The air bag system last used on the 1990 Ninety Eight is referred to as the Inflatable Restraint (ir) system. The air bag is designed to deploy when the vehicle is involved in a front end collision of sufficient force, up to 30 degrees off center line of the vehicle. The steering column still continues to be collapsible, the same as vehicle without an air bag.
This system has an energy reserve, which can store a large enough electrical charge to deploy the air bag for a period of 15 seconds after the battery has been disconnected or damaged. This system must be disabled if any service is to be performed on the ir system or steering wheel assembly.
The system consists of a control module known as the Passenger Compartment Sensor/Diagnostic Module (pcsdm), a power supply module, Energy Reserve Module (erm), steering wheel or inflator module, a coil assembly that assures electrical continuity to the inflator module as the steering wheel is turned, forward sensor, arming sensor, and an indicator lamp. Diagnostics are carried out by the pcsdm.
Passenger Compartment Sensor/Diagnostic Module
The pcsdm contains the passenger compartment sensor and the diagnostic module. The diagnostic module processes the vehicle deceleration and forward sensor signal to determine if deployment is necessary. A deployment signal is sent to the inflator module when the forward sensor or when passenger compartment sensor closes and the arming sensor closes at the same time. This module also controls the indicator lamp.
This system can store codes, but they must be read with tester J-36884, or equivalent. This system utilizes the indicator lamp to warn of a problem, but flash code diagnostics are not possible.Arming and Forward Sensors
All sensors are specifically calibrated to each series vehicle and keyed to the mounting brackets. Great care must be taken to mount the correct sensors on the vehicle being serviced. The sensors, mounting brackets and wiring harness must never be modified from original design.
The forward sensor is a normally open switch. In an accident, the sensor closes and the electrical circuit is complete. If the forward sensor and the arming sensor close at the same time the air bag will deploy.
The arming sensor is a normally open switch that closes during deceleration encountered in an accident. The arming sensor is wired in series with the steering module. A resistor is connected in parallel with the switch and allows a small amount of current to flow through the circuit for diagnostic purposes.Power Supply Module
The power supply module provides a boosted voltage to the ir system to ensure deployment during low voltage conditions, perform limited internal diagnostics and monitor the integrity of the ir wiring and 8-terminal connector.Energy Reserve Module
The reserve module provides sufficient electrical power to deploy the air bag even if the vehicle battery is damaged or disconnected.Inflator Module
The inflator module, consists of the air bag, electrical initiator and inflator assembly. If an accident occurs, the inflatable bag is deployed by a gas producing generator. The trim cover opens at the seam as the bag is deployed.Indicator Lamp
The red inflatable restraint lamp will light for 5-15 seconds when the ignition is turned no . This informs the driver that the system is functioning properly. If the lamp does not operate correctly, this indicates an ir system fault and the system should be checked.Fuse Panel
Some vehicles with have a specific fuse panel located in the lower instrument panel trim pad. It is hinged to swing out for easy access. On other models the ir fuse is located with the other fuses.Knee Bolster
The knee bolster is used to absorb energy and control the driver's forward movement during an accident by limiting leg movement.Wiring Harness and Connectors
The wiring harness and connectors for the ir system are of special design. Any wiring repairs should be done using tool kit J-38125, or equivalent. Always use the crimp and seal splice sleeves contained in this wiring repair kit. If damage is done to a component pigtail the component must be replaced.
The Initiator circuit has a special yellow shorting bar connectors that help prevent accidental deployment during service. The ir wire harness components are part of the body wiring harness assembly. Sections of harness which include more than a 1 ir wire are wrapped in yellow tape.
DISARMING THE SYSTEM
Proper and safe operation requires the sensor, brackets and wiring to be installed in the exact locations of design. All components service must be exactly aligned and tighten to exact torque specification. It is not advisable to service the air bag system. The information provided is to help you understand the system and disarm the system if other non-air bag system service are to be performed.
- Read all service precautions.
- Turn the steering wheel so wheels are facing straight ahead and turn the ignition switch to lock .
- Disconnect the negative battery cable and tape the end of cable to avoid possible terminal contact.
- Remove the ir fuse.
ARMING THE SYSTEM
- Read all service precautions.
- Disconnect the negative battery cable and tape the end of cable to avoid possible terminal contact. Remove the ir fuse.
- Reconnect the ir inflator connector at the base of the steering column, if disconnected.
- Install the sound insulator and lamp, if removed.
- Install the ir fuse and connect the battery cable.
- Turn the ignition switch to the run position and observe the supplemental inflatable restraint lamp on the instrument cluster. The lamp should remain lit for 5-15 seconds, and then go out. If the lamp does anything else, have the system checked.
AIR BAG SYSTEM INSPECTION FOLLOWING DEPLOYMENT
Proper operation of the sensors and ir system requires that any repairs to the vehicle structure return it to its original production configuration. Deployment requires replacement of the inflator module, arming sensor and pcsdm. Any visible damage to the sensors and/or their respective mounting brackets requires replacement, whether a deployment has occurred or not.
All components, including harnesses and brackets, must be inspected. Any wiring damage must only be repaired using repair kit J-38125-A. If the air bag was deployed, inspect the coil assembly for scorching or melting damage and replace if necessary. Never attempt to repair any ir system parts. Service is by replacement only. Never interchange parts from another vehicle.
The steering column jacket assembly should be visually checked for damage and collapsing or felt for looseness when pushed or pulled by hand. The steering shaft should be checked for shearing of the injected plastic, requiring the replacement of the steering shaft. The steering shaft runout must be checked if the collision caused frame damage that could have bent the steering shaft.