# Restraint System

## Overview

### Component Location

1. Front crash sensors

2. Knee airbag - RH

3. Passenger airbag

4. Pressure sensor (PS) - RH

5. Side curtain airbag - RH

6. Seat belt retractor pre-tensioner - RH

7. ‘B’ pillar crash sensor - RH

8. Side airbag - RH seat

9. ‘C’ pillar crash sensor - RH

10. Side curtain airbag - LH

11. ‘C’ pillar crash sensor - LH

12. Side airbag - LH seat

13. ‘B’ pillar crash sensor - LH

14. Seat belt retractor pre-tensioner - LH

15. Driver seat sensor

16. Seat belt buckle - LH

17. Seat belt buckle - RH

18. Driver airbag

19. Knee airbag - LH

20. Passive Safety Restraints Control Module (PSRCM)

### General

Model S is equipped with a Tesla Supplementary Restraint System (TSRS). The system comprises the following components:

- Passive safety restraint control module (PSRCM)

- Multiple crash sensors

- Driver and passenger dual-stage front airbags

- Driver and passenger knee bolster airbags

- Driver and passenger seat side (pelvis/torso) airbags

- Driver and passenger seat belt pre-tensioners

- First and second row side curtain airbags

- Occupant classification system (OCS) - North American market only

- Seat belt reminder switches

- Pyrotechnic fuse

- Collapsible steering column

The TSRS is designed to work in conjunction with the seat belts. These devices supplement, but DO NOT replace, the protection afforded by the seat belts. Seat belts are proven to be the single most effective safety device in a car, and should always be worn. Properly worn seat belts also ensure that the occupant is seated in the optimum position to benefit from the full effectiveness of the airbags and seat belt pre-tensioners.

The first row safety restraints feature shoulder and lap belt pyrotechnic pre-tensioners, dual-stage front airbags, seat side airbags, and knee bolster airbags to protect each occupant. In North American market cars, the passenger seat has an advanced occupant classification system (OCS) that can adapt or inhibit airbag deployment based on occupant size or detection of a child seat (among other parameters, such as an empty seat). The first and outboard second row occupants are protected by side curtain airbags that deploy from the roof rails. The collapsible steering column plays a role in occupant safety as well, by absorbing the energy of the driver’s upper body during a frontal collision.

In the event of a collision, the pyrotechnic fuse deploys to isolate high voltage to the HV Battery. All high voltage is therefore removed from all cabling, the DC/DC converter, the HV junction box, the cabin HVAC system, etc.

The TSRS is designed to deploy in select moderate-to-severe front, side, and rear impacts, as well as rollovers. When the PSRCM detects an impact that warrants deployment, the seat belt pre-tensioners and pyrotechnic fuse are always triggered. Whether any airbags are deployed, and which ones are deployed, depends on the type and severity of the impact.

- Moderate frontal impact: Pyrotechnic fuse, all pre-tensioners, knee airbags, and front upper body stage 1 airbags only. In this case, stage 2 automatically goes to disposal (100 ms after stage 1) so that it is safe for first responders and service personnel. Note that NO side airbags are deployed, as they are reserved for any secondary side impact. If a child booster seat or rear-facing infant seat is detected in the front passenger seat, the front passenger upper body airbag is disabled.

- Severe frontal impact: Same as moderate, but front upper body airbags deploy both stage 1 and stage 2 for maximum effect. If a child booster seat or rear-facing infant seat is detected in the front passenger seat, the front passenger upper body airbag is disabled. Also, if the OCS determines that the occupant is too small for stage 2, it is limited to stage 1.

- Side impact: Pyrotechnic fuse, all pre-tensioners, seat side airbags, and curtain airbags. Note that NO front airbags are deployed, as they are reserved for any secondary frontal impact.

- Rear impact: Only pyrotechnic fuse and seatbelt pre-tensioners are deployed. NO airbags are deployed.

- Rollover: Pyrotechnic fuse, all pre-tensioners, and seat side and curtain airbags are deployed (no frontal airbags are deployed).

Crash Type | Pre- tensioners | Front Stage 1 | Front Stage 2 | Knee Bolster | Seat Side | Side Curtain | Pyro Fuse
--- | --- | --- | --- | --- | --- | --- | ---
Front, moderate | X | X |  | X | 1 | 1 | X
Front, severe | X | X | X | X | 1 | 1 | X
Side | X | 2 | 2 | 2 | X | X | X
Rear | X |  |  |  |  |  | X
Rollover | X |  |  |  | X | X | X

X = deploy

1 = reserved in case of side impact

2 = reserved in case of rear impact

Although the airbags and pre-tensioners are designed to be triggered electrically, they are pyrotechnic devices and could deploy unexpectedly— even when not connected to an electrical source— if proper transport, storage, and handling methods are not followed. Always follow Service Manual procedures when diagnosing or repairing the TSRS. Only use Tesla-approved equipment to intentionally deploy a pyrotechnic device for disposal purposes.

WARNING: Accidental deployment can cause damage and personal injury. Always refer to the Owner Information for correct use of the TSRS and seat belt systems, and to the Service Manual for correct fitment, repair, and disposal of system components.

## Component Descriptions

### Passive Safety Restraint Control Module (PSRCM)

1. PSRCM

The TSRS is controlled by the Passive Safety Restraint Control Module (PSRCM), which includes fault detection and warning circuits. If a fault is detected, an indicator light in the instrument panel notifies the driver. Diagnostic Trouble Codes (DTCs) are also retrievable using Toolbox.

The PSRCM is calibrated specifically to the vehicle model. It contains accelerometers to measure forces acting on the vehicle, and circuits for monitoring the resistance, and therefore condition, of all deployment loops and pyrotechnic devices. It is the primary device that commands the deployment of all TSRS components.

In the event of a collision, the PSRCM compares the signals from the crash and pressure sensors to pre-calibrated values stored in memory. When the generated signals exceed the pre-calibrated values, the PSRCM directs current through the appropriate deployment loops to deploy the airbags, pre-tensioners, and pyrotechnic fuse as necessary, depending on the severity of the impact. The PSRCM records certain aspects of the event data when a deployment occurs and displays the AIRBAG indicator located in the instrument panel.

When deployment occurs, the PSRCM sends a collision detection CAN message to the body controller to switch on the interior and hazard lights and unlock all doors and the trunk.

The PSRCM performs continuous diagnostic monitoring of the TSRS system electrical components and circuitry when the vehicle is turned on. A safing sensor within the module provides an electro-mechanical switch as a safety backup to the accelerometer circuit.

If the PSRCM detects a malfunction, a DTC is stored and the PSRCM requests the instrument cluster to display the AIRBAG indicator, notifying the driver that a malfunction exists. If positive voltage is lost during a collision, the PSRCM maintains a 23 volt reserve loop for airbag deployment.

NOTE: Service or rescue operations must allow 1 minute for the 23 volt reserve loop to dissipate when disabling the TSRS system.

### Pyrotechnic Fuse

1. 12 volt battery

2. Battery fusebox

3. Pyrotechnic fuse F93

The pyrotechnic fuse F93 is located on the battery fusebox. The PSRCM fires the fuse anytime the airbags and/or pre-tensioners deploy. This isolates high voltage to the HV Battery, which makes the vehicle safe for the occupants and emergency responders if the high voltage system is compromised by collision damage.

### Airbags

WARNING: Airbags inflate with great force, in a fraction of a second. A vehicle occupant could be seriously injured or even killed if sitting closer than 10 in (255 mm) to the airbag, or if seated incorrectly. Do not place any objects in the path of airbag deployment (such as on top of the passenger side instrument panel).

Airbags consist of a housing, an inflatable airbag, two initiating devices for dual front airbags, and a canister containing gas generating material.

The driver and passenger upper body airbags have two stages of deployment, which varies the amount of restraint to the occupant according to the severity of the collision. For moderate frontal collisions, the airbags deploy at less than full deployment, or stage 1 of the airbag. For more severe frontal collisions, a full airbag deployment (both stage 1 and stage 2) is initiated. The current passing through the airbags ignites the material in the canister, producing a rapid generation of gas. The gas produced from this reaction rapidly inflates the airbag. Once the airbag is inflated, it quickly deflates through the airbag vent holes and/or the airbag fabric.

When the crash sensors detect a collision, the PSRCM processes the information provided to support airbag and pre-tensioner deployment. The PSRCM contains a sensing device that converts changes in vehicle speed to an electrical signal and compares these signals to values stored in memory. If the signals exceed a stored value, the PSRCM determines the type and severity of the impact, sending current through the appropriate deployment loops. The PSRCM deploys the airbags and pre-tensioners if it detects a collision of sufficient force. If the force of the impact is not sufficient to warrant dual-stage airbag deployment, the PSRCM may still deploy the stage one airbags and the seat belt pre-tensioners.

The pre-tensioners are never deployed without the airbags operating.

The PSRCM performs continuous diagnostic monitoring of TSRS system electrical components and deployment loops for malfunctions, and displays the TSRS indicator light if a fault is detected.

Upon detection of a circuit malfunction, the PSRCM sets a DTC and informs the driver by displaying the TSRS system AIRBAG indicator in the instrument cluster.

#### Driver Front Airbag

1. Steering wheel

2. Driver front airbag

Mounted on the steering wheel, the driver airbag is a dual stage front airbag that provides protection from impact with the steering wheel and the surrounding dashboard for adults of all sizes.

#### Passenger Front Airbag

1. Passenger front airbag

The passenger front airbag is mounted under the instrument panel on the front passenger side. Similar to the driver, the passenger front airbag is dual stage. The passenger airbag provides protection for occupants based on their size as calculated by the Occupant Classification System (OCS). If the seat is empty, the occupant is determined as too small, or a child seat is detected, the airbag does not deploy.

#### Front Seat Side Airbag

1. Side airbag (front row outboard)

The side airbags are part of the front seats. The seat side airbags are deployed from the outboard side of the seat, forming a cushion between the occupant and the door, protecting the occupant’s upper torso and pelvis area during a side impact.

#### Side Curtain Airbags

1. Side curtain airbag

The side curtain airbags are located near the side roof rails. They inflate over the full area of the front and rear side windows to form a cushion, protecting the occupant’s head from contact with the window frame or pillar(s) in a side-impact collision. The side curtain airbag deploys downwards from the top and drapes over the entire glass area. The side curtain airbags stay inflated for a few seconds after a collision in case the vehicle rolls over.

#### Knee Airbag

1. Knee airbag

Knee airbags for the driver and front passenger are located on the lower part of their respective dashboards and are designed to deploy against the occupant’s lower legs, reducing the forward momentum of the lower body during a mid- to high-speed frontal impact. Driver side deployment is dependent on the logic determined by the PSRCM, and passenger side deployment is dependent on the logic determined by the OCS and the PSRCM. When deployed, the knee airbag pushes against the occupant's lower legs, contacting them at the knee cap level, cushioning the legs down to the shin and ankle level. This holds the occupant properly positioned in the seat.

### Steering Column

1. Steering column carrier

2. Tilt motor

3. Telescopic motor

4. Steering shaft

5. Collapse track

The steering column is designed to absorb energy and collapse during frontal collisions, in order to decrease the chance of injury to the driver. The column has 100mm of collapsible travel. A deformable wire adds resistance to the collapsing motion. If the vehicle has been in a collision that caused driver airbag deployment, the column should be inspected to check whether it collapsed.

WARNING: The steering column must be inspected whenever the driver airbag has deployed. Refer to BR-14-20-001 for inspection instructions.

### Clockspring

1. Steering column control module

2. Clockspring

The clockspring is encapsulated into a plastic cassette, contained within the Steering Column Control Module (SCCM). The cassette consists of an outer and inner housing, with integral connectors that contain a flat ribbon flexible cable with four wires carrying out the following functions:

- Positive feed to the inflator module, stage 1 and 2

- Ground to the inflator module, stage 1 and 2

### Airbag Indicator Light

1. Airbag indicator light

2. Front seat belt indicator light

The airbag indicator light, located in the instrument cluster, is used to notify the driver of TSRS system malfunctions and to verify that the PSRCM is communicating with the instrument cluster. When the vehicle is on and drive rail power is on, the PSRCM is supplied with positive voltage. The instrument cluster momentarily turns on the airbag indicator light. While the indicator is on, the PSRCM conducts tests on all TSRS system components and circuits. If no malfunctions are detected, the PSRCM communicates with the instrument cluster and switches the airbag indicator OFF.

A TSRS system malfunction could result in non-deployment of the airbags or deployment in conditions less severe than intended. The TSRS system airbag indicator remains ON until the malfunction has been repaired.

### Seat Position Sensor

1. Seat position sensor

The seat position sensor (SPS) is used to determine the distance between the driver seat and the steering column. Information from the SPS allows the PSRCM to disable stage 2 of the airbag if the seat is forward of a pre-determined point in seat track travel (closer to the airbag module). The SPS is a Hall effect sensor, mounted on the outboard seat track of the driver seat. The seat track includes a metal bracket that shunts the SPS magnetic circuit, creating two states of seat position. The shunted state represents a rearward seat position. The non-shunted state represents a forward position. These 2 states are inputs to the PSRCM.

When an SPS informs the PSRCM that the state 1 threshold is reached (seat is rearward), the PSRCM does not disable stage 2. When the state 2 threshold is reached (seat is forward), the PSRCM disables stage 2 deployment of the driver airbag.

NOTE: Stage 2 deployment is also disabled if the PSRCM detects that the sensor is faulty.

The sensor is secured to the seat track with two rivets.

### Seat Belt Pre-Tensioner — First Row Seats Only

1. Lap belt pre-tensioner

2. Shoulder belt retractor and pre-tensioner

3. Seat belt buckle

The driver and first row passenger seat belt pre-tensioners are a dual pre-tensioner system. The lap belt pre-tensioners are mounted on the body sill side, and the shoulder belt pre-tensioners are integral with the retractors. The initiators of both pre-tensioners are part of the seat belt pre-tensioner deployment loop and always deploy simultaneously.

Anytime an airbag deployment occurs, the seat belt pre-tensioners are also deployed. The PSRCM directs current through the deployment loops to the initiator. Current passing through the initiator ignites the material in the canister, producing a rapid generation of gas. The gas produced from this reaction deploys the seat belt pre-tensioners, which remove slack in the lap and shoulder belts.

### Crash Sensors

1. Crash sensor - accelerometer type

Eight crash sensors are fitted to the Model S. They are either accelerometer type sensors or pressure sensors, and are fitted in the following positions:

- Front bumper carrier sensors (x2) - accelerometers

- ‘B’ pillar sensors (x2) - accelerometers

- ‘C’ pillar sensors (x2) - accelerometers

- Front door sensors (x2) - pressure sensors

The accelerometer type crash sensors contain a sensing device that monitors vehicle acceleration to detect collisions that are severe enough to warrant airbag deployment. The crash sensors are not part of the deployment loop, but instead provide input to the PSRCM. The PSRCM contains a microprocessor that performs calculations using the measured accelerations and compares these calculations to a value stored in memory. When the calculations exceed the stored value, the PSRCM directs current through the deployment loops, deploying the appropriate airbags and the seat belt pre-tensioners.

1. Crash sensor - Pressure type

The Piezo-electric pressure sensors mounted inside the front LH and RH doors measure the dynamic pressure change caused by deformation of the door in a side crash. The measuring range is 0.5 bar to 1.35 bar.

The inputs from the pressure sensors are processed by the PSRCM to deploy the side airbags and the seat belt pre-tensioners.

NOTE: It is extremely important to always reinstall or replace any plugs or tape removed from the door shells when servicing components inside the door. The pressure sensors are precisely calibrated to respond to pressure changes within the door in the event of a collision. Opening more holes in the door creates more escape paths for air, which diminishes the sensor's ability to accurately detect a side impact, and can negatively affect airbag deployment

### Occupant Classification System (OCS) - Front Passenger Seat Only - USA

1. OCS sensor mat (fluid filled)

2. ECU

The OCS monitors the seated weight and pattern to estimate the type of occupant sitting in the front passenger seat, and communicates the status to the PSRCM using a CAN signal. The PSRCM uses this information to determine whether to enable or suppress the deployment of the front passenger airbag and corresponding knee airbag.

The OCS consists of an electronic control unit (ECU) a sensor mat in the seat, a harness, and a PASSENGER AIRBAG ON/OFF indicator.

The OCS measures the pressure change in the mat fluid (and pattern through cell arrangement) to determine the type of occupant in the front passenger seat. The ECU compares this pressure change to the internally stored threshold to determine whether the seat is occupied, and what size of passenger is detected (see table below). The OCS sends this information to the PSRCM to either disable the front passenger airbag and knee airbag or enable stage 2 of the airbag system.

The PSRCM notifies the occupants of the disable status by displaying the PASSENGER AIRBAG ON/OFF indicator.

If a fault is detected, the OCS sends a message to the PSRCM. The PSRCM responds by sending a command message to the instrument cluster to display the TSRS system AIRBAG indicator.

Front Passenger Seat Occupancy | Telltale
Seat empty | PASS AIRBAG OFF
Infant in child seat (up to 20 lbs) | PASS AIRBAG OFF
Child or small occupant (20-100 lbs) | PASS AIRBAG ON/OFF
Heavy object or occupant | PASS AIRBAG ON

NOTE: Values are approximate. Occupants whose weight is close to the low weight threshold can cause the status to occasionally switch on and off depending on seating position and physique.
NOTE: The Occupant Classification System (OCS) is precisely calibrated for each individual seat at the factory. When servicing the OCS or the Seat Assembly with OCS, Tesla’s service procedures must be followed so that OCS system function is not compromised. Any service performed on the Seat Assembly with OCS must be followed by a Seat Re-Zero procedure.

### Seat Belt Reminder (SBR) Sensors

1. SBR sensor

The SBR sensors are fitted in the seat cushion of the appropriate seat. On USA specification vehicles, it is only fitted in the driver’s seat. On all vehicles, regardless of market, the driver seat SBR switch is an input to the BCM. The BCM sends the state of the sensor to the PSRCM over the CAN bus. The BCM also uses this input for vehicle on/off, gear selection, and parking brake behavior.

SBR sensors are fitted to all five seating positions of the first and second row seats on EU/Asia market vehicles. The SBRs always actuate for 5th percentile occupants and larger, but may actuate for other smaller occupants or objects below this weight. The PSRCM uses this signal, together with information from each seat belt buckle, to display an indicator light and sound an audible warning if an occupant has not fastened a seat belt.

Behavior definitions for EU/Asia markets are pending.

NOTE: On EU and Asia Pacific vehicles, the seat belt warning indicator is on the touchscreen, but the chime operates as described above if a rear seat is occupied with the seat belt unfastened.

## Operation

### Starting and Driving

1. Airbag indicator light

2. Front seat belt indicator light

The airbag warning indicator displays for six seconds when the car is switched on as a system check. After the system check, if there is no active fault, the indicator turns off and stays off. If there is an active fault, the indicator turns off for one second and then turns back on for the remainder of the ignition cycle, or until the fault is no longer active.

The front seat belt indicator and chime are controlled by the PSRCM based on input from the SBR switches and, in the North American market, the OCS. The passenger seat SBR and the OCS are inputs to the PSRCM. The front seat SBR system has three stages of operation for each seat.

- Stage 1: When drive mode is entered, if the seat belt is not fastened, the indicator flashes and the chime sounds for 6 seconds. If the seat belt is fastened or power is turned off, the warning stops within 1 second. If after 6 seconds the seat belt is still not fastened, the indicator stays on solid until the seat belt is fastened, power is turned off, or a transition to stage 2 is reached.

- Stage 2: If the seat belt is not fastened and vehicle speed exceeds 12 mph, the indicator flashes and the chime sounds for 6 seconds, then stops for 2 seconds. This cycle repeats 3 times, then the indicator stays on solid.

- Stage 3: If vehicle speed drops below 12 mph after all chime and indicator cycles have been completed, the PSRCM re-arms stage 2 operation. When vehicle speed again exceeds 12 mph, stage 2 behavior resumes.

If the seat belt is fastened during any of the three stages, the chime stops and the indicator turns off. If the seat belt is fastened and then unfastened during the same power cycle, the PSRCM restarts the sequence from stage 1.