TOYOTA SRS SYSTEMS 1986-2002 THEORY OF OPERATION The Supplemental Restraint System (SRS) or airbag, ( pyrotechnic explosive device), works with the seat belts to protect the driver and the front seat passenger by deploying the airbag, ( pyrotechnic explosive device) during certain front and side impact accidents. The SRS consists of a series of sensors, airbag, ( pyrotechnic explosive device) module(s), spiral cable, steering wheel pad, diagnosis system, ignition control, drive circuit, SRS warning lamp, connectors and wires. Sensors are set in line. They work in separate, redundant circuits. Power supply and ground circuits also have built-in redundancy. airbag, (pyrotechnic explosive device) deployment occurs instantaneously when a safing sensor and a front airbag, (pyrotechnic explosive device) sensor and/or airbag, ( pyrotechnic explosive device) sensor simultaneously detect deceleration greater than a specified value. When a deceleration force acts on sensors, electric current is sent through airbag, (pyrotechnic explosive device) clockspring to igniter. This generates gas, rapidly increasing pressure inside bag. The inflated bag breaks open steering wheel pad or instrument panel. Inflation ends as gas discharges through rear and/or side bag holes and the airbag, ( pyrotechnic explosive device) deflates. The SRS also contains a self-diagnostic feature. If an SRS malfunction or fault condition is detected, the instrument panel SRS warning lamp will light.The airbag, ( pyrotechnic explosive device) sensor assembly is mounted on the floor under the console box. This assembly consists of a airbag, ( pyrotechnic explosive device) sensor, safing sensor, diagnosis circuit, ignition control, drive circuit and a backup power source. It receives signals from the airbag, ( pyrotechnic explosive device) sensors and determines whether the SRS must be activated or not. The sensor assembly also contains a diagnosis circuit which will light the instrument panel SRS warning lamp.The front airbag, ( pyrotechnic explosive device) sensors are mounted inside each of the front fenders. These units are the mechanical type and are connected in parallel. When a sensor detects deceleration force above a predetermined value in a collision, the internal fixed and roller points make contact, sending a signal to the airbag, ( pyrotechnic explosive device) sensor assembly. Side airbag, (pyrotechnic explosive device) sensors are mounted in the right-hand and left-hand center pillar. The side airbag, ( pyrotechnic explosive device) sensor assembly consists of a side airbag, ( pyrotechnic explosive device) sensor, safing sensor, diagnosis circuit and ignition control drive circuit. It receives signals from the side airbag, (pyrotechnic explosive device) sensors and judges whether the SRS side airbag, ( pyrotechnic explosive device) must be activated. The SRS airbag, ( pyrotechnic explosive device) warning lamp is located on the instrument panel and alerts the driver if an SRS fault condition is detected by the self-diagnosis circuit. Under normal operating conditions, the lamp will light for approximately six seconds when the ignition is turned to the On position, then go off. If a problem is detected in the SRS system the warning lamp will remain lit. Camry models equipped with natural gas engines and Corolla models have a switch which automatically cuts off the fuel supply in the event of a frontal collision, similar to a FORD inertia switch. Some models are equipped with seat belt pretensioners. These are located on the center pillars and will tighten the seat belts in the event of a frontal collision. The seat belt pretensioner is a component of the front seat outer belt and contains a squib, gas generanting, wire and piston. These systems are used in conjunction with the front driver and passenger airbag, ( pyrotechnic explosive device) system. SRS SYSTEMS 2003-2011 Hybrid Vehicles Stating in 1999 The hybrid system contains a 288 volt high-voltage system with a nickel metal hydride solution of potassium hydroxide. All high-voltage wire harness connectors are orange in color. The high-voltage battery and other components have (High Voltage) caution labels attached. Do not carelessly touchthese wires and components. Serious injury or electrocution could occur if these precautions are ignored. If at anytime during service of the vehicle the skin comes into contact with the battery electrolyte, immediately wash with a saturated boric acid solution or a large amount of water. Remove any clothing that may have come into contact with electrolyte. Prior to performing any repair procedures on hybrid vehicles, deactivate the high-voltage system using the following procedure: 1. Turn ignition switch off. If ignition switch cannot be turned off, remove ignition fuse from HV relay block or disconnect battery ground cable from auxiliary battery. 2. Locate high, voltage battery service plug. 3. Wearing suitable insulated gloves, remove service plug. 4. Wait at least five minutes to allow the condenser inside the inverter to discharge system voltage. 5. When performing service procedures on these vehicles, do not carry metal objects that can be dropped and cause a short circuit. 6. If it is necessary to disconnect a high voltage connector or terminal, immediately insulate connector or terminal with suitable insulation tape. 7. Do not attempt to start engine or place vehicle in a READY ON state with service plug removed as damage to ECU OTHER Non-HYBRID MODELS THEORY OF OPERATION The Supplemental Restraint System (SRS) or airbag, (pyrotechnic explosive device) works together with seat belts to protect the driver and, if equipped, the front seat passenger by deploying airbag, (pyrotechnic explosive device) (s) during certain front and side impact accidents. The SRS consists of a series of sensors, airbag, (pyrotechnic explosive device) module(s), spiral cable, steering wheel pad, diagnosis system, ignition control, drive circuit, SRS warning lamp, connectors and wires. Sensors work in separate circuits. Power supply and ground circuits also have built-in redundancy.airbag, ( pyrotechnic explosive device) deployment occurs instantaneously when a safing sensor and a front airbag, (pyrotechnic explosive device) sensor and/or airbag, (pyrotechnic explosive device) sensor simultaneously detect deceleration greater than a specified value. When a deceleration force acts on sensors, electric current is sent through airbag, (pyrotechnic explosive device) clockspring to igniter. This generates gas, rapidly increasing pressure inside bag. The inflated bag breaks open steering wheel pad or instrument panel. Inflation ends as gas discharges through rear and/or side bag holes and the airbag, (pyrotechnic explosive device) deflates. The SRS also contains a self-diagnostic feature. If an SRS fault or fault condition is detected, the instrument panel SRS warning lamp will light.The airbag, ( pyrotechnic explosive device) sensor assembly is mounted on the floor under the console box. This assembly consists of a crash sensor, safing sensor, diagnosis circuit, ignition control, drive circuit and a backup power source. It receives signals from the airbag, sensors and determines whether the SRS must be activated or not. The sensor assembly also contains a diagnosis circuit which will light the instrument panel SRS warning lamp. The front airbag, sensors are mounted inside each of the front fenders. These units are the mechanical type and are connected in parallel. When a sensor detects deceleration force above a predetermined value in a collision, the internal fixed and roller points make contact, sending a signal to the airbag, ( pyrotechnic explosive device) sensor assembly. Side airbag, (pyrotechnic explosive device) sensors are mounted in the right-hand and left-hand center pillar. The side airbag, (pyrotechnic explosive device) sensor assembly consists of a side airbag, (pyrotechnic explosive device) sensor, sating sensor, diagnosis circuit and ignition control drive circuit. It receives signals from the side airbag, (pyrotechnic explosive device) sensors and judges whether the SRS side airbag, ( pyrotechnic explosive device) must be activated. The SRS airbag, ( pyrotechnic explosive device) warning lamp is located on the instrument panel and alerts the driver if an SRS fault condition is detected by the self-diagnosis circuit. Under normal operating conditions, the lamp will light for approximately six seconds when the ignition is turned to the On position, then go off. If a problem is detected in the SRS system the warning lamp will remain lit. Camry models equipped with natural gas engines and Corolla models have a switch which automatically cuts off the fuel supply in the event of a frontal collision. Some models are equipped with seat belt pretensioners. These are located on the center pillars and will tighten the seat belts in the event of a frontal collision. The seat belt pretensioner is a component of the front seat outer belt and contains a squib, gas generanting, wire and piston. These systems are used in conjunction with the front driver and passenger airbag, (pyrotechnic explosive device) system. NOTE: DO NOT USE A MULTIMETER TO MEASURE RESISTANCE OR CONTINUITY ACROSS THE AIRBAG PYROTECHNIC DEVICE. THE END RESULT MAY BE A BLOWN AIRBAG ------------------------------------------------------------------------------ LEXUS 1990-2011 THEORY OF OPERATION The Supplemental Restraint System (SRS) or pyrotechnic device works together with the seat belts to protect driver and passenger by deploying airbags during certain frontal collisions. Front seat belt pretensioners are also used. In a front end collision, the airbag crash sensors will detect if the shock is greater than the specified value. If the shock is greater than the specified value, the airbag will inflate instantaneously to help reduce injury to the occupants. The SRS also contains a self diagnostic feature. If a malfunction is detected in the SRS, a warning lamp on the instrument panel will be illuminated. The airbag front sensors are mounted inside each of the front fenders. The sensor units are the mechanical type and are connected in parallel. When the sensor detects deceleration force above a pre-programmed value in a collision, the fixed and roller points in the sensor make contact, sending a signal to the center airbag sensor assembly. The center air bag sensor assembly is mounted on the floor under the console box. The center airbag sensor assembly consists of a center airbag sensor, safing sensor, diagnosis circuit, ignition control, drive circuit and a back up power source. It receives signals from the airbag crash sensors and determines whether the SRS must be activated or not. The center airbag sensor assembly also contains a diagnosis circuit which will illuminate a warning lamp on the instrument panel. The airbag warning lamp is located on the instrument panel. It is used to alert the driver when a malfunction in the SRS is detected by the center airbag sensor assembly self-diagnosis circuit. In normal operating condition when the ignition switch is turned to the ACC or On position, the lamp will illuminate for about six seconds and then turn off.The driver side airbag and explosive detonator of the SRS are stored in the steering wheel. ------------------------------------------------------------------------------ SCION THEORY OF OPERATION The Supplemental Restraint System (SRS) or pyrotechnic device works together with seat belts to protect the driver and, if equipped, the front seat passenger by deploying airbag(s) during certain frontal collisions. The SRS consists of a series of sensors, airbag module(s), clockspring, steering wheel pad, diagnosis system, ignition control, drive circuit, SRS warning lamp, connectors and wires.