Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
AIR BAG AND SAFETY BELT PRETENSIONER SUPPLEMENTAL RESTRAINT SYSTEM (SRS)The air bag supplemental restraint system (SRS) is designed to provide increased collision protection for front seat and second row outboard occupants in addition to that provided by the three-point safety belt system. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantage of the SRS.
There are two supplemental restraint systems used for the 2002 Explorer/Mountaineer. The following is a breakdown of the two systems.
Vehicles built up to 03/2002 contain single stage deployment driver and front passenger air bag modules. These vehicles can also be equipped with optional side air curtains that deploy from the A-pillar to the C-pillar upon a side impact.
Vehicles built 03/2002 onward contain dual stage deployment (advanced restraint system) driver and front passenger air bag modules. These vehicles can also be equipped with optional safety canopies that deploy from the A-pillar to the C-pillar upon a side impact or if a rollover condition is detected. A unique restraints control module (RCM) is used on these vehicles which will detect a potential rollover condition. In addition, a front impact severity sensor is mounted to the lower radiator support, a seat position sensor is mounted to the driver seat and a usage detection switch is added to the front driver and passenger outboard buckles.
Identifying the two similar systems can be done in one of several ways:
- Checking the restraints control module (RCM) part number through the use of a scan tool will identify the vehicle as built up to 03/2002 or built 03/2002 onward. If the vehicle was "built up to 03/2002" the first number in the RCM part number will be the number one, indicating a 2001 part number. If the vehicle was "built 03/2002 onward" the first number in the RCM part number will be the number two, indicating a 2002 part number.
- Looking through the opening under the grill, a vehicle built 03/2002 onward will have a front impact severity sensor attached to the lower radiator support. A vehicle built up to 03/2002 will not have this sensor. It may be necessary to look up and under the deflector shield to see this sensor.
Passenger Air Bag Module Electrical Connector, Vehicles Built Up To 03/2002
Passenger Air Bag Module Electrical Connector, Vehicles Built 03/2002 Onward
- With the glove compartment open past its stops and looking up into the opening, a vehicle built up to 03/2002 will have a two wire connector for the passenger air bag module and accept restraint system diagnostic tool 418-F088 (105-R0012). A vehicle built 03/2002 onward will have a larger four wire connector for the passenger air bag module and accept restraint system diagnostic tool 418-133 (014-R1076).
Safety Belt Buckle and Pretensioner Electrical Connector, Vehicles Built Up To 03/2002
Safety Belt Buckle and Pretensioner Electrical Connector, Vehicles Built 03/2002 Onward
- Vehicles built up to 03/2002 will have safety belt buckle pretensioner electrical connectors under the front seats that will not accept a restraint system diagnostic tool. Vehicles built 03/2002 onward will have safety belt buckle pretensioner electrical connectors under the front seats that will accept restraint system diagnostic tool 418-133 (014-R1076).
See the following illustrations for component location of vehicles built up to 03/2002 or vehicles built 03/2002 onward.
Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - Vehicles Built Up To 03/2002 (Part 1):
Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - Vehicles Built Up To 03/2002 (Part 2):
Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Deplayable Components - Vehicles Built 03/2002 Onward:
Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Sensor Components - Vehicles Built 03/2002 Onward:
Side Air Curtain and Safety Canopy
NOTE: When a side air curtain module needs to be installed and the replacement part is a safety canopy, safety canopies must be installed in place of both side air curtain modules; also, new C-pillar trim panels designed for use with safety canopies must be installed in place of the C-pillar trim panels designed for use with the side air curtains. A vehicle must not have a side air curtain and a safety canopy present on the same vehicle.
Vehicles built up to 03/2002 can be equipped with optional side air curtains for protection during side impacts. Vehicles built 03/2002 onward can be equipped with optional safety canopies for protection during side impacts or rollovers. A safety canopy can be installed in place of a side air curtain but a side air curtain must never be installed in place of a safety canopy.
Vehicles equipped with side air curtains or safety canopies require a specific headliner and C-pillar trim panels. When installing a new headliner on a vehicle equipped with side air curtains or safety canopies, make sure a headliner and C-pillar trim panels for side air curtains or safety canopies are being used. The word "AIRBAG" will appear on the headliner where it meets each B and C-pillar trim panel.
The side air curtain module or safety canopy:
- is installed as an assembly.
- is mounted above the headliner.
- attaches from the A-pillar frame to the C-pillar frame.
C-Pillar Trim Panel
C-Pillar Trim Panel For Safety Canopy:
Vehicles equipped with safety canopies require specific C-pillar trim panels. These C-pillar trim panels were introduced on vehicles built 03/2002 onward for use specifically with safety canopies and must be used on vehicles built up to 03/2002 when safety canopies are being installed in place of side air curtains. There is only one style of C-pillar trim panel to be installed on a vehicle with safety canopies. If not, the safety canopy may not deploy correctly.
Side Air Curtains
Side Air Curtain, Vehicles Built Up To 03/2002:
The parts stock of the side air curtain module for vehicles built up to 03/2002 will be depleted. When this parts stock is depleted, a safety canopy will then have to be installed on vehicles built up to 03/2002. Self-tapping screws will be used to tap the C-pillar weld nuts to fasten the C-pillar tether cord slide mechanism. If a vehicle built up to 03/2002 is to receive a safety canopy, it will be necessary that a C-pillar trim panel designed for use on a safety canopy must be installed onto a vehicle built up to 03/2002.
Safety Canopies
Safety Canopy, Vehicles Built 03/2002 Onward:
A safety canopy will have a C-pillar tether cord slide mechanism as shown in the illustration above (vehicles built 03/2002 onward). A side air curtain will not have a C-pillar tether cord slide mechanism (vehicles built up to 03/2002). A side air curtain module must never be installed in place of a safety canopy module.
If a vehicle built up to 03/2002 is to receive a safety canopy, it will be necessary that a C-pillar trim panel designed for use with a safety canopy must be installed onto a vehicle built up to 03/2002. There is only one style of C-pillar trim panel to be installed on a vehicle with safety canopies. If not, the safety canopy may not deploy correctly.
Side Air Curtain or Safety Canopy Bridge Resistor
CAUTION: Do not deactivate the side air curtain module or safety canopy module circuit by removing the bridge resistor from the electrical connector.
If the side air curtain or safety canopy bridge resistor is removed, an open circuit fault will be generated by the restraints control module (RCM).
If a restraint system diagnostic tool is installed at the side air curtain or safety canopy electrical connector, a low resistance fault will be generated.
The side air curtain or safety canopy bridge resistor:
- is equipped on vehicles without side air curtain or safety canopy modules.
- must not be removed during deactivation.
- is located at the LH C-pillar.
Driver Air Bag Module
The driver air bag module:
- is installed new as an assembly.
- is mounted in the center of the steering wheel.
- is not interchangeable between vehicles built up to 03/2002 and vehicles built 03/2002 onward.
Clockspring
The clockspring:
- is mounted on the steering column, behind the steering wheel.
- continuously transfers electrical signals from the driver air bag module to the restraints control module (RCM).
- is not interchangeable between vehicles built up to 03/2002 and vehicles built 03/2002 onward.
Passenger Air Bag Module
The passenger air bag module:
- is installed new as an assembly.
- is mounted in the passenger side of the instrument panel.
- is not interchangeable between vehicles built up to 03/2002 and vehicles built 03/2002 onward.
Safety Belt Pretensioners
As part of the SRS the safety belt buckles are equipped with pretensioners. The safety belt buckle pretensioners remove excess slack from the safety belt webbing. The pretensioners are activated by the restraints control module (RCM) when the module detects a crash event force exceeding a programmed limit. The safety belt buckle pretensioners are not interchangeable from vehicles built up to 03/2002 to vehicles built 03/2002 onward.
Safety Belt Buckle Switches
Vehicles built up to 03/2002 will have a driver safety belt buckle equipped with a switch which communicates with the generic electronic module (GEM).
Vehicles built 03/2002 onward will have both driver and front outboard passenger safety belt buckles equipped with a switch. The safety belt buckle switch indicates to the restraints control module (RCM) whether the driver and front outboard passenger safety belt buckles are connected or disconnected.
Seat Track Position Sensor - Vehicles Built 03/2002 onward
The seat track position sensor is a hall-effect sensor located on the driver seat track. The seat track position sensor informs the restraints control module (RCM) of the driver seat position. Based on programmed limits, the seat track position sensor will inform the RCM of the driver seat position. The RCM uses this information in determining the deployment rate of the dual-stage driver air bag module.
Restraints Control Module (RCM)
WARNING:
- Do not handle, move or change the original horizontal mounting position of the restraints control module (RCM) while the RCM is connected and the ignition switch is ON. Failure to follow these instructions may result in the inadvertent deployment of the safety canopy modules and risk of personal injury.
- The restraints control module (RCM) orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) has been involved in a collision in which the center tunnel area has been damaged, inspect the mounting and bracket for deformation. If damaged, the RCM must be replaced whether or not the air bags have deployed. In addition, make sure the area of the RCM mounting is restored to its original condition.
NOTE: When installing a new restraints control module (RCM), always make sure the correct RCM is being installed. If an incorrect RCM is installed, erroneous DTCs will result.
The restraints control module is not interchangeable between vehicles built up to 03/2002 and vehicles built 03/2002 onward.
The restraints control module carries out the following functions:
- deploys the air bag(s) in the event of a deployable crash.
- activates the safety belt buckle pretensioners to remove slack from the safety belt.
- monitors the SRS for faults.
- illuminates the air bag indicator if a fault is detected.
- flashes the air bag indicator to indicate the lamp fault code (LFC) detected.
- communicates through the data link connector (DLC) the current or historical Diagnostic Trouble Codes (DTCs).
- signals the generic electronic module (GEM) (vehicles built up to 03/2002) or the instrument cluster module (vehicles built 03/2002 onward) to activate a chime if the air bag indicator is not available and another SRS fault exists.
The RCM monitors the SRS for possible faults. If a fault is detected while the ignition switch is in the ON position, the RCM will illuminate the air bag indicator located in the instrument cluster.
When the ignition is cycled (turned off and then on), the air bag indicator will prove out by lighting for six seconds and then off for two seconds. After the prove out, the air bag indicator will then flash the two-digit LFC. If a SRS fault exists, the air bag indicator will flash the LFC five times, then it will remain illuminated for the rest of the key cycle. The RCM will also communicate the current and historical DTCs through the DLC, to the scan tool. If the air bag indicator does not function, and the system detects a fault condition, the RCM will signal the GEM or the instrument cluster module to activate an audible chime. The chime is a series of five sets of five tone bursts. If the chime is heard, the SRS and the air bag indicator require repair.
LFCs are prioritized. If two or more faults occur at the same time, the fault having the highest priority will be displayed. After that fault has been corrected, the next highest priority fault will be displayed.
The RCM includes a backup power supply. This feature provides sufficient backup power to deploy the air bags in the event that the ignition circuit is lost or damaged during impact. The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.
Electrical System
The electrical system that supports the air bag SRS:
- is powered from the battery through the ignition circuit.
- provides the electrical path from the restraints control module (RCM) to the SRS components.
- provides the electrical path from the RCM to the air bag indicator.
- provides the electrical path from the RCM to the data link connector (DLC).
- provides the electrical path from the RCM to the generic electronic module (GEM) or instrument cluster module.
Sensors
WARNING: Vehicle sensor orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) is involved in a collision, inspect the sensor mounting bracket and wiring pigtail for deformation. Replace and correctly position the sensor or any other damaged supplemental restraint system (SRS) components whether or not the air bag is deployed.
Vehicles Built Up To 03/2002
The SRS uses up to six impact sensors. Within the RCM can be up to two safing sensors which are not separately serviced. The RCM will always have at least one safing sensor for front impact. One more safing sensor is used if the vehicle is equipped with side air curtain modules. The RCM is mounted to the center tunnel beneath the console. In addition, if the vehicle is side impact protection equipped, there are four additional side impact sensors. The four additional sensors are located at the base of each B-pillar and C-pillar. The LH and RH C-pillar mounted side impact sensors are not interchangeable. Mounting orientation is critical for correct operation of all impact sensors.
Vehicles Built 03/2002 Onward
For these vehicles, the SRS uses up to eight sensors. Within the RCM can be up to three safing sensors which are not separately serviced. The RCM will always have at least one safing sensor for front impact. Two more safing sensors are used if the vehicle is equipped with safety canopy modules. The RCM is mounted to the center tunnel beneath the console. All vehicles will have a front impact severity sensor and it is located in the front-center of the vehicle, mounted under the lower radiator support. If the vehicle is equipped with safety canopies, there are four additional side impact sensors. The four additional sensors are located at the base of each B-pillar and C-pillar. The LH and RH C-pillar mounted side impact sensors are not interchangeable. Mounting orientation is critical for correct operation of all impact and rollover sensors.