Toyota Pick-ups/Land Cruiser/4Runner 1989-1996

General Information

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SYSTEM OPERATION




CAUTION
The 1994-96 Toyota trucks are equipped with a Supplemental Restraint System (SRS), which is comprises of a driver's and passenger's (on some models) air bag. Failure to carry out the service operations in the correct sequence could cause the SRS to unexpectedly deploy during servicing the SRS may fail to operate when needed. Before servicing, be sure to read the following items carefully. When a vehicle is involved in a frontal collision in the hatched area and the shock is larger than a predetermined level, the SRS is activated automatically. A safing sensor is designed to tip at a smaller deceleration rate than the air bag sensor. The ignition is caused when a current flows to the squib, which occurs when a safing sensor and the air bag sensor trip simultaneously. When a deceleration force acts on the sensors, two sqibs in the driver's air bag and passenger's air bag (if applicable) ignite and generate gas. The gas that discharges into the driver's and passenger's air bags rapidly increases the pressure inside the bags, breaking open the steering wheel pad and (if applicable) instrument panel.

Bag inflation then ends, and the bags deflate as the gas is discharged through the holes at the bag's rear or side.

SYSTEM COMPONENTS



Steering Wheel Air Bag

See Figure 1

The inflator and bag of the SRS are stored in the steering wheel pad and cannot be disassembled. The inflator contains a igniter charge, sqib, and gas generate. This inflates the bag when instructed by the center air bag sensor.



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Fig. Fig. 1: The air bag is located in the center of the steering wheel

Front Passenger Air Bag

See Figure 2

The inflator and bag of the SRS are stored in the instrument panel and cannot be disassembled. The inflator contains a igniter charge, sqib, and gas generate. This inflates the bag when instructed by the center air bag sensor.



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Fig. Fig. 2: The passenger's air bag is integrated into the instrument panel

Spiral Cable

See Figure 3

The spiral cable is located in the combination switch. This cable is used as an electrical joint from the vehicle body side to the steering wheel.



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Fig. Fig. 3: The spiral cable is wrapped in the combination switch

SRS Warning Light

See Figure 4

The SRS warning light is located on the combination meter. It turns to alert the driver of trouble in the system when a malfunction is detected in the air bag sensor assembly. In normal operating conditions when the ignition switch is turned to the ON or ACC position, the light turns on for about 6 seconds and then turns off.



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Fig. Fig. 4: The SRS warning lamp should light for about six seconds with the key on

Air Bag Sensor Assembly

See Figure 5

The air bag sensor assembly is mounted on the floor inside the console box on Land Cruisers, on the air bag sensor cover on Tacoma and inside each fender on the T100. The air bag sensor assembly consists of an air bag sensor, safing sensor, diagnosis circuit and ignition control. It receives signals from the air bag sensors and judges whether the SRS must be activated or not.



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Fig. Fig. 5: On Land Cruisers, the air bag sensor is mounted on the floor in the center console

SRS Connectors

All connectors in the SRS are colored yellow to distinguish them from the other connectors. These connectors have special functions are specifically designed for the SRS. These connectors use durable gold-platted terminals.

SYSTEM PRECAUTIONS



  1. Work must be started after 90 seconds from the time the ignition switch is turned to the LOCK position and the negative battery cable has been disconnected. The SRS is equipped with a back-up power source so that if work is started within 90 seconds of disconnecting the negative battery cable, the SRS may deploy. When the negative terminal cable is disconnected from the battery, memory of the clock and radio will be canceled. Before you start working, make a note of the contents memorized by the audio memory system. When you have finished working, reset the audio systems and adjust the clock. Never use a back-up power supply from outside the vehicle.
  2.  
  3. In the event that of a minor frontal collision where the air bag does not deploy, the steering wheel pad, front air bag sensors and center air bag sensor assembly should be inspected.
  4.  
  5. Before repairs, remove the air bag sensors if shocks are likely to be applied to the sensors during repairs.
  6.  
  7. Never disassemble and repair the steering wheel pad, front air bag sensors or center air bag sensors.
  8.  
  9. Do not expose the steering wheel pad, front air bag sensors or center air bag sensor assembly directly to flames or hot air.
  10.  
  11. If the steering wheel pad, front air bag sensors or center air bag sensor assembly have been dropped, or there are cracks, dents or other defects in the case, bracket or connectors, have them replaced with new ones.
  12.  
  13. Information labels are attached to the periphery of the SRS components. Follow the instructions of the notices.
  14.  
  15. After arming the system, check for proper operation of the SRS warning light.
  16.  
  17. If the wiring harness in the SRS system is damaged, have the entire harness assembly replaced.
  18.  

DISARMING THE SYSTEM



Work must be started only after 90 seconds from the time the ignition switch is turned to the LOCK position and the negative battery cable has been disconnected. The SRS is equipped with a back-up power source so that if work is started within 90 seconds of disconnecting the negative battery cable, the SRS may deploy. When the negative terminal cable is disconnected from the battery, memory of the clock and radio will be canceled. Before you start working, make a note of the contents memorized by the audio memory system. When you have finished work, reset the audio systems as before and adjust the clock. To avoid erasing the memory of each system, never use a back-up power supply from outside the vehicle.

ARMING THE SYSTEM

Once the negative battery cable is reconnected, the system is armed. Turn the ignition ON . Check that the SRS lamp turns off after about 6 seconds.

 
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