Engine Immobilizer: Overview Lexus LS IV

SYSTEM DESCRIPTION

1. ENGINE IMMOBILIZER SYSTEM DESCRIPTION The engine immobilizer system determines whether or not to disable starting of the SFI system based on a comparison of the key's ID codes and the vehicle's pre-registered code. The engine immobilizer system compares the vehicle certification ECU'S pre-registered ID code with the key-embedded transponder chip's ID code. If the ID codes do not match, the engine immobilizer system activates and the SFI system cannot be started. The certification ECU manages communication with the SFI system, main body ECU (driver side junction block), steering lock ECU and ID code box. When the ID codes of the transponder chip and certification ECU match, the certification ECU authorizes the starting of the SFI system.
2. FUNCTION OF MAIN COMPONENT FUNCTION OF MAIN COMPONENT CHART Component Outline Transponder key coil/amplifier (built into engine switch) Receives key ID code, amplifies ID code and outputs it to certification ECU Indoor electrical key oscillator Transmits key detection signals within detection area in vehicle interior upon receiving transmission request signal from certification ECU. Certification ECU request signal is activated when key is brought into vehicle interior and engine switch is pushed. Door control receiver Receives ID code from key in actuation area and transmits it to certification ECU Security indicator light Illuminates or starts blinking. Illumination is controlled by front multiplex network door ECU.
3. SYSTEM FUNCTION Using entry function When the driver (or passenger) is sitting in the vehicle while carrying the key, and the brake pedal is depressed while the engine switch is pressed, the main body ECU (driver side junction block) recognizes that the engine start operation has occurred and sends a certification request signal to the certification ECU. Upon receipt of the certification request signal, the certification ECU sends a request signal to the indoor electrical key oscillator. Upon receipt of the request signal, the indoor electrical key oscillator sends a request signal to detect if the key is inside the vehicle. When the key receives this request signal, it answers by sending an ID code containing a response code through the glass antenna to the door control receiver. Upon receipt of the ID code, the certification ECU analyzes the code. If the interior certification passes, then the main body ECU (driver side junction block) sends a certification pass response signal. When the main body ECU (driver side junction block) receives this signal, the ACC relay is switched on and the IG1 and IG2 relays are switched on in sequence after 0.025 seconds. At this time, the engine switch indicator illuminates in green. Then the certification ECU checks that the power source mode has been changed and sends a steering lock command signal to the main body ECU (driver side junction block). After receiving this signal, the main body ECU (driver side junction block) supplies power to the steering lock actuator. Then (via the ID code box) the steering lock ECU confirms that the certification ECU is certified and drives the steering actuator's motor until the steering lock is unlocked. After unlocking the steering lock, an unlock completed signal is sent to the certification ECU. Upon receipt of this signal, the certification ECU sends an unset command signal to the ID code box. Once this signal is received, the ID code box confirms that the certification ECU is certified, sends an immobilizer unset command signal to the SFI system and sends a security indicator light off signal to the front multiplex network door ECU LH and RH. Not using the entry function (when battery is depleted, affected by wave noise, etc.) When the driver is sitting in the vehicle while carrying the key and the brake pedal is depressed, the main body ECU (driver side junction block) recognizes that the stop light switch is on and sends a key confirmation request signal to the certification ECU. Upon receipt of this signal, the certification ECU drives the motor of the engine switch's built-in immobilizer amplifier. At this time the engine switch sends an RF wave communication signal to the immobilizer. If the driver holds the key up to the engine switch at this time, the engine switch receives the immobilizer RF wave signal and responds by sending a radio wave signal. When the engine switch receives the radio wave signal from the key, it duplicates the signal and sends an ID code to the certification ECU. Upon receipt of the ID code, the code is analyzed. If the certification passes, a key certification pass response signal is sent to the main body ECU (driver side junction block) while simultaneously sending a sound buzzer request signal to the meter ECU. When the main body ECU (driver side junction block) receives this signal, the ACC relay is switched on and the IG1 and IG2 relays are switched on in sequence after 0.025 seconds. At this time, the engine switch indicator illuminates in green. Then the certification ECU checks that the power source mode has been changed and sends a steering lock command signal to the main body ECU (driver side junction block). After receiving this signal, the main body ECU (driver side junction block) supplies power to the steering lock actuator. Then (via the ID code box) the steering lock ECU confirms that the certification ECU is certified and drives the steering actuator's motor until the steering lock is unlocked. After unlocking the steering lock, an unlock completed signal is sent to the certification ECU. Upon receipt of this signal, the certification ECU sends an unset command signal to the ID code box. Once this signal is received, the ID code box confirms that the certification ECU is certified, sends an immobilizer unset command signal to the SFI system and sends a security indicator light off signal to the front multiplex network door ECU LH and RH.

DESCRIPTION

This DTC is output when there is an open or short malfunction in the transponder key coil (built into engine switch).

DTC DETECTION CONDITION CHART

This DTC is output when the engine switch power source supply line is open or shorted.

DTC DETECTION CONDITION CHART

Scheme 1

Scheme 2

1. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH) Disconnect the L15 ECU connector. Disconnect the L36 switch connector. Measure the resistance according to the value(s) in the table below. Standard resistance TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition L15-30 (VC5) - L36-14 (VC5) Always Below 1 ohms L15-40 (AGND) - L36-8 (AGND) L15-30 (VC5) or L36-14 (VCS) - Body ground Always 10 kohms or higher L15-40 (AGND) or L36-8 (AGND) - Body ground NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. REPLACE ENGINE SWITCH Temporarily replace the engine switch with a new one (see «REMOVAL» ).
3. CHECK FOR DTC Clear the DTC (see «DTC CHECK/CLEAR» ). Recheck for DTC (see «DTC CHECK/CLEAR» ). OK: DTC B278A is not output. NG: REPLACE CERTIFICATION ECU (See «REMOVAL» ) OK: END (ENGINE SWITCH IS DEFECTIVE)

This DTC is output when the ID code box detects an internal malfunction.

DTC DETECTION CONDITION CHART

This DTC is output when one of the following occurs: 1) the ECM detected errors in its own communications with the ID code box; 2) the ECM detects errors in the communication lines; or 3) the ECU communication ID between the ID code box and ECM is different and an engine start is attempted. Before troubleshooting for this DTC, make sure no certification ECU DTCs are present. If present, troubleshoot the certification ECU DTCs first.

DTC DETECTION CONDITION CHART

Scheme 3

Scheme 4

1. CHECK FOR DTC Clear the DTC (see «DTC CHECK/CLEAR» ). Recheck for DTC (see «DTC CHECK/CLEAR» ). OK: DTC B2799 is not output. NG: Go to step 2 OK: USE SIMULATION METHOD TO CHECK (See «HOW TO PROCEED WITH TROUBLESHOOTING» )
2. REREGISTER ECU CODE Reregister the recognition codes in ECUs (see «REGISTRATION» ).
3. CHECK FOR DTC Clear the DTC (see «DTC CHECK/CLEAR» ). Recheck for DTC (see «DTC CHECK/CLEAR» ). OK: DTC B2799 is not output. NG: Go to step 4 OK: END (RECOGNITION CODE IN ECU IS DEFECTIVE)
4. CHECK CONNECTION OF CONNECTOR Turn the engine switch off. Check that the connectors are properly connected to the ECM and the ID code box. OK: Connectors are properly connected. NG: CONNECT CONNECTORS PROPERLY OK: Go to next step
5. CHECK HARNESS AND CONNECTOR (ID CODE BOX - ECM) Disconnect the L32 box connector. Disconnect the A13 ECM connector. Measure the resistance according to the value(s) in the table below. Standard resistance TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition L32-5 (EFII) - A13-30 (IMO) Always Below 1 ohms L32-6(EFIO) - A13-31 (IMI) L32-5 (EFII) or A13-30 (IMO) - Body ground Always 10 kohms or higher L32-6 (EFIO) or A13-31 (IMI) - Body ground NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
6. REPLACE ECM Temporarily replace the ECM with a new one (see «REMOVAL»(/lexus/ls/iv-2006-2012/remont/testing-diagnostics/#engine-control-system) ).
7. REGISTER ECU CODE Register the recognition codes in ECUs (see «REGISTRATION» ).
8. CHECK FOR DTC Clear the DTC (see «DTC CHECK/CLEAR» ). Recheck for DTC (see «DTC CHECK/CLEAR» ). OK: DTC B2799 is not output. NG: REPLACE ID CODE BOX (See «REMOVAL» ) OK: END (ECM IS DEFECTIVE)

If the communication line (EFIO-IMI) to the ID code box is stuck on HI output, the ECM outputs this DTC.

DTC DETECTION CONDITION CHART

Scheme 5

Scheme 6

Scheme 7

Scheme 8

1. CLEAR DTC Clear the DTC (see «DTC CHECK/CLEAR» ).
2. CHECK FOR DTC Recheck for DTC (see «DTC CHECK/CLEAR» ). HINT: If any DTCs other than DTC B279A are output, troubleshoot those DTCs first. Result: RESULT CHART Result Proceed to DTC B279A is output A DTC B279A and other DTCs are output B B: Go to «DIAGNOSTIC TROUBLE CODE CHART» A: Go to next step
3. CHECK HARNESS AND CONNECTOR (ID CODE BOX - ECM) Disconnect the L32 box connector. Disconnect the A13 ECM connector. Measure the resistance and voltage according to the value(s) in the table below. Standard resistance TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition L32-6 (EFIO) - A13-31 (IMI) Always Below 1 ohms L32-6 (EFIO) or A13-31 (IMI) - Body ground Always 10 kohms or higher Standard voltage TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition L32-6 (EFIO) - Body ground Always Below 1 V A13-31 (IMI) - Body ground NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
4. CHECK ECM (INPUT) Measure the waveform. Waveform 1 (Reference): WAVEFORM REFERRENCE CHART Item Content Terminal No. (Symbols) A13-31 (IMI) - E3-1 (E1) Tool Setting 10 V/DIV., 100 msec./DIV. Condition Engine switch on (IG) OK: Waveform is output normally ( (Scheme 7)illustration). NG: Go to step 5 OK: REPLACE ID CODE BOX (See «REMOVAL» )
5. CHECK ID CODE BOX (POWER SOURCE AND BODY GROUND) Turn engine switch on (IG). Measure the voltage according to the value(s) in the table below. Standard voltage TESTER CONNECTOR SPECIFIED CONDITION CHART Tester Connector Condition Specified Condition L32-1 (+B) - L32-8 (GND) Always 11 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE ECM (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/testing-diagnostics/#engine-control-system) )

If an ECM that is incompatible with the engine immobilizer system is installed, the ECM outputs this DTC.

DTC DETECTION CONDITION CHART

This circuit provides power to operate the ID code box.

Scheme 9

Scheme 10

1. INSPECT FUSE (SECURITY) Remove the SECURITY fuse from the main body ECU. Measure the resistance according to the value(s) in the table below. Standard resistance TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition SECURITY fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (ID CODE BOX - BATTERY AND BODY GROUND) Disconnect the L32 box connector. Measure the resistance and voltage according to the value(s) in the table below. Standard resistance TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition L32-8 (GND) - Body ground Always Below 1 ohms Standard voltage TESTER CONNECTION SPECIFIED CONDITION CHART Tester Connection Condition Specified Condition L32-1 (+B) - Body ground Always 11 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE (See «PROBLEM SYMPTOMS TABLE» )

See also:
• DIAGNOSTIC TROUBLE CODE CHART
• DIAGNOSIS SYSTEM
• AIRBAG SYSTEM