Toyota Celica 1986-1993 Repair Guide

General Information

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The air bag system used on the Celica is referred to as the Supplemental Restraint System (SRS). The SRS provides additional protection for the driver, if a forward collision of sufficient force is encountered. The SRS assists the normal seat belt restraining system by deploying an air bag.

The center air bag sensor is the heart of the SRS. It consists of safing sensors, inflator ignition control, diagnosis circuit, etc. The center air bag receives signals from the air bag sensors and determines whether the air bag must be activated or not. The center air bag sensor is also used to diagnose system malfunctions.

The air bag warning light circuit is equipped with an electrical connection check mechanism that detects when the connector to the center air bag sensor assembly is not properly connected.

All connectors in the air bag system are colored yellow. These connectors use gold-plated terminals with twin-lock mechanism. This design assures positive locking.

SYSTEM OPERATION



When the ignition switch is turned to the on or ACC positions, the air bag warning lamp will turn on for approximately 6 seconds. If no malfunctions are detected in the system after the 6 second period has elapsed, the warning light will go off.

The safing sensors are designed to go on at a lower deceleration rate than the front or center air bag sensor. When the vehicle is involved in a frontal collision, the shock is great enough to overcome the predetermine level of the front or center air bag sensor. When a safing sensor and a front air bag sensor and/or the center air bag sensor go on simultaneously, it causes the squib of the air bag to ignite and the air bag is deployed automatically. The inflated bag breaks open the steering wheel pad.

The connector of the air bag contains a short spring plate, which provides an activation prevention mechanism. When the connector is disconnected, the short spring plate automatically connects the power source and grounding terminals of the inflator module (squib) to prevent static electricity from deploying the air bag.

SYSTEM COMPONENTS



Front Air Bag Sensor

The front sensors, located inside each front fender, detect deceleration force above a predetermined limit. They must be securely fastened to their mounts at all times.



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Fig. Fig. 1 Air bag system component locationsCelica

Center Air Bag Sensor

The center air bag sensor is mounted on the floor inside the rear of the center cluster. The center sensor determines whether or not the air bag should be deployed and is also used to diagnose system malfunctions.

Spiral Cable

The spiral cable, part of the combination switch, ensures uninterrupted electrical contact to the air bag while allowing rotation of the steering wheel. The spiral cable is also referred to as a clock spring.

Air Bag

The air bag, located in the steering wheel pad, deploys in the event of a frontal collision of sufficient force. Special precautions must be taken when performing service on a vehicle equipped with an air bag.

Warning Lamp

The air bag warning lamp, located on the combination meter, is used to alert the driver of a malfunction within the air bag system.

SERVICE PRECAUTIONS




CAUTION
To avoid deployment when servicing the sir system or components in the immediate area, do NOT use electrical test equipment such as battery or A.C. powered voltmeter, ohmmeter, etc. or any type of tester other than specified. Do NOT use a non-powered probe tester. To avoid personal injury, all precautions must be strictly adhered to.



Wait at least 90 seconds from the time that the ignition switch is turned to the lock position and the battery is disconnected before performing any further work.
 
Do NOT disassemble any air bag system components.
 
ALWAYS carry an inflator module with the trim cover pointed away.
 
ALWAYS place an inflator module on the workbench with the pad side facing upward, away from loose objects.
 
After deployment, the air bag surface may contain sodium hydroxide dust. ALWAYS wear gloves and safety glasses when handling the assembly. Wash hands with mild soap and water afterwards.
 
When servicing any SRS parts, discard the old bolts and replace with new ones, torquing them to specifications.
 
The SRS must be inspected 10 years after the vehicle's manufacture date shown on the certification label located on the left front door latch post.
 
ALWAYS inspect the air bag sensors and steering wheel pad, when the vehicle has been involved in a collision (even in cases of minor collision) where the air bag did not deploy.
 
ALWAYS use a fine needle test lead for testing, to prevent damaging the connector terminals.
 
NEVER measure the resistance of the air bag. This may cause the air bag to deploy due to the current of the ohmmeter.
 
NEVER disconnect any electrical connection with the ignition switch on unless instructed to do so in a test.
 
Before disconnecting the negative battery cable, make a record of the contents memorized by each memory system like the clock, audio, etc. When service or repairs are completed make certain to reset these memory systems.
 
Avoid touching component connector pins.
 
Leave new components and modules in the shipping package until ready to install them.
 
ALWAYS touch a vehicle ground after sliding across a vehicle seat or walking across vinyl or carpeted floors to avoid static charge damage.
 
All sensors are specifically calibrated to a particular vehicle. Do NOT interchange sensors between models or years.
 
The sensors, mounting brackets and wiring harness must NEVER be modified from original design or repaired.
 
NEVER strike or jar a sensor, or deployment could happen.
 
The inflator module must be deployed before it is scrapped.
 
Any visible damage to sensors requires component replacement.
 
NEVER bake paint on vehicle, such as in a paint booth, or subject the vehicle to temperatures exceeding 200°F (93°C), without disabling the air bag system and removing the inflator module, crash zone sensors, SRS diagnosis unit and the spiral cable.
 
NEVER allow welding cables to lay on, near or across any vehicle electrical wiring.
 
Caution labels are important when servicing the air bag system in the field. If they are dirty or damaged, replace them with new ones.
 

DISARMING THE SYSTEM



Procedure
  1. Turn the ignition switch to the Lock position.
  2.  
  3. Disconnect the negative battery terminal and isolate it by wrapping it with electrical tape.
  4.  
  5. Wait at least 90 seconds from the time that the ignition switch is turned to the lock position and the battery is disconnected before performing any further work.
  6.  

ENABLING THE SYSTEM



Procedure
  1. Reconnect the negative battery cable.
  2.  
  3. Perform the air bag warning light check by turning the ignition key to the On or Acc positions, but do NOT start the engine. The air bag warning lamp will illuminate for approximately 6 seconds. If no malfunctions are detected in the system, the warning light will go off. If it stays on, bring the vehicle to a qualified technician, otherwise the air bag may not deploy in a collision, causing personal injury or death.
  4.  

 
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