Pre-Collision System (Diagnostics - Introduction): Other Lexus GS IV

PRECAUTION [03/2012 - ]

1. PRECAUTIONS FOR TROUBLESHOOTING If the malfunction is due to connectors being loosely connected, or improper installation of parts, reconnecting the connectors or removing and reinstalling the parts may temporarily or completely correct the problem. To determine the malfunctioning area, use DTCs, freeze frame data and other data to help determine conditions at the time of the malfunction. Write down the data before disconnecting connectors or removing and installing parts. The pre-collision system may be affected by malfunctions in other systems. Check for DTCs in other systems and, if present, troubleshoot those DTCs first.
2. SERVICE PRECAUTIONS For parts that do not have specific inspection methods, perform all removal and installation procedures with the power switch off. After removal and installation of parts has been performed, check for DTCs and confirm that none are output.
3. PRECAUTIONS WHEN REPLACING DRIVING SUPPORT ECU If the driving support ECU has been replaced, turn the power switch off --> on (IG) for 10 seconds --> off to perform the initialization.

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COMMUNICATION TABLE

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1. PRE-COLLISION SYSTEM DESCRIPTION The pre-collision system detects vehicles and obstacles in front of the vehicle and performs the following: 1) optimally uses system controls to avoid collisions, and 2) uses system controls to reduce impact during a collision.
2. PRE-COLLISION DETECTION OUTLINE Front collision detection The driving support ECU receives information about vehicles and obstacles in front of the vehicle from the millimeter wave radar sensor assembly. Then, based on vehicle speed, road conditions and obstacle location, the driving support ECU determines, in advance, the risk of a crash and if a crash is unavoidable. The driver monitor camera detects the direction that the driver's head is facing and whether the driver's eyes are open or closed. When a potential crash is detected and the camera determines that the driver's head is not facing forward or that the driver's eyes are closed, it activates the pre-collision safety controls in advance. Sudden braking detection The skid control ECU assembly activates the pre-collision seat belts when it detects sudden braking. Sudden braking is determined based on brake oil pressure and other information from the master cylinder pressure sensor. Vehicle control impossible judgment The pre-collision seat belts are activated when it is determined that the vehicle cannot be controlled. The judgment is based on vehicle stability information from the yaw rate sensor and steering angle sensor. Component Component Detection Content Millimeter wave radar sensor assembly Front object Skid control ECU assembly Sudden braking or vehicle control is not possible Driver monitor camera Driver facial direction Driver eye opening level signal
3. PRE-COLLISION SYSTEM CONTROL DESCRIPTION Operation Condition Controls Sender ECU Receiver ECU Part Operated Front collision detection Collision is possible Pre-collision alarm Driving support ECU Combination meter assembly Skid control ECU assembly Combination meter assembly Skid control ECU assembly Collision is unavoidable Pre-collision seat belts Driving support ECU Seat belt control ECU Front seat outer belts Collision is possible Collision is unavoidable Pre-collision brake assist Pre-collision brake Driving support ECU Skid control ECU assembly Brake assist system Collision is possible Collision is unavoidable Suspension control Driving support ECU Absorber control ECU Shock absorber Sudden braking detected Pre-collision seat belts Skid control ECU assembly Seat belt control ECU Front seat outer belts Vehicle control impossible judgment Pre-collision seat belts Skid control ECU assembly Seat belt control ECU Front seat outer belts
4. PRE-COLLISION ALARM CONTROL When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, the multi-information display and warning buzzer are used to warn the driver and help with collision avoidance.
5. PRE-COLLISION SEAT BELT CONTROL When the system determines that a collision with an obstacle is unavoidable, that sudden braking has occurred, or that vehicle control is impossible, the system performs seat belt control. During seat belt control, slack in the seat belts is reduced to increase occupant restraint and aid the pretensioner.
6. PRE-COLLISION BRAKE ASSIST CONTROL When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, brake assist is set to standby mode. Then, when the driver depresses the brake pedal, the hydraulic brake pressure is increased to improve braking effectiveness.
7. SUSPENSION CONTROL When it is determined that there is a risk of colliding with an obstacle in front of the vehicle, the AVS is operated to control the damping force, suppress nose diving and rolling, and support collision avoidance through steering.
8. PRE-COLLISION BRAKE CONTROL When the system determines that a collision with an obstacle is unavoidable, the system performs brake control to reduce the vehicle speed. The pre-collision brake response time in cases when there is a vehicle in front has been increased. This results in less damage and injury.
9. PRE-COLLISION SYSTEM CANCEL SWITCH When the pre-collision system cancel switch assembly in the No. 1 instrument panel under cover sub-assembly is turned on, the pre-collision system does not operate. HINT: While the pre-collision system cancel switch is ON, the combination meter's PCS indicator light blinks.
10. PRE-COLLISION SYSTEM OPERATING CONDITION Vehicle Condition Pre-collision Alarm Pre-collision Seat Belt (Sudden braking or vehicle control is not possible) Pre-collision Seat Belt (Avoiding collision is not possible) Pre-collision Brake Assist Pre-collision Brake Suspension Control Power switch off or on (ACC) X X X X X X When warning message is displayed on multi-information display *1 *1 *1 *1 *1 *1 When seat belt(s) are fastened o *2 *2 o o o When own vehicle speed is 15 km/h (10 mph) or more, regardless of relative speed X o X X X X When own vehicle speed is 15 km/h (10 mph) or more and relative speed is 15km/h (10 mph) X X X X o X When own vehicle speed is 5 km/h (4 mph) or more and relative speed is 30 km/h (19 mph) X X o X X o When own vehicle speed is 30 km/h (19 mph) or above, and relative speed of other vehicle is 30 km/h (19 mph) or above X X X o X X When vehicle collides with object outside detection range of front millimeter wave radar sensor (side collision, etc.) X *3 X X X X When front millimeter wave radar sensor cannot detect possible collision object X *3 X X X X When pre-collision system cancel switch ON X X X X X X HINT: o: Operation X: Not operation *1: Inoperative parts are different depending on malfunction areas *2: Only operates when seat belt is fastened *3: Pre-collision seat belts may operate
11. PRECAUTION FOR MILLIMETER WAVE RADAR SENSOR When the millimeter wave radar sensor detects an object in front of the vehicle under the conditions described below, the driving support ECU may determine that a collision is unavoidable, and activates the pre-collision system. However, this is not abnormal. TEXT IN ILLUSTRATION *a There are objects on the side of the road at the beginning of a curve (a guardrail, street lamp, billboard, etc.). *b Passing an oncoming vehicle on a curve. *c There is an oncoming vehicle when making a right turn. *d Crossing a narrow metal bridge. *e There are metal objects on the road. *f Approaching leading vehicle suddenly. *g Electrical Toll Collection gate. (React to bar.) *h Crossing an overpass, traffic sign, signboard *i The vehicle height drastically changes (nose-up, nose-down). *j Misalignment of millimeter wave radar occurs. (re-install, collision, etc) *k There are metal objects at the bottom of a decline (a metal plate covering road construction, a mesh drain cover, a manhole, etc.) *l There is a billboard or sign at the top of an incline. *m Roughness on road surface. - - HINT: The pre-collision system does not activate when the pre-collision sensor detects safety cones and other plastic objects. The pre-collision system may or may not activate when the pre-collision sensor detects the following objects: people, bicycles, motorcycles, trees, animals and snow fences. Object Type Example Object that cannot be detected Plastic items (safety cones) Object that cannot always be detected People, bicycles, motorcycles, trees, animals, snow fences, etc.

FAIL-SAFE CHART [03/2012 - ]

1. FAIL SAFE FUNCTION When a malfunction occurs in part of the pre-collision system, "Check PCS system" or "PCS temporarily not available" is displayed on the multi-information display. Depending on the malfunction, the pre-collision system may stop operating. When the driving support ECU determines that obstacle recognition is not possible due to dirt on the radiator grille, or millimeter wave radar sensor, or due to snow or other adverse conditions, "PCS temporarily not available" is displayed on the multi-information display, and operation of systems not controlled by the seat belt control ECU are stopped. Also, when obstacle recognition becomes possible, the display stops and normal control returns. If the seat belt control ECU overheating prevention function operates, "PCS temporarily not available" is displayed on the multi-information display, and pre-collision seat belt control operation stops. Also, when the temperature drops and pre-collision seat belt control becomes possible, the display stops and normal control returns. If there is a malfunction in the lane recognition camera or driver monitor camera, "Check PCS system" is displayed on the multi-information display, and only the millimeter wave radar sensor is able to determine when there is a collision. However, the control operation does not stop.