Four Wheel Drive Control System (Diagnostics - Introduction): Other Lexus GS III facelift

TERMINALS OF ECU

HINT

Inspect the connector from the back side while connector is connected.

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1. 4WD CONTROL ECU: Symbols (Terminal No.) Wiring Color Terminal Description Condition Specified Condition CANH (U52-1) - CANL (U52-14) W-B CAN communication line Engine switch off 54 to 67 ohms RRO (U52-2) - GND (U52-30) P - W-B Rear right wheel speed sensor signal Engine switch on (IG), driving at approximately 18 mph (30 km/h) Pulse generation (see waveform 1 in (Scheme 134) ) FRO (U52-3) - GND (U52-30) G - W-B Front right wheel speed sensor signal Engine switch on (IG), driving at approximately 18 mph (30 km/h) Pulse generation (see waveform 1 in (Scheme 134) ) IG1 (U52-9) - GND (U52-30) B - W-B Power source voltage Engine switch on (IG) 10 to 14 V SLC+ (U52-13) - SLC- (U52-32) V - O Transfer control solenoid signal Engine switch on (IG) Pulse generation (see waveform 2 in (Scheme 135) ) RLO (U52-15) - GND (U52-30) L - W-B Rear left wheel speed sensor signal Engine switch on (IG), driving at approximately 18 mph (30 km/h) Pulse generation (see waveform 1 in (Scheme 134) ) FLO (U52-16) - GND (U52-30) R - W-B Front left wheel speed sensor signal Engine switch on (IG), driving at approximately 18 mph (30 km/h) Pulse generation (see waveform 1 in (Scheme 134) ) FREE (U52-23) - GND (U52-30) GR - W-B Sets the center differential free Engine switch on (IG), open and short terminals OPA and CG of the DLC3. 10 to 14 V --> 0 to 1.5 V GND (U52-30) - Body ground W-B - Body ground Ground Always Below 1 ohms Waveform 1 (Reference): Item Contents Tool setting 2 V/DIV, 2 ms/DIV Vehicle condition Driving at approximately 18 mph (30 km/h) HINT: As vehicle speed (wheel rotation speed) increases, the width of the waveform narrows. Waveform 2 (Reference): Item Contents Tool setting 5 V/DIV, 2 ms/DIV Vehicle condition Engine stop, Engine switch on (IG)

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1. DIAGNOSIS SYSTEM Inspect the battery voltage. Voltage 11 to 14 V If the voltage is below 11 V, recharge the battery before proceeding. Check the DLC3. The 4WD control ECU uses CAN and the ISO 9141-2 for communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format. Verify the conditions listed in the table below. Symbols (Terminal No.) Terminal Description Condition Specified condition SIL (7) - SG (5) Bus "+" line During transmission Pulse generation CG (4) - Body ground Chassis ground Always Below 1 ohms SG (5) - Body ground Signal ground Always Below 1 ohms BAT (16) - Body ground Battery positive Always 11 to 14 V CANH (6) - CANL (14) HIGH-level CAN bus line Engine switch off 54 to 67 ohms CANH (6) - Battery positive HIGH-level CAN bus line Engine switch off 1 Mohms or higher CANH (6) - CG (4) HIGH-level CAN bus line Engine switch off 3 kohms or higher CANL (14) - Battery positive LOW-level CAN bus line Engine switch off 1 Mohms or higher CANL (14) - CG (4) LOW-level CAN bus line Engine switch off 3 kohms or higher HINT: If the display shows a communication error message when the cable of the Techstream is connected to the DLC3, the engine switch is turned on (IG) and the Techstream is operated, there is a problem on either the vehicle side or the tester side. If communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle. If communication is still not possible when the tester is connected to another vehicle, the problem is probably in the tester itself. Consult the Service Department listed in the tester's operator's manual.
2. FUNCTION OF 4WD INDICATOR LIGHT The 4WD indicator light in the combination meter assembly (multi-information display) warns the driver of abnormal or poor condition of the four wheel drive control system.
3. CHECK MASTER CAUTION INDICATOR Turn the engine switch on (IG), and check that the master caution indicator comes on for approximately 3 seconds. HINT: The master caution indicator goes off while the system is in the DTC output mode and blinks while other systems are in the Test Mode.
4. CHECK 4WD INDICATOR LIGHT Using SST, connect terminals TC and CG of the DLC3 (to be in the DTC output mode). SST: 09843-18040 Turn the engine switch on (IG). "DIAG" is displayed on the multi-information display, and the 4WD control ECU checks the system for malfunctions. If the 4WD control system is normal, "DIAG 4WD OK" will be displayed on the multi-information display. If the 4WD control system is not normal, "DIAG 4WD XX(DTC)" will be displayed on the multi-information display. Although the Test Mode is not set for the 4WD control system, a message on the left will be displayed on the multi-information display when the Test Mode is activated for checking the VSC, etc. HINT: Test Mode DTCs will not be stored because the Test Mode is not set. On the multi-information display, VSC, TIRE PRESSURE and 4WD are displayed in order. If the systems above are not displayed on the multi-information display, there may be a malfunction in "TC and CG Terminal Circuit". Refer to «TC and CG Terminal Circuit»(ref-382789-S29254311532011012800000) . If the 4WD indicator light check result is not normal, proceed to troubleshooting for the 4WD indicator light circuit. Trouble Area See procedure 4WD indicator light (Remains on) Refer to «4WD Indicator Light Remains ON»(ref-382789-S17408765812011012800000) 4WD indicator light (Does not come on) Refer to «4WD Indicator Light does not Come ON»(ref-382789-S21938993872011012800000)
5. FAIL-SAFE FUNCTION If following malfunctions occur, the 4WD control ECU will stop the function of 4WD control system or partly change the function to control the system. Malfunction Control Malfunction in a speed sensor Stop the function Malfunction in the steering angle sensor and throttle signal line Partly change the function