So lately I have been getting a lot of questions about how the system works, or people coming in for thinking it is not working, and wanted to give everyone this info. I came across a great video that explains in laymans terms how it works. I actually learned a few things, and I thought I knew all about it. It's a long read but worth it if you every wanted to know....

This is the transcript of the video, I highlighted a few areas to indicate when the narrator came in to make it easy to read.


Passenger Sensing System

GM's 'Passenger Sensing System' helps GM vehicles comply with Federal Motor Vehicle Safety Standard (FMVSS) 208's advanced air bag requirements. The Passenger Sensing System is designed to help reduce the potential for inflation-induced injuries or fatalities to smaller occupants, including children, who may be seated improperly in front of an air bag. An important message to reinforce with your customers is that even with the Passenger Sensing System GM recommends children be properly secured in a rear seat. This message is in the GM Owner's Manual for every vehicle equipped with the Passenger Sensing System and reinforced on visor labels as well.

Before we review this new system we need to clarify the system's name. In GM's Owner's Manuals, sales and promotional literature, websites and press statements the system is called the 'Passenger Sensing System.' In the service and parts literature the system is called the 'Passenger Presence System.' Both names apply to the same system. Customers may call the technology the 'Passenger Sensing System' or they might call it the 'air bag suppression system.' What does this system do? The Passenger Sensing System uses sensors in the front passenger seat to determine whether to automatically enable, turn on, or disable, turn OFF the front passenger's frontal air bag.

The driver's air bags are not part of the Passenger Sensing System. The Passenger Sensing Systems' sensors gather information related to the occupant's weight or mass and the kind of pressure placed on the seat. This information helps determine whether there may be a smaller occupant sitting in the seat who may be at greater risk of injury from a deploying air bag. GM's Passenger Sensing System is designed to turn the front passenger air bag off if:

The right front passenger seat is unoccupied.

The system determines that an infant in a rear facing infant seat is present.

The system determines that a small child is present in a forward facing child restraint.

The system determines that a small child is present in a booster seat. A smaller person, such as a child who has outgrown child restraints occupies the right front passenger seat.

The right front passenger takes his or her weight off the seat for a period of time.

If there is a critical problem with the air bag system or the Passenger Sensing system.

For some children who have outgrown child restraints and for very small adults, the Passenger Sensing System may or may not turn off the front passenger air bag, depending upon the person's seating posture and body build. All the information we've just discussed is in the GM Owner's Manuals. The Passenger Sensing System is designed to turn the front passenger air bag on if the system senses that a person of adult size is sitting properly in the right front passenger seat. If manufacturers comply with the advanced air bag rule by turning off the front passenger air bag for certain occupants, the system is required to indicate that the air bag is 'off.'

The status indicator that is part of GM's Passenger Sensing System is designed to give customers more complete information. The Passenger Sensing System has a status indicator that will be lit at all times. If the air bag is enabled the indicator says 'Passenger Air Bag ON' or 'Pass Air Bag On.' If the air bag is disabled, the indicator says 'Passenger Air Bag OFF' or 'Pass Air Bag OFF.' GM's status indicator is visible after the driver starts the vehicle. In some vehicles the Passenger Sensing System will also control the front passenger's side impact air bag. The GM Owner's Manual for each vehicle with the Passenger Sensing System identifies which bags are affected by the system. The Owner's Manual also provides other important information about the Passenger Sensing System.

GM currently uses four different Passenger Sensing System technologies developed by four different suppliers. All of these technologies are designed to meet the federal requirements. The four passenger sensing technologies that are currently in GM vehicles are Delphi's PODS-B, Elesys, IEE and Aisin.

Delphi PODS-B

The Delphi PODS-B system uses a silicone filled bladder. The occupant's weight generates a pressure input onto the bladder through the seat cushion. The system doesn't measure all of the occupant's weight because some of the weight is distributed through the occupant's legs and not onto the system's bladder. Tension in the safety belt generates an additional input to the system. The PODS-B control module compares the adjusted weight estimate to a threshold and communicates an air bag ON or OFF decision to the air bag control module. All of GM's 2003 and 2004 model year vehicles that are equipped with a Passenger Sensing System use the PODS-B system with additional implementations of this technology in some 2005 and later models.

Elesys

The Elesys system is a capacitive system which uses flexible sensors to determine the occupant's presence, relative amount of mass and relative position on the seat. The sensors' input is used to help discriminate between a child in a child restraint, a child sitting directly on the seat and an adult-sized occupant sitting directly on the seat. GM first implemented the Elesys system in the 2005 model year on the Buick Lacrosse, with additional implementations beginning in the 2006 model year.

IEE

The IEE system uses an array of Force Sensing Resistor cells located between the seat trim and the top surface of the seat cushion foam. It uses pattern recognition as well as area and load on the seat to communicate the air bag ON or OFF decision to the air bag control module. GM first implemented the IEE system in the 2005 model year on the Cadillac CTS, with additional implementations beginning in the 2006 model year.

Aisin

The Aisin system uses four seat rail mounted sensors that measure the weight of the occupant in the seat. That information is relayed to the air bag control module and used to determine the air bags on/off decision. The Pontiac Vibe began using this system in the 2005 model year. All of these technologies comply with Federal Motor Vehicle Safety Standard 208's requirements. In addition, General Motors and its Passenger Sensing System suppliers have developed a variety of internal considerations that are used to help evaluate system performance.

Passenger Sensing System (PSS) Video

(An older man and his wife are at the write up area talking to the service consultant, the car in the BG.)
Service Consultant: How ya doing?

Man: Good, how about yourself?

Service Consultant: Good, what can I do for you today?

Man: Well, the air bag light is always off. It doesn't seem to matter whether my wife is sitting in the front seat or not. I figured there must be something wrong.

Wife: Isn't it supposed to be on when I sit in the front seat?

Man: I read the Owner's Manual and it says when an adult sized person sits in the front seat the air bag light should change to 'Passenger air bag on'. But that doesn't seem to happen when my wife is in the seat.

Service Consultant: So it never goes to 'Passenger air bag on?' Do you get any other warning lights on the instrument panel? Man: No, no other warning lights but the air bag light has changed to 'Passenger air bag on' a couple of times.

Service Consultant: Can you remember when it changed to air bag on?

Wife: Once I had some library books on my lap so I could hold on to them. The light said 'Passenger air bag on' that time.

Man: And the air bag light comes on when my daughter is in the car with me.

Service Consultant: Is your daughter bigger then your wife?

Man: Well, she's slender like her mother and she is taller.

Service Consultant: Let's take a look at the car.

It's important to remember that the status light indicating the air bag is off doesn't necessarily mean there is a problem with the system, even when an adult occupies the seat. GM developed and tested the Passenger Sensing System to meet federal requirements. FMVSS 208 provides a number of options for automakers who elect to meet the advanced air bag requirements with an automatic air bag suppression system.

For example, manufacturers can confirm their systems meet the federal requirements for enabling, turning on the passenger air bag by using either crash test dummies or human beings. If an automaker uses crash test dummies to validate its suppression system for compliance, FMVSS 208 requires that the system enable or turn on the passenger air bag when the 5th percentile adult female test dummy specified in the standard is seated in the front passenger seat. The standard also specifies the physical positioning of the dummy.

If an automaker uses actual people to validate its suppression system for compliance, FMVSS 208 requires that the system enable the passenger air bag when a female who weighs between 103 and 113 pounds and who is between 55 and 59 inches tall is seated in the front passenger seat, in the position that the standard specifies. FMVSS 208 also specifies the type of clothing that is to be worn for the purposes of compliance testing.

Manufacturers also have the option of confirming that their suppression systems meet the requirements for disabling or turning off the passenger air bag by using either crash test dummies or human beings. FMVSS 208 specifies the child dummies that can be used for compliance purposes, from newborn to 6 year old and specifies the weight and height ranges for the categories of actual children that can be used instead of the test dummies. FMVSS 208 also specifies the positioning of the test subjects including positioning in a number of different infant and child restraints that are called out by the standard.

An occupant's body proportions can affect the Passenger Sensing System's ON or OFF decision. For example, a thin person with long legs would likely apply less pressure on the system than a shorter person who weighs the same but carries more of their weight in their torso. This is because of the relative amount of weight that would be directed through the occupants' legs and not measured.

An occupant's seating posture can also affect the system's ON or OFF decision. If an occupant shifts more of their weight off of the seat, the system will assess that occupant as weighing less than another occupant of the same weight and height who sits upright and centered on the seat. Sitting upright and centered on the seat cushion allows the greatest amount of the occupant's weight, mass and body surface to be centered over the system's sensors. This creates the greatest opportunity for the Passenger Sensing System to recognize an adult-sized occupant.


Service Consultant: Alright Mr. Buchanan, let's take a look at the car.

Man: Oh honey, would you move the seat massager away, please. I forgot.

Service Consultant: Actually Mr. Buchanan, I'm glad you forgot because that just may be a problem.

Wife: But I always use that on my seat, I never ride without it.

Service Consultant: Well, the Passenger Sensing System is very sensitive and works on a very strict set of parameters and thresholds. Something like a seat massager could affect how the system operates.

Man: Wow, I'm glad you told us that.

After market additions like aftermarket seat heaters, cushions, beaded massage appliances and even simple seat covers can affect how the system operates. Customers may want to consider not using any of these things if their vehicles have the Passenger Sensing System. And after market equipment is one of the first things to ask about when investigating a customer concern. Stowing things under the passenger seat or between the passenger seat cushion and seatback may also interfere with the operation of some of the Passenger Sensing System technology. What should you do if there is no aftermarket equipment on the passenger seat and the passenger air bag is off when an adult-sized occupant is in the seat?

Service Consultant: Alright, now according to the vehicle's Owner's Manual, 'If a person of adult-size is sitting in the right front passenger's seat and the off indicator is lit, it could be because that person is not sitting properly in the seat.'

Wife: Well look, the air bag light says it's OFF.

Service Consultant: Well then let's try this again. I'm going to put the ignition to off like it says in the Owner's Manual and put the seat all the way to its upright position. Be sure to sit straight up and in the center of the seat with your legs comfortably in front of you looking forward.

Wife: I can do that.

Service Consultant: Mr. Buchanan, if you would close the door and step back. I'm going to start the car and we'll see what happens with the Passenger Sensing System status light.

Man: I'm just going to hop in the back, I've never been back there before.

Service Consultant: Be my guest. All set?

Man: Ready.

Service Consultant: Alright, great.

Man: Hey, look at that, the passenger air bag is on.

Service Consultant: Now Mrs. Buchanan I'm going to ask you to stay in that position for about two minutes, to allow the system time to adjust its threshold to help stabilize the decision to enable the air bag.

Wife: I'm so glad that we talked to you!

Service Consultant: You should remember one thing. Air bags are only supplemental restraints, they're meant to work with safety belts. So everyone in the vehicle has to be properly restrained, even if there is an air bag.

As a service consultant it's important to know what to ask, what to look for and how these new systems are supposed to work. Never assume there's something wrong with the system because the status indicator shows an ?Air bag OFF' light when a small adult is in the passenger seat. Evaluate the customer's seating posture, like the Service Consultant did with Mrs. Buchanan.

Identify other factors that could affect the Passenger Sensing System, like aftermarket equipment. Then if the air bag is still off understand that some very small adults might apply too little weight or pressure to the passenger seat for the Passenger Sensing System to enable the air bag. Simply put, the passenger seat should be free from obstruction of any kind, whether under, over or in between, including aftermarket products. To maximize the system's ability to recognize smaller, adult-sized occupants, they should sit centered and upright on the seat. The seatback should be fully upright and their feet comfortably extended in front of them. They should maintain that position for about two minutes.

Children should be properly restrained in the back seat. If a child must ride in the front passenger seat, they must be properly restrained in a child safety seat or booster seat. If they are large enough, they must be in a safety belt. 'A child in a rear-facing child restraint can be seriously injured or killed if the right front passenger's air bag inflates. This is because the back of the rear-facing child restraint would be very close to the inflating air bag. Even though the passenger sensing system is designed to turn off the passenger's frontal air bag if the system detects a rear-facing child restraint, no system is fail-safe and no one can guarantee that an air bag will not deploy under some unusual circumstance, even though it is turned off. We recommend that rear-facing child restraints be secured in the rear seat, even if the air bag is off.

If a forward-facing child restraint needs to be secured in the right front seat, always move the front passenger seat as far back as it will go. It's better to secure the child restraint in the rear seat.' Remind customers that air bags are supplemental systems. They are not the primary or only occupant restraint. Everyone who has outgrown child restraints should wear a safety belt properly, whether or not there is an air bag for that person. It also is helpful to refer customers to the owner's manual for important information about the proper restraint of adults and children.