Second Rowlink
Last updated: October 20, 2023
Overviewlink
The Model Y has two options for second row seating. The first option, a standard five person seating capacity with a driver and passenger seat in the front row and a three passenger bench seat with powered fold-flat backrests in the rear. The rear seats are also capable of reclining. There is also a second option for seven person seating capacity with a driver and passenger seat in the front row, a three passenger bench seat (with the capability to slide and pivot forward) and a two person seating capacity third row.
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| Second Row Seats |
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| 1. Cover 2. Foam/Pad 3. Cushion Pan and Backrest Shell 4. Frame 5. Back panel |
| Second Row Seats |
The seat sections are referred to as 40% (right-side rear seat), 60% (left-side and middle rear passenger seats), and 20% (middle rear passenger seat).
Coverslink
Component Descriptionlink
Model Y seats are available in both white and black Polyurethane (PUR). This material is a leather alternative. When surfaces of the seat back contact one another, one side is a cloth material, while the other side is PUR. This is to reduce noise issues that are typical when PUR rubs against itself.
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| 1. PUR 2. Cloth |
| Second Row Seat Cover |
Theory of Operationlink
Model Y second row seat covers are secured to the foam with a combination of hog rings and hook-and-loop fastening strips. Then sandwiching the foam, the cover is attached to the upholstery support allowing the seatback to maintain shape prior to attachment to the seat frame. There is also stitch detailing within the seat to help form the shape around the foam.
Serviceabilitylink
Cleaninglink
Cleaning PUR seats with some conventional cleaners (especially alcohol-based) can cause performance and appearance degradation. Do NOT use products containing bleach (sodium hypochlorite). It is therefore important to clean seats with only approved cleaners. Below is a list of approved cleaners:
- Clorox NON Bleach Disinfecting Wipes
- Formula 409
- Seventh Generation NON Bleach Disinfecting Wipes
For White PUR ONLY, isopropyl alcohol is the strongest solvent that can be used without damaging the seat material. Moisten a soft cloth with warm water and isopropyl alcohol and gently wipe the stain in a circular motion.
Warning
Isopropyl alcohol should not be used on Black PUR.
Servicing Coverslink
Hog rings must be installed using hog ring pliers to crimp the ring in order to securely fasten it the cover to the foam. Hog rings are a consumable part, as with every removal they need to be cut. Craftsmanship is extremely important when dealing with installing covers to ensure that there are no wrinkles or puckers in the material.
Foam/Padlink
Component Descriptionlink
The seat foam, also referred to as the seat pad provides comfort and stability to occupants.
Serviceabilitylink
If the seat foam and covers have not been installed appropriately it can feel or look as if the seat is missing foam or that the foam has collapsed. Because the foam is sandwiched between the cover and upholstery support, it is possible that it could have been misaligned during install. In some rare cases, the way in which a customer ingresses or egresses from the vehicle can apply pressure on the outmost edge of the cover and foam, causing the foam to get caught on the upholstery support and not maintain it's full shape. This can be resolved by refitting the cover and foam.
Seat Heatlink
Component Descriptionlink
Model Y second row has heating elements in each of the cushion seating positions. The back rest only has heating elements in the left and right seat backs. The center seat, 20%, has an arm rest as the seat back which does not have a heating element.
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| 1. Backrest seat heater mat (x2) 2. Seat cushion heater mat (x3) |
| Second Row Seat Heat |
The seat heater is made up of the following components:
- High side driver
- Pulse Width Modulation (PWM)
- Negative Temperature Coefficient (NTC) thermistors
- Resistive pad
The heating element, or resistive pad, is located only in the center panels of the seat back and seat cushion, the heating element is not located in the side bolsters.
Theory of Operationlink
There are 3 heating temperature targets for the seats (low, medium and high). Target temperatures for both the cushion and the backrest are:
- Low (Setting 1): 28C or 82F
- Medium (Setting 2): 44C or 111F
- High (Setting 3): 60C or 140F
The seat heaters utilize PWM at 1Hz in order to reach the desired target temperature. This means pulsing the voltage at a controlled frequency. The duty cycle (width of the pulses) will be increased if the temperature read by the NTC is below the target temperature, the duty cycle can be increased all the way up to 100%, providing up to 16V. When the temperature read by the NTC is higher than the target temperature, the duty cycle can be decreased all the way to 0% providing no voltage. Due to this PWM, the voltage at the seat heater is constantly changing and varies due to ambient temperature and heat setting level.
Current travels through the resistive pad generating the heat. This resistance remains constant with a functioning seat heater.
The NTC is located only in the seat cushion, not the seat back. It is connected to 5V through a resistor on the body controller. As the temperature of the seat increases, the resistance on the NTC lowers and the voltage read at the controller goes down. If the thermistor is disconnected, the voltmeter will read 5V or 0V depending on where the disconnect occurs. At around room temperature, the voltage at the NTC should be around 3.6V.
Communicationlink
The seat heater communicates via vehicle bus (VEH). The seat cushion and the 60% seat back is controlled by the left-side vehicle controller (VCLEFT). The seat back fo the 40% seat is controlled by the right-side vehicle controller (VCRIGHT). Below illustrates which seat heater positions communicate on which vehicle controller.
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| Model Y Seat Heat Communication |
Serviceabilitylink
The seat heater resistive pad is integrated into the seat cover and is therefore not serviceable.
The temperature felt at the surface of the seat, depends on an occupant sitting in the seat. Compressing the foam and trim with an occupant sitting in the seat allows for the occupant to fully feel the temperature provided by the seat. Factors such as a heat soaked interior, body heat from someone sitting in the seat, direct sunlight and ambient air temperatures can play a big role on the temperature readings at the surface of the seat cover.
Occupancy Sensinglink
Component Descriptionlink
Each seat in the second row contains an occupancy sensor, resistive pad, also referred to as the seat belt reminder (SBR). The occupancy sensors are located in the seat cushion. The occupancy sensors are switches distributed throughout the cushion connected in both parallel and series.
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| Restive Pad (x3) |
Theory of Operationlink
Occupancy sensing for the second row communicates to VCLEFT. The sensor itself is a simple resistive pad that can be tested with a multimeter. Occupied, the resistance should read 1kOhm. Unoccupied, the resistance should read 11kOhm.
Serviceabilitylink
Having the sensors distributed throughout the cushion helps to prevent situations where small items might trigger the seat belt reminder indicator. At the time of publishing this document, the resistive pad, or seat belt reminder, located in the second row cushion is not a serviceable component. This is due to the infrequency of which this part needs to be replaced as well as current production capability.
Framelink
Component Descriptionlink
The second row is comprised of two separate frames. The 60% and the 40%. The 40% contains the right hand second row passenger and the 60% contains the left hand and center passenger positions, with the center position being referred to as the 20%. For Model Y, these structures are stand alone frames with the seat cushion bench being one piece that sits atop the frame.
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| Exploded Second Row |
Theory of Operationlink
The frame allows for movement in the backrest to both fold flat and comfort adjust into 1 of 5 reclined backrest positions. For 5 seat interior, the seat base is stationary and bolts to the vehicle body.
The 7 seat interior frame for the second row is intended to slide forward and backward along the tracks. There is 310mm of total travel along the track for the second row. The track travel is split up into two sections. Comfort zone, which is the rearmost 150mm and Easy Entry which is the forwardmost 160mm. These various track zones allow for different features to occur along the track.
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| 1. EZ Entry Zone 2. Comfort Zone |
| Track Zones |
Serviceabilitylink
A spring is located on the outboard side of the seat, at the axis of rotation for the seatback to fold forward. This spring helps propel the seatback into a folded position, so that a customer does not need to interact with the seat. There are various reasons this dump functionality can not be completed as intended (Discussed further in Dump/Serviceability). The spring attached to the frame should be the last potential root cause to be checked for dump issues. Either the spring itself is not situated properly, or in early life models the spring was not strong enough to overcome the weight of the seatback (typically seen on the 60%). Because the frame is a moving part, it can be the culprit to some noise issues, in these instances be sure to check all mating points to the body as well as the hinge point (axis of rotation).
Comfort Zonelink
Feature Descriptionlink
Adjustments in the comfort zone occur by utilizing the towel bar located at the front of the seat frame, underneath the cushion. The seat can slide fore / aft in 10mm increments by lifting up on the towel bar and sliding the seat using user power.
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| Towel Bar |
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| 1. EZ Entry Zone 2. Comfort Zone |
| Track Zones |
Theory of Operationlink
Pulling up on the towel bar, pushes down the track release lever (a part of the upper track).
The track release lever pushes down on the push pin in order to disengage the tooth plate from the lower track, allowing the seat to move forward and backward within comfort zone.
There is a comfort stopper located on both the left and right upper tracks that moves with the seat base. This comfort stopper will make contact with comfort stopper bracket located on the lower track. This prevents the seat from moving out of the comfort zone, into the Easy Entry zone.
Trim/Plasticslink
Component Descriptionlink
To limit confusion during diagnosis and when talking about the seats, trim is defined as the hard plastic parts on the seat. Seat pads and covers (the textile or leather seat material) is considered seat upholstery and should be referred to as such.
Front facing trim is identified in the image below:
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| 1. Fold flat and comfort recline electrical switch 2. Center escutcheon bezel 3. Rear seat console closeout panel 4. Rear seat closeout cup holder liner 5. Rear seat closeout cup holder floor |
| Seat Trim / Plastics |
In addition to the components shown in the image above, the following pieces are also considered:
- Cushion pan / backrest shell
- Back panels
- B-Covers
- Switches
- Cushion seat side shield
- Only available in the 7 seat option
- Escutcheon
Theory of Operationlink
Cushion Pan / Backrest Shelllink
The Model Y second row seats keep shape with the help of the plastic components that support the foam. The cushion pan and the backrest shell allow for the seat cover, pad, seat heater and occupancy sensors to form one assembly that can be easily removed and replaced. For 7 seat interior, the cushion pan is the mounting point for all the second row actuators, except for the 20% recliner actuator.
Back Panelslink
The back panels for the second row are plastic components that conceal the wiring harness and backrest shell. The back panels also have a cut outs for child seat tethers. Removing the back panel will allow access to inspect some of the recliner mechanism for first steps of investigation.
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| Back Panels |
B-Coverslink
B- covers are the plastic components that cover the recliner mechanism. This is an entirely cosmetic component as it's function is to insure that no parts of the frame are visible to the customer in any of the seating positions. Because B-Covers are located around moving parts there is potential if installed incorrectly or issues with manufacturing, that the B-Cover can cut or tear into the seat cover. Each portion of the frame the B-Cover conceals is made up of an inner and outer B-Cover in order to fully encompass the frame from being visible with the seatback in various positions.
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| 1. 40 B-Cover Inboard 2. 60 B-Cover Inboard 3. 60 B-Cover Center |
| B-Covers |
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| 1. B-Cover Inner 2. B-Cover Outer |
| B-Cover Details |
Switcheslink
For the 5 seat interior option, the shoulder switch releases the recliner mechanism allowing the seat to fold flat or recliner in various positions.
For the 7 seat interior option, the shoulder switch triggers the EZ entry feature, sliding and pitching the seat forward.
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| 1. Shoulder switches 2. Cushion seat side shield switch (7 seat interior only) |
| Switches |
Cushion seat side shield (7 seat interior only)link
The cushion seat side shield is both a cosmetic and functional component. Cosmetically, it covers the tracks and gear mechanisms that put the allow the seat to move. Functionally, the cushion seat side shield has an electrical switch that communicates on VCLEFT for 60% and VCRIGHT for 40%. This switch controls the functionality of the recliner actuator. When the switch is held, the backrest can be adjusted into 1 of 5 positions for comfort adjust. When the switch is triggered momentarily, the backrest will dump forward into the fold flat position.
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| Cushion Seat Side Shield |
Escutcheonlink
The escutcheon is the plastic bezel in which the center seat belt feeds through the backrest. The center seatbelt is the only retractor incorporated into the second row and the escutcheon acts as protection to the cover.
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| Escutcheon |
Actuatorslink
Component Descriptionlink
Model Y has a different number of actuators in the seat depending on whether the 5 seat or 7 seat option was chosen. The 5 seat option includes only the recliner actuator. The 7 seat option includes recliner, floor latch, and Easy Entry track actuators.The actuators for 7 seat option are located on the cushion pan.
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| 1. Recliner Actuators 2. Floor Latch Actuators 3. Track EZ Entry Actuators |
| Actuators |
Theory of Operationlink
Recliner Actuatorlink
The recliner actuators are utilized in both 5 and 7 seat interior. There are 3 recliner actuators located in the second row. For the left and right seating positions they release the locking mechanism of the recliner so that the backrest can either adjust or fold flat. For the center seating position, or the 20% seat, the recliner actuator releases the latch located on the 20% seatback allowing it to fold flat independently of the 60% seat.
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| Recliner Actuators |
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| 20% Latch |
Floor Latch Actuatorlink
The 7 seat interior has floor latch actuators in both the 40% and 60%. The floor latch actuator moves the floor latches on both the inboard and outboard track to the open position, allowing the seat to pop up off the floor.
Easy Entry Track Actuatorlink
The 7 seat interior has Easy Entry track actuators in both the 40% and 60%. The Easy Entry track actuator sets off a series of gear mechanisms that allow the seat to move forward and backward along the track. They are as follows:
- The track pin disengages the track lock plate
- The comfort stopper lever is moved out of the way, allowing for the seat to travel out of comfort zone and into Easy Entry zone.
- The Easy Entry wheel bracket moves up to allow it roll along the lower track, which will keep this gear mechanism in a position that keeps the track unlocked. With this mechanism properly in the unlatched position, the Easy Entry track actuator can de-energize
Serviceabilitylink
The second row seat actuators cannot be replaced without replacing the entire seat assembly.
Dump Functionlink
Feature Descriptionlink
As mentioned earlier, the Model Y second row seat has a "dump" functionality. When the recliner actuator has actuated to release the seatback latch, the seatback spring then propels the seatback forward in order to dump the seat.
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| Frame Clock Spring |
Theory of Operationlink
The second row dump function is defined as the ability of the seat back to spring forward when only the shoulder switch or trunk switch is utilized and with no interaction from a user to fold the seat back down. The Model Y only has dump functionality on the 60% and 40% seat backs. The 20% seat back is not intended to dump forward, the 20% is merely a "pass thru" for large items in the vehicle.
Serviceabilitylink
There are various reasons the dump functionality may not be occurring.
- Issue with the spring overcoming the weight of the seatback.
- Friction between the 40% and 20% seat back (this can be tested by laying the 20% seatback down to eliminate unnecessary friction).
- Friction between the bottom of the seatback and the top of the seat cushion, or in the case of the 20%, friction between the lumbar bun and the armrest.
- The pivot clamps on the 20% armrest being too tight, restricting the axis of rotation.
- The latch does not release fully.
Fold Flat Functionlink
Feature Descriptionlink
Fold flat is referred to the position in which the seatback is completely folded down and laying on top of the seat cushion. Fold flat can occur on the 40%, 60% and on the 20%. When the 20% is folded down independently of the 60% it creates a pass through intended for large item storage.
Theory of Operationlink
The foam/pad of the seat cushion should have enough support on the side bolsters to keep the seatback from resting on the middle portion of the seat cushion where the occupancy switch lies. With the seats folded flat, the occupancy sensor should remain in the EMPTY state.
A short press of an electrical switch causes the actuator to run full stroke. The electrical switch for this feature can be found in these locations:
- The rear compartment.
- The outboard shoulder of the rear seat - only available on the 5 seat interior.
- The seat cushion side shield - only available on the 7 seat interior.
After the short press, there is an in-rush current spike and shortly after, a stall current spike as the actuator hits the travel limit. When the actuator has reached the travel limit, the seat back is sprung forward into the fold flat position due to the spring located at the seat back hinge point. When the switch is released, and the actuator is de-energized, the actuator is spring returned back into the extended state allowing the seat back to lock into the next available position.
Fold Flat Switch - Rear Compartmentlink
To fold flat the second row seat backs by using an interior button in the trunk, there are two window switch like buttons in the rear that can trigger either the 40% or 60% to fold flat. It sends the same signal to VCLEFT that is sent when pressing the switch in the outboard shoulders or the cushion side shield. This trunk switch utilizes one input with a voltage divider to indicate which of the seat positions needs to fold flat.
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| Interior fold flat switch |
Fold Flat Switch - Outboard Shoulderlink
The 60% and 40% sides can be adjusted via the electrical switch on the shoulders of either side, these switches can fold the seat back flat or adjust the seatback into various positions.
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| Outboard shoulder switches |
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| 60% fold flat |
Fold Flat Switch - Cushion Side Shield (7 Seat Interior Option Only)link
The 60% and 40% sides can be adjusted via the electrical switch on the seat cushion side shield on either side, these switches can fold the seat back flat or adjust the seatback into various positions.
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| 7 seat interior seat cushion side shield button |
20% Fold Flat Functionlink
When pressing on the back panel switch on the 20% seat back, the recliner actuator pulls on a latch to the open position and can then be laid flat. The striker for the 20% latch is attached to the leftmost seat.
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| 20% fold flat switch |
Below illustrates the center seat (20%) folded down, to allow customers to carry long items such as skis.
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| 20% fold flat |
Serviceabilitylink
When folding flat, there is a potential that the seatback can make contact with the rear load floor.Interaction between the seatback and the load floor can cause creasing in either the load floor or seatback panel.
Comfort Adjustlink
Feature Descriptionlink
Comfort adjust can occur on the 40% or the 60% side but cannot happen on the 20% individually. Comfort Adjust refers to moving the second row seat backrest to 1 of 5 positions. Due to the weight of the seatbacks, the preferred method of locking the seatback into riding position would be to adjust it from the side door as opposed to reaching from the rear trunk. Adjusting from the side door gives the user more control and ease of operation of the seatback.
Theory of Operationlink
5 seat interior
The outboard shoulder switch must be held while the user finds the desired seat back angle. There is a 10-degree range of comfort adjust, provided in 2-degree increments. When the switch is released, the seat back locks at the nearest locking position.
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| Outboard shoulder switches |
7 seat interior
The seat cushion side shield button must be held, while the user finds the desire seat back angle. There is a 10-degree range of comfort adjust, provided in 2-degree increments When the switch is released the seat back locks at the nearest locking position.
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| 7 seat interior seat cushion side shield button |
For 5 and 7 seat interior options, when the button is held, a signal is communicated to VCLEFT for 60% or VCRIGHT for 40%. The recliner actuator then energizes pulling on the recliner release arm. This release arm, on the 60%, is welded to both the 20% pivot shaft and the recliner disc. For the 40% this release arm is only integrated into the recliner disc.
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| Recliner Mechanism, 60% |
There is a stopper located on the recliner mechanism of the frame that prevents the seatback from reclining too far back.
Serviceabilitylink
The seatbacks could be misaligned from one another, with one seat sitting slightly more forward than the other. It is important to check the seatback alignment when in the "first lock", the most upright position of the seat back, or in the fully reclined position. This can be caused by an issue with one of the seat frame's recliner disc weld, the disc could be welded in an inappropriate position or a potential bent stopper.
Easy Entrylink
Feature Descriptionlink
Easy Entry is when the second row seat slides forward and pitches out of the way to allow access to the third row seats. This option is only available on Model Y vehicles with 7 seat interior.
Easy Entry is not allowed if vehicle is in the DRIVE state. Occupant, buckle, and door status have no effect on the usage of Easy Entry. The backrest cannot fold flat while the Easy Entry cycle has begun. In the event that the side shield switch or trunk switch is pressed at the exact same time as the shoulder switch, the shoulder switch will complete it's action first.
Theory of Operationlink
Easy entry occurs with the following sequence of events:
- The Easy Entry switch (shoulder switch) is enabled (pressed for more than 100ms).
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The track Easy Entry actuator releases the track lock on both the inboard and outboard tracks.
- This allows for linear motion forward and backward along the track.
- This allows for linear motion forward and backward along the track.
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Customer must provide the effort to slide the seat forward along the tracks and move the seat from the comfort zone to the Easy Entry zone
- The customer has 3.5 seconds to move the seat from comfort zone to Easy Entry, if the seat has not reached Easy Entry zone in 3.5 seconds, the track will re-lock.
- When the seat has reached the Easy Entry zone, the floor latch actuator is activated and disengages the floor latch on both inboard and outboard tracks. This allows the seat to pivot forward.
- The customer pushes the seat forward with the help an Easy Entry torsional spring (located at the front of the seat frame) which is intended to help the seat pop up into Easy Entry position.
- Once in the fully pitched position, a mechanical interlock located on the track falls into place and forces the seat to stay in the full upward pitched position. This keeps the seat pitched until the seat is slid backward out of the Easy Entry zone.
The comfort and Easy Entry zones mentioned above are indicated by a seat track position sensor (STPS), located on the inboard seat track.
| Value | Meaning |
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| LOW | Rearward of the STPS is the comfort zone |
| HIGH | Forward of the STPS is the Easy Entry zone |
The Easy Entry Cycle state has the following values:
| Value | Meaning |
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| inactive | Seat is in comfort zone |
| active | Seat is out of comfort zone and Easy Entry switch is ENABLED |
| pitched | Easy Entry cycle is ACTIVE and Floor Latch Hall sensor is HIGH |
The left and right floor latches have Hall Effect sensors with the following readings:
| Value | Meaning |
|---|---|
| LOW | the seat is still latched to the floor |
| HIGH | the seat is no longer latched to the floor |
Serviceabilitylink
When the seat is released from the floor, the Easy Entry torsional spring aids the seat in pitching forward. This spring force aids in lifting the seat, but also works against the customer as they try to secure the seat back on the floor. This torsional spring should be the first place to check if a customer complains of difficulty getting the seat to pop up or lock on the floor.