Cruise Control: Overview Lexus LS IV

SYSTEM DESCRIPTION

1. CRUISE CONTROL SYSTEM This system is controlled by the ECM, and is activated by the throttle position sensor and motor. The ECM controls the following functions: ON-OFF, -/SET, +/RES, CANCEL vehicle speed operation, motor output control, and overdrive control. The ECM compares the driving vehicle speed from the skid control ECU with the stored vehicle speed set through the cruise control switch. The ECM controls the throttle motor of the throttle body to close the valve when the driving speed is less than the stored speed. The ECM receives signals such as ON-OFF, -/SET, +/ RES, and CANCEL from the cruise control switch. The ECM illuminates the combination meter CRUISE indicator light when it receives the cruise control switch ON signal. The ECM cancels the cruise control system when the brake pedal is depressed and the ECM receives the stop light switch signal. The ECM cancels the cruise control system when it detects that the shift position is changed from D (8th, 7th, 6th, 5th or 4th gear) to N (3rd, 2nd, 1st gear), based on the park/neutral position switch signal.
2. LIMIT CONTROL Low speed limit: The lowest possible limit of the speed setting range is set at approximately 40 km/h (25 mph). The cruise control system cannot be set when the driving vehicle speed is below the low speed limit. Cruise control operation will be automatically canceled and the set speed is stored in memory when the vehicle speed decreases below the low speed limit 40 km/h (25 mph) while the cruise control is operating. High speed limit: The highest possible limit of the speed setting range is set at approximately 200 km/h (125 mph). The cruise control system cannot be set when the driving vehicle speed is over the high speed limit. Also, +/RES cannot be used to increase speed beyond the high speed limit.
3. OPERATION OF CRUISE CONTROL The cruise control switch operates 7 functions: SET, COAST, TAP-DOWN, RESUME, ACCELERATION (ACCEL), TAP-UP, and CANCEL. The SET, TAP-DOWN and COAST functions, and the RESUME, TAP-UP and ACCEL functions are operated with the same switch. The cruise control switch is an automatic return type switch which turns on only while operating it in each arrow direction and turns off after releasing it. SET CONTROL Vehicle speed is stored and constant speed control is maintained when pushing the switch to -/SET while driving with the cruise control switch ON (the CRUISE main indicator light is illuminated), and the vehicle speed is within the set speed range (between the low and high speed limits). COAST CONTROL The ECM changes the cruise control demanding throttle opening angle to 0° and decelerates the vehicle when -/SET on the cruise control switch is pressed and held while the cruise control system is operating. When the cruise control switch is released from -/SET, the vehicle speed is stored and constant speed control is maintained. HINT: The throttle valve is not fully closed due to idle speed control, etc. TAP-DOWN CONTROL When tapping down the cruise control switch to -/ SET (for approximately 0.5 seconds) while the cruise control system is in operation, the stored vehicle speed decreases each time by approximately 1.6 km/h (1.0 mph). When the cruise control switch is released from -/SET and the difference between the driving and stored vehicle speed is more than 5 km/h (3 mph), the vehicle speed is stored and constant speed control is maintained. ACCEL CONTROL The throttle valve motor of the throttle position sensor and motor is instructed by the ECM to open the throttle valve when +/RES on the cruise control switch is pressed and held while the cruise control system is operating. When the cruise control switch is released from +/RES, the vehicle speed is stored and constant speed is maintained. TAP-UP CONTROL When tapping up the cruise control switch to +/RES (for approximately 0.5 seconds) while the cruise control system is in operation, the stored vehicle speed increases each time by approximately 1.6 km/h (1.0 mph). However, when the difference between the driving and the stored vehicle speed is more than 5 km/h (3 mph), the stored vehicle speed will not be changed. RESUME CONTROL If the cruise control operation was canceled with the stop light switch or CANCEL switch, and if driving speed is within the limit range, pushing the cruise control switch to +/RES restores vehicle speed memorized at the time of cancellation, and maintains constant speed mode. OVERDRIVE CONTROL Overdrive may cancel automatically when using cruise control while driving on inclined roads, etc. After overdrive is canceled, if the system determines that the road is no longer inclined based on throttle opening information, overdrive will be restored. If overdrive was canceled during ACCEL or RESUME operation, overdrive will be restored after the ACCEL or RESUME operation is completed. CANCEL CONTROL Manual cancel Performing any of the following cancels the cruise control system (the stored vehicle speed in the ECM is maintained). Depressing the brake pedal Pushing the cruise control switch to CANCEL Turning the cruise control switch OFF (set speed is not stored in memory). Moving the shift lever to any position except D (8th, 7th, 6th, 5th or 4th gear)
4. AUTO CANCEL (FAIL-SAFE) This system has an automatic cancellation function (see «FAIL-SAFE CHART» ).

DESCRIPTION

When the ECM receives electronically controlled brake system malfunctioning signal from the skid control ECU via the CAN communication line, DTC C1A50 is output.

DIAGNOSTIC TROUBLE CODE CHART

When the brake pedal is depressed, the stop light switch sends a signal to the ECM.

Receiving the signal, the ECM cancels the cruise control system. Even if there is a malfunction in the stop light signal circuit while the cruise control is in operation, normal driving is maintained due to a fail-safe function. Cruise control is canceled when positive battery voltage is applied to terminal STP.

When the brake pedal is depressed, positive voltage is applied to terminal STP of the ECM through the STOP fuse and the stop light switch, and the ECM cancels the cruise control.

When the brake pedal is released, positive voltage is applied to terminal ST1- of the ECM through the ECU-IG fuse and the stop light switch, and the ECM operates the cruise control.

DIAGNOSTIC TROUBLE CODE CHART

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1. READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH) Check the Data List for proper functioning of the stop light switch. Cruise Control CRUISE CONTROL REFERENCE CHART Tester Display Measurement Item/Range Normal Condition Diagnostic Note Stop Light SW M-CPU Stop light switch signal (Main CPU)/ON or OFF OK: Brake pedal is depressed OFF: Brake pedal is released - OK: Display changes according to brake pedal operation described in the above table. NG: Go to step 2 OK: REPLACE ECM (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/testing-diagnostics/#engine-control-system) )
2. INSPECT FUSE (STOP, ECU-IG) Remove the STOP fuse from the main body ECU. Remove the ECU-IG fuse from the engine room No. 2 junction block. Measure the resistance of the fuses. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Switch Condition STOP fuse Always Below 1 ohms ECU-IG fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
3. INSPECT STOP LIGHT SWITCH ASSEMBLY Remove the stop light switch (see «STOP LIGHT SWITCH» ). Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Switch Condition Specified Condition 1 - 2 Pushed Below 1 ohms 1 - 2 Not pushed 10 kohms or higher 3 - 4 Not pushed Below 1 ohms 3 - 4 Pushed 10 kohms or higher NG: REPLACE STOP LIGHT SWITCH ASSEMBLY (See «REMOVAL» ) OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (ECM - BATTERY) Disconnect the A14 ECM connector. Measure the voltage according to the value(s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition A14-12 (ST1-) - Body ground Brake pedal is depressed 11 to 14 V A14-12 (ST1-) - Body ground Brake pedal is released Below 1 V A14-13 (STP) - Body ground Brake pedal is released 11 to 14 V A14-13 (STP) - Body ground Brake pedal is depressed Below 1 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE ECM (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/testing-diagnostics/#engine-control-system) )

This DTC indicates the internal abnormalities of the ECM.

DTC DETECTION CONDITION CHART

HINT

If DTC P0575 is detected while the cruise control is in operation, the skid control ECU clears the stored vehicle speed in the ECM and cancels the cruise control operation. At the same time, the CRUISE main indicator light blinks to inform the driver of the malfunction. When this trouble code is detected, fail-safe remains on until the engine switch is turned off.

Send vehicle speed signal to skid control ECU, and then it is sent to ECM.

DTC DETECTION CONDITION CHART

This circuit sends a signal to the ECM depending on the cruise control main switch condition. The battery supplies positive (+) battery voltage to the circuit control switch. Then terminal CCS of the ECM receives the voltage according to the switch condition.

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1. READ VALUE USING TECHSTREAM (CRUISE CONTROL MAIN SWITCH) Check the Data List for proper functioning of the cruise control main switch. Cruise Control CRUISE CONTROL REFERENCE CHART Tester Display Measurement Item/Range Normal Condition Diagnostic Note CCS Main SW M-CPU Cruise control switch signal (Main CPU)/ON or OFF ON: Cruise control switch is ON OFF: Cruise control switch is OFF - Cancel Switch Cancel switch signal/ON or OFF ON: CANCEL switch is ON OFF: CANCEL switch is OFF - SET/COAT Switch -/SET switch signal/ON or OFF ON: -/SET switch is ON OFF: -/SET switch is OFF - RES/ACC Switch +/RES switch signal/ON or OFF ON: +/RES switch is ON OFF: +/RES switch is OFF - OK: When cruise control main switch operation is performed, the results are the same as above. NG: Go to step 2 OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE (See «PROBLEM SYMPTOMS TABLE» )
2. INSPECT CRUISE CONTROL SWITCH Remove the cruise control switch. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Switch Condition Specified Condition 1 - 3 Cruise control switch ON Below 1 ohms 1 - 3 Cruise control switch OFF 10 kohms or higher 1 - 3 +/RES switch hold ON 235 to 245 ohms 1 - 3 -/SET switch hold ON 620 to 640 ohms 1 - 3 CANCEL switch hold ON 1510 to 1570 ohms NG: REPLACE CRUISE CONTROL SWITCH (See «REMOVAL» ) OK: Go to next step
3. INSPECT SPIRAL CABLE SUB-ASSEMBLY Disconnect the z2 cruise control switch wire connector. Disconnect the L24 cable connector. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition z2-3 - L24-1 (CCS) Always Below 3 ohms z2-4 - L24-2 (ECC) Always Below 3 ohms z2-3 - Body ground Always 10 kohms or higher z2-4 - Body ground Always 10 kohms or higher NG: REPLACE SPIRAL CABLE SUB-ASSEMBLY (See «REMOVAL» ) OK: Go to next step
4. INSPECT CRUISE CONTROL SWITCH WIRE Disconnect the z2 spiral cable connector. Disconnect the A cruise control switch connector. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition z2-3 - A-3 Always Below 1 ohms z2-4-A-1 Always Below 1 ohms A-3 - Body ground Always 10 kohms or higher A-1 - Body ground Always 10 kohms or higher NG: REPLACE CRUISE CONTROL SWITCH WIRE OK: Go to next step
5. CHECK HARNESS AND CONNECTOR (SPIRAL CABLE - ECM AND BODY GROUND) Disconnect the L24 cable connector. Disconnect the A13 ECM connector. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition L24-1 (CCS) - A13-15 (CCS) Always Below 1 ohms L24-2 (ECC) - Body ground Always Below 1 ohms L24-1 (CCS) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE ECM (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/testing-diagnostics/#engine-control-system) )

1. When the ECM detects a cruise control main switch signal, it sends it to the combination meter through CAN communication. Then the CRUISE main indicator light turns on.
2. The CRUISE main indicator light circuit uses CAN communication. If there is a malfunction in this circuit, check for DTCs in the CAN communication system before troubleshooting this circuit.

The driving support ECU uses the front millimeter wave radar sensor to detect obstacles in front of the vehicle and the direction that the driver's head is facing.

DTC DETECTION CONDITION CHART

When the driving support ECU is replaced with a new one, it acquires the country specification information from the combination meter. When the country specification information in the ECU and meter do not match, DTC C1A02 is output.

DTC DETECTION CONDITION CHART

DTC DETECTION CONDITION CHART

When the brake pedal is depressed, the stop light switch sends signal to the driving support ECU.

Receiving the signal, the driving support ECU cancels the dynamic radar cruise control system. Even if these is a malfunction in the stop light signal circuit while the cruise control is in operation, normal driving is maintained due to fail-safe function. Dynamic radar cruise control is canceled when positive battery voltage is applied to terminal STP-.

When the brake pedal is depressed, positive voltage is applied to terminal STP- of the driving support ECU through the STOP fuse and the stop light switch, and the driving support ECU cancels the cruise control.

When the brake pedal is released, positive voltage is applied to terminal ST1- of the driving support ECU through the ECU-IG fuse and the stop light switch, and the driving support ECU operates the dynamic radar cruise control.

DTC DETECTION CONDITION CHART

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1. READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH) Check the Data List for proper functioning of the stop light switch. Radar Cruise RADAR CRUISE REFERENCE CHART Tester Display Measurement Item/Range Normal Condition Diagnostic Note Stop Light SW 1 M-CPU Stop light switch signal (Main CPU)/ON or OFF OK: Brake pedal is depressed OFF: Brake pedal is released - Stop Light SW 2 M-CPU Stop light switch signal (Main CPU)/ON or OFF OK: Brake pedal is depressed OFF: Brake pedal is released - Stop Light SW 1 S-CPU Stop light switch signal (Sub CPU)/ON or OFF OK: Brake pedal is depressed OFF: Brake pedal is released - OK: Display changes according to brake pedal operation described in above table. NG: Go to step 2 OK: REPLACE DRIVING SUPPORT ECU (See «REMOVAL» )
2. INSPECT FUSE (STOP, ECU-IG) Remove the STOP fuse from the main body ECU. Remove the ECU-IG fuse from the engine room No. 2 junction block. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition STOP fuse Always Below 1 ohms ECU-IG fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
3. INSPECT STOP LIGHT SWITCH ASSEMBLY Remove the stop light switch (see «STOP LIGHT SWITCH» ). Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Switch Condition Specified Condition 1 - 2 Pushed 10 kohms or higher 1 - 2 Not pushed Below 1 ohms 3 - 4 Not pushed Below 1 ohms 3 - 4 Pushed 10 kohms or higher NG: REPLACE STOP LIGHT SWITCH ASSEMBLY (See «STOP LIGHT SWITCH» ) OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (ECU - BATTERY) Disconnect the A33 ECU connector. Measure the voltage according to the value(s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition A33-11 (STP-) - Body ground Brake pedal is depressed Below 1 V A33-11 (STP-) - Body ground Brake pedal is released 11 to 14 V A33-34 (ST1-) - Body ground Engine switch is on (IG), brake pedal is released 11 to 14 V A33-34 (ST1-) - Body ground Engine switch is on (IG), brake pedal is depressed Below 1 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE DRIVING SUPPORT ECU (See «REMOVAL» )

When the front millimeter wave radar sensor is replaced with a new one, it acquires the country specification information from the driving support ECU. Also, when the driving support ECU is replaced with a new one, it receives the country specification information from the combination meter. When the country specification information in the sensor and ECU do not match, DTC C1A0A is output.

DTC DETECTION CONDITION CHART

When the driving support ECU receives information that there is a malfunction in the front millimeter wave radar sensor, DTC C1A10 is output.

DTC DETECTION CONDITION CHART

When the vehicle is determined to be driving in a straight line or on a slow curve based on signals from the yaw rate sensor, etc., the front millimeter wave radar sensor assembly performs a self diagnosis to check if the sensor beam axis is deviated from the vehicle movement direction. When the front millimeter wave radar sensor assembly's beam axis is deviated, the driving support ECU detects this, and outputs DTC C1A11.

After installing a new front millimeter wave radar sensor, if the sensor beam axis adjustment is not performed, DTC C1A14 is output.

DTC DETECTION CONDITION CHART

When the driving support ECU receives an engine control (SFI) system or automatic transmission (ECT) system malfunctioning signal from the ECM via the CAN communication line, DTC C1A40 is output.

DTC DETECTION CONDITION CHART

The skid control ECU receives brake control request signals from the ECM and driving support ECU. When the request signals received from the ECM and driving support ECU are not consistent, the skid control ECU determines that a malfunction has occurred and sends a malfunction signal to the driving support ECU.

DTC DETECTION CONDITION CHART

The driving support ECU sends a sounding signal to the skid control ECU to sound the skid control buzzer.

DTC DETECTION CONDITION CHART

This DTC is output when a communication malfunction occurs between the sensors and ECUs.

DTC DETECTION CONDITION CHART

The cruise control switch operates 8 functions: SET, COAST, TAP-DOWN, RESUME, ACCEL, TAP-UP, CANCEL and MODE. The SET, TAP-DOWN and COAST functions, and the RESUME, TAP-UP and ACCEL functions are operated with the same switch. The cruise control switch is an automatic return type switch which turns on only while operating it in each arrow direction and turns off after releasing it. The internal contact point of the cruise control switch is turned on with the switch operation. The driving support ECU then reads the resistance value that has been changed by the switch operation to control MODE, SET, COAST, RESUME, ACCEL and CANCEL. The dynamic radar cruise control system has two cruise control modes: the constant speed control mode and vehicle-to-vehicle distance control mode.

HINT

1. The vehicle-to-vehicle distance control mode is always selected when starting up the dynamic radar cruise control system.
2. The operation of the constant speed control mode is the same as the cruise control system.

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1. READ VALUE USING TECHSTREAM (CRUISE CONTROL MAIN SWITCH) Check the Data List T for proper functioning of the cruise control switch. Radar Cruise RADAR CRUISE REFERENCE CHART Tester Display Measurement Item/Range Normal Condition Diagnostic Note Cruise Control Main Switch Cruise control switch signal (Main CPU)/ON or OFF ON: Cruise control switch is ON OFF: Cruise control switch is OFF - Cancel Switch Cancel switch signal/ON or OFF ON: CANCEL switch ON OFF: CANCEL switch OFF - SET/COAT Switch -/SET switch signal/ON or OFF ON: -/SET switch ON OFF: -/SET switch OFF - RES/ACC Switch +/RES switch signal/ON or OFF ON: +/RES switch ON OFF: +/RES switch OFF - OK: When cruise control switch operation is performed, the results are same as above. NG: Go to step 2 OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE (See «PROBLEM SYMPTOMS TABLE» )
2. INSPECT CRUISE CONTROL SWITCH Disconnect the cruise control switch connector. Measure the resistance of the switch. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Switch Condition Specified Condition 1 - 3 RES/ACC switch is held ON 235 to 245 ohms 1 - 3 SET/COAST switch is held ON 620 to 640 ohms 1 - 3 CANCEL switch is held ON 1510 to 1570 ohms 1 - 3 Cruise control switch OFF 10 kohms or higher 1 - 3 Cruise control switch ON Below 1 ohms 1 - 2 MODE switch is held ON Below 1 ohms NG: REPLACE CRUISE CONTROL SWITCH (See «REMOVAL» ) OK: Go to next step
3. INSPECT SPIRAL CABLE SUB-ASSEMBLY Disconnect the z2 and L24 spiral cable connectors. Measure the resistance of the spiral cable. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Condition Condition Specified Condition z2-3 - L24-1 (CCS) Always Below 1 ohms z2-1 - L24-7 (R/N) Always Below 1 ohms z2-4 - L24-2 (ECC) Always Below 1 ohms NG: REPLACE SPIRAL CABLE SUB-ASSEMBLY (See «REMOVAL» ) OK: Go to next step
4. INSPECT CRUISE CONTROL SWITCH WIRE Disconnect the z2 spiral cable connector. Disconnect the A cruise control switch connector. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition z2-3 - A-3 Always Below 1 ohms z2-4 - A-1 Always Below 1 ohms z2-1 - A-2 Always Below 1 ohms A-3 - Body ground Always 10 kohms or higher A-1 - Body ground Always 10 kohms or higher A-2 - Body ground Always 10 kohms or higher NG: REPLACE CRUISE CONTROL SWITCH WIRE (See «REMOVAL» ) OK: Go to next step
5. CHECK HARNESS AND CONNECTOR (SPIRAL CABLE - ECU AND BODY GROUND) Disconnect the L24 spiral cable connector. Disconnect the A33 ECU connector. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition L24-1 (CCS) - A33-27 (CCS) Always Below 1 ohms L24-7 (R/N) - A33-30 (CCHG) Always Below 1 ohms L24-2 (ECC) - Body ground Always Below 1 ohms L24-1 (CCS) - Body ground Always 10 kohms or higher L24-7 (R/B) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE DRIVING SUPPORT ECU (See «REMOVAL» )

This circuit provides power to the front millimeter wave radar sensor. The front millimeter wave radar sensor emits radio waves towards an object in front and measures the distance and direction of the object by receiving the beam reflections. Based on the reflections, the sensor calculates the difference in speed between the vehicle and the object in front. This data is transmitted to the driving support ECU.

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1. CHECK HARNESS AND CONNECTOR (FRONT MILLIMETER WAVE RADAR SENSOR - DRIVING SUPPORT ECU) Disconnect the B9 sensor connector. Disconnect the A33 ECU connector. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition B9-2 (SGND) - A33-26 (SGND) Always Below 1 ohms B9-5 (IGB) - A33-36 (IGB) Always Below 1 ohms B9-2 (SGND) - Body ground Always 10 kohms or higher B9-5 (IGB) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. CHECK DRIVING SUPPORT ECU (IGB VOLTAGE SIGNAL) Measure the voltage according to the value(s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition B9-5 (IGB) - B9-2 (SGND) Engine switch on (IG) 11 to 14 V NG: REPLACE DRIVING SUPPORT ECU (See «REMOVAL» ) OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE (See «PROBLEM SYMPTOMS TABLE» )

The distance control switch sets the vehicle-to-vehicle distance mode. The distance control switch is installed in the steering pad switch with modulator (distance control switch). The vehicle-to-vehicle distance set value can be changed by operating the steering pad switch while the dynamic radar cruise control system is in operation. The steering pad switch with modulator uses the CAN communication line to communicate with each ECU.

When the cruise control main switch is on, the CRUISE main indicator light and RADAR READY indicator turn on. These lights indicate the control condition (presence or absence of a vehicle in front, vehicle-to-vehicle distance, and set vehicle speed) and fail-safe state through the CAN communication system. The master warning light and CRUISE main indicator light turn on and vehicle-to-vehicle distance information is displayed on the combination meter as the alarm buzzer sounds. Items such as "Clean Radar Sensor", "Cruise not Available", "Check Cruise Control System" and "Radar Ready" are displayed in the multi-information display on the combination meter when the driving support ECU detects signals from each sensor and actuator and sends them to the combination meter via CAN.

HINT

1. If the vehicle in front in the same lane significantly decreases vehicle speed or another vehicle moves in front of your vehicle, adequate deceleration cannot be applied and the vehicle-to-vehicle distance will shorten. At this time, the system sounds the buzzer and the master warning light blinks to warn the driver.
2. Each indicator in the dynamic radar cruise control uses CAN communication. Therefore if there are any malfunctions in this circuit, check for DTCs in the CAN communication system before troubleshooting this circuit.

This circuit provides power to operate the driving support ECU.

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1. CHECK FUSE (D-IG1-2) Remove the D-IG1-2 fuse from the main body ECU. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition D-IG1-2 fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (DRIVING SUPPORT ECU - BATTERY AND BODY GROUND) Disconnect the A33 ECU connector. Measure the voltage according to the value(s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Condition Specified Condition A33-13 (B) - Body ground Engine switch on (IG) 11 to 14 V A33-13 (B) - Body ground Engine switch off Below 1 V Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A33-25 (GND) - Body ground Always Below 1 ohms NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE (See «PROBLEM SYMPTOMS TABLE» )

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1. REMOVE COWL TOP VENTILATOR LOUVER LH (See «REMOVAL» )
2. DISCONNECT CABLE FROM NEGATIVE BATTERY TERMINAL CAUTION: Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to prevent airbag and seat belt pretensioner activation. NOTE: After the engine switch is turned off, the HDD navigation system requires approximately 6 minutes to record various types of memory and settings. As a result, after turning the engine switch off, wait 6 minutes or more before disconnecting the cable from the negative (-) battery terminal.
3. REMOVE SWITCH AND VOLUME CASE (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) )
4. REMOVE NO. 2 STEERING WHEEL COVER LOWER (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) )
5. REMOVE STEERING PAD (See «REMOVAL»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) )
6. REMOVE CRUISE CONTROL MAIN SWITCH ASSEMBLY Disconnect the connector and clamp. Remove the 2 screws. Remove the switch.

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1. INSPECT CRUISE CONTROL MAIN SWITCH ASSEMBLY Measure resistance (Vehicle without vehicle-to-vehicle distance control mode) Remove the cruise control main switch. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Switch Condition Specified Condition 4 (ECC) - 3 (CCS) Neutral 1 Mohms or higher 4 (ECC) - 3 (CCS) +RES 235 to 245 ohms 4 (ECC) - 3 (CCS) -SET 617 to 643 ohms 4 (ECC) - 3 (CCS) CANCEL 1509 to 1571 ohms 4 (ECC) - 3 (CCS) Main Switch OFF 1 Mohms or higher 4 (ECC) - 3 (CCS) Main Switch ON Below 2.5 ohms If the result is not as specified, replace the cruise control main switch. Measure resistance (Vehicle with vehicle-to-vehicle distance control mode) Remove the cruise control main switch. Measure the resistance according to the value(s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Switch Condition Specified Condition 4 (ECC) -1 (R/N) 4 (ECC) - 3 (CCS) Neutral 1 Mohms or higher 4 (ECC) - 3 (CCS) +RES 235 to 245 ohms 4 (ECC) - 3 (CCS) -SET 617 to 643 ohms 4 (ECC) - 3 (CCS) CANCEL 1509 to 1571 ohms 4 (ECC) - 3 (CCS) Main Switch OFF 1 Mohms or higher 4 (ECC) - 3 (CCS) Main Switch ON Below 2.5 ohms 3 (CCS) -1 (R/N) Main Switch on and Mode Switch ON Below 2.5 ohms If the result is not as specified, replace the cruise control main switch.

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1. INSTALL CRUISE CONTROL MAIN SWITCH ASSEMBLY Install the switch. Install the 2 screws. Connect the connector and clamp.
2. INSTALL STEERING PAD (See «INSTALLATION»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) )
3. INSTALL SWITCH AND VOLUME CASE (See «INSTALLATION»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) )
4. INSTALL NO. 2 STEERING WHEEL COVER LOWER (See «INSTALLATION»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) )
5. CONNECT CABLE TO NEGATIVE BATTERY TERMINAL
6. REMOVE COWL TOP VENTILATOR LOUVER LH (See «INSTALLATION» )
7. PERFORM INITIALIZATION Perform initialization (see «INITIALIZATION» ). NOTE: Certain systems need to be initialized after disconnecting and reconnecting the cable from the negative (-) battery terminal.
8. CHECK SRS WARNING LIGHT Check the SRS warning light (see «DIAGNOSIS SYSTEM»(/lexus/ls/iv-2006-2012/remont/airbag/#supplemental-restraint-system) ).

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See also:
• DIAGNOSTIC TROUBLE CODE CHART
• REMOVAL
• REMOVAL
• INSPECTION
• REMOVAL
• REMOVAL