECK TRANSPONDER KEY AMPLIFIER (OPERATION) Temporarily replace the transponder key amplifier with a new or normally functioning one. Check that the engine starts. OK: Engine starts. NG: REPLACE TRANSPONDER KEY ECU OK: END (TRANSPONDER KEY AMPLIFIER IS DEFECTIVE)

This DTC is output when a communication error occurs between the transponder key amplifier and transponder key ECU. A possible reason for the communication error is that noise is occurring in the communication line.

DTC DETECTION CONDITION CHART

Communication Malfunction No. 1 - Wiring Diagram. Scheme 6

Scheme 7

Scheme 8

Scheme 9

1. CHECK KEY Check if the ignition key being used is near other ignition keys, as shown in the illustration. Also, check if the key ring is in contact with the key grip. (Scheme 7): Identifying Key Result: RESULT REFERENCE CHART Result Proceed to Key is near other keys and / or key ring is in contact with key grip A Key is not near other keys and / or key ring is not in contact with key grip B B: Go to step 3 A: Go to next step
2. CHECK FOR DTC Separate the keys from each other or remove the key ring. Delete the DTC (see «DTC CHECK / CLEAR» ). Insert a key into the ignition key cylinder. Then remove it. Repeat for all the other keys. Check that no code is output. OK: No code is output. OK: END NG: Go to next step
3. CHECK TRANSPONDER KEY AMPLIFIER Using an oscilloscope or the intelligent tester, check for noise in the waveform between the terminals of the T12 amplifier connector and T13 ECU connector. (Scheme 8): Identifying T12 Transponder Key Amplifier ECU Connector Terminals OK: No noise is present (see illustration). TESTER CONNECTION SPECIFIED CONDITION Tester Connection Tool Setting Condition Specified Condition T12-2 (CODE) -T13-10 (CODE) 5 V/DIV., 50 msec./DIV. Ignition switch ON No noise is present NG: FIND CAUSE OF NOISE AND REMOVE IT OK: Go to next step
4. CHECK WIRE HARNESS (TRANSPONDER KEY AMPLIFIER - TRANSPONDER KEY ECU) Disconnect the T12 amplifier connector. Disconnect the T13 ECU connector. (Scheme 9): Disconnecting T13 ECU Connector Measure the resistance of the wire harness side connectors. Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition T12-2 (CODE) - T13-10 (CODE) Below 1 ohms T12-2 (CODE) or T13-10 (CODE) - Body ground 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
5. CHECK TRANSPONDER KEY AMPLIFIER (OPERATION) Temporarily replace the transponder key amplifier with a new or normally functioning one. Check that the engine starts. OK: Engine starts. NG: REPLACE TRANSPONDER KEY ECU OK: END (TRANSPONDER KEY AMPLIFIER IS DEFECTIVE)

This DTC is output when one of the following occurs: 1) the ECM detects errors in its own communications with the transponder key ECU; 2) the ECM detects errors in the communication lines; or 3) the ECU communication ID between the transponder key ECU and ECM is different and an engine start is attempted.

DTC DETECTION CONDITION CHART

Engine Immobiliser System Malfunction - Wiring Diagram. Scheme 10

This circuit provides power to operate the transponder key ECU.

Power Source Circuit - Wiring Diagram. Scheme 11

Scheme 12

Scheme 13

1. INSPECT FUSE (D/C CUT, IG2 MAIN, IGN, MPX-B1, IG2) Remove the D/C CUT and IG2 MAIN fuses from the engine room No. 1 relay block. Remove the IGN fuse from the engine room No. 2 relay block. Remove the MPX-B1 and IG2 fuses from the passenger side junction block. Measure the resistance of the fuses. Standard resistance: Below 1 ohms NG: REPLACE FUSE OK: Go to next step
2. INSPECT IG2 RELAY Remove the IG2 relay from the engine room No. 1 relay block. Measure the resistance of the relay. (Scheme 12): Measuring Resistance Of Relay Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition 3 - 5 10 kohms or higher Below 1 ohms (when battery voltage is applied to terminals 1 and 2) NG: REPLACE IG2 RELAY OK: Go to next step
3. CHECK WIRE HARNESS (TRANSPONDER KEY ECU - BATTERY AND BODY GROUND) Disconnect the T13 ECU connector. (Scheme 13): Disconnecting T13 ECU Connector Measure the resistance and voltage of the wire harness side connector. Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Specified Condition T13-14 (GND) - Body ground Below 1 ohms Standard voltage TESTER CONNECTION SPECIFIED CONDITION Tester Connection Condition Specified Condition T13-2 (IG2) - Body ground Ignition switch OFF Below 1 V Ignition switch ON 10 to 14 V T13-1 (CPUB) -Body ground Always NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE TRANSPONDER KEY ECU

Scheme 14

1. INSPECT UNLOCK WARNING SWITCH ASSEMBLY Measure the resistance of the switch. Standard resistance TESTER CONNECTION SPECIFIED CONDITION Tester Connection Condition Specified Condition 1 - 2 Pushed Below 1 ohms Not pushed 10 kohms or higher If the result is not as specified, replace the switch assembly. (Scheme 14): Inspecting Unlock Warning Switch Assembly

See also:
• DIAGNOSTIC TROUBLE CODE CHART