Toyota Tercel 1984-1994 Repair Guide

General Information

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SYSTEM OPERATION



See Figure 1

The Supplemental Restraint System (SRS), together with the seat belt, is designed to help protect the driver during frontal impact.

When the vehicle is involved in a frontal collision within the activation area and the shock is greater than a predetermined level, the SRS is automatically activated. A safing sensor is designed to close at a deceleration rate less then the front and center air bag sensors. Air bag activation occurs when the safing sensor and either a front air bag sensor and/or the center air bag sensor contacts close simultaneously.



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Fig. Fig. 1: Air bag deployment activation area

SYSTEM COMPONENTS



Air bag

See Figures 2 and 3

The air bag of the SRS is stored in the steering wheel pad and cannot be disassembled. A gas generant inflates the air bag during a frontal collision of sufficient force. The bag deflates as the gas is discharged through the vent holes at the bag's rear or side.



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Fig. Fig. 2: Air bag component locations



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Fig. Fig. 3: The air bag is stored in the steering wheel pad

Spiral Cable

See Figure 4

A spiral cable is used as an electrical joint from the air bag controls to the steering wheel.



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Fig. Fig. 4: The spiral cable electrically links the air bag controls to the air bag

SRS Warning Light

See Figure 5

The SRS warning light is located in the combination meter. It goes on to alert the driver when a malfunction is detected by the center air bag sensor assembly during system self-diagnosis. Under normal operating conditions, the light goes ON for about 6 seconds, then goes OFF when the ignition key is turned to the ACC or ON position.



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Fig. Fig. 5: SRS warning light locations

Front Air bag Sensors

See Figure 6

A front air bag sensor is mounted inside each of the front fenders. The sensor unit is basically a mechanical switch. When the sensor detects a deceleration force above a predetermined level in a collision, the contacts in the sensor close, sending a signal to the center air bag sensor assembly. The sensor cannot be disassembled.



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Fig. Fig. 6: A common front air bag sensor

Center Air bag Sensor Assembly

See Figure 7

The center air bag sensor assembly is mounted on the floor inside the console. The center air bag sensor assembly consists of a center air bag sensor, safing sensors, air bag ignition control and a self-diagnosis circuit. It receives signals from the air bag sensors and determines whether or not the SRS must be activated.



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Fig. Fig. 7: The center air bag sensor assembly consists of several control circuits

SRS Connectors

All connectors in the SRS are colored yellow to distinguish them from other connectors and are specifically designed for use in the SRS.

SYSTEM PRECAUTIONS



The following service precautions should always be followed:



Always disarm the system before performing any work on the vehicle
 
Do not disassemble any air bag system components
 
SRS service and diagnosis should only be performed by a certified technician
 
The SRS must be inspected 10 years after the vehicle's date of manufacture
 
Always have the SRS inspected when the vehicle has been involved in a collision (even in cases of minor collisions) where the air bag did not deploy
 
Any visible damage to SRS components requires replacement
 
Never strike or jar a sensor, air bag deployment could occur
 
Never subject the vehicle to temperatures higher than 200°F (93°C), such as in a paint booth, without first disabling the system and having the SRS components removed by a certified technician
 
Always touch a vehicle ground after sliding across the seat or walking across vinyl/carpeted floors to avoid static discharge damage to the SRS
 

DISARMING THE SYSTEM



  1. Turn the ignition switch to the LOCK position.
  2.  
  3. Disconnect the negative battery cable, then insulate it by wrapping it with electrical tape.
  4.  
  5. Wait at least 90 seconds from the time the ignition switch is turned to the LOCK position and the battery is disconnected before performing any further work. The SRS is equipped with a back-up power source. If work is started before 90 seconds have elapsed, air bag deployment may occur.
  6.  

ARMING THE SYSTEM



  1. Connect the negative battery cable.
  2.  
  3. Perform a SRS check by turning the ignition key to the ON or ACC position, but do not start the engine.
  4.  
  5. The warning lamp should illuminate for about 6 seconds. If no malfunctions are detected, the lamp should turn OFF. If it stays ON, have the vehicle serviced immediately by a certified technician.
  6.  

 
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