TOYOTA PREVIA 91-97 REPAIR MANUAL

CHASSIS ELECTRICAL 6-9

BATTERY CABLES

Disconnecting The Cables

When working on any electrical component on the vehicle, it is always a
good idea to disconnect the negative (-) battery cable. This will prevent
potential damage to many sensitive electrical components such as the
Engine Control Module (ECM), radio, alternator, etc.

"»Any time you disengage the battery cables, it is recommended
that you disconnect the negative (-) battery cable first. This will pre-
vent your accidentally grounding the positive (+) terminal to the
body of the vehicle when disconnecting it, thereby preventing dam-
age to the above mentioned components.

AIR BAG (SUPPLEMENTAL RESTRAINT SYSTEM)

General Information

I See Figure 14

The air bag system used on Previa vans is referred to as the Supplemen-

tal Restraint System (SRS). The SRS provides additional protection for the

driver (and front passenger on later models) if a forward collision of suffi-

cient force is encountered. The SRS assists the normal seatbelt restraining

system by deploying an air bag, via the steering column.

The center air bag sensor is the heart of the SRS. It consists of safing

sensors, ignition control and drive circuit, 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 connec-

tion check mechanism which detects when the connector to the center air

bag sensor assembly is not properly connected.

Before you disconnect the cable(s), first turn the ignition to the OFF

position. This will prevent a draw on the battery which could cause arcing

(electricity trying to ground itself to the body of a vehicle, just like a spark

plug jumping the gap) and, of course, damaging some components such as

the alternator diodes.

When the battery cable(s) are reconnected (negative cable last), be sure

to check that your lights, windshield wipers and other electrically operated

safety components are all working correctly. If your vehicle contains an

Electronically Tuned Radio (ETR), don't forget to also reset your radio sta-

tions. Ditto for the clock.

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; there-by, preventing the terminals from coming apart.

SYSTEM OPERATION

When the ignition switch is turn to the ON or ACC position, the air bag

warning lamp will turned on for approximately 6 seconds. If no malfunc-

tions are detected in the system, after the 6 second period have elapse, the

warning light will go OFF.

The safing sensors are designed to trip 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 trip 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.

SRS Warning Light

Front Passenger Airbag

Assembly

Front Airbag Sensor LH

Front Airbag Sensor

RH

Center Airbag Sensor Assembly

Steering Wheel Pad

(with Airbag)

Fig. 14 Supplemental Restraint System (SRS) component locations