The Stanley Subaru Scoop

What is an Occupant Detection System (ODS)? How Does an ODS Work?

Stanley Subaru answers these questions with this week's Technical Schmecnical Lesson.

Federal Motor Vehicle Safety Standards require the use of an Occupant Detection System (ODS). This system is designed to determine if a person is seated in the front passenger seat*, and, more importantly, if the person is of adequate size to be protected in the event of the deployment of the front passenger seat airbag (SRS) in a moderate to severe frontal collision.

Most Occupant Detection Systems measure the weight of the front seat passenger, to determine if the front passenger seat airbag should deploy.

All 2012 and 2013 Impreza and 2013 BRZ models use a new type of Occupant Detection System called Electrostatic Capacitance Sensor ODS. This system does not use weight to determine whether to turn the Occupant Detection System ON and OFF. 

The Electrostatic Capacitance represents a material's capability of storing an electrical charge.  Have you ever been shocked when walking across a carpeted floor and touching a doorknob? This demonstrates your ability to store an electrical charge in your body.

When anyone is seated or when anything is placed on the front passenger seat, there is a change to that capacitance value.  This change in capacitance value is what the Electrostatic Capacitance Sensor ODS uses to determine whether the front passenger seat airbag (SRS) will be ON or OFF.

Everything that is placed on the seat will affect a change in capacitance value.  The system can determine whether to change the OFF status of an airbag to ON depending on what is on the passenger seat which in turn causes a change in capacitance value. 

Some examples:

>A proper sized passenger will change the OFF status of an airbag to ON.

>Platic, metals and other substances, even if at a heavy weight, will not change the OFF status of an airbag.

>A false electrical charge, for example, those caused by laptops that are processing data, cellphones that are on, or even an electric device connected to a car charger can cause the airbag status to switch ON.

>When water or anything with high moisture content is spilled on the front passenger seat cushion, the airbag is designed to remain OFF until the seat cushion is dry.  This will also be the case if the passenger has moisture on their clothing, such as rain-soaked pants or rain gear.  In each of these situations, the airbag status may remain OFF even if a passenger is seated.

The Electrostatic Capacitance Sensor ODS on 2012 and 2013 Impreza and 2013 BRZ models uses a low level electrical charge to determine what is on the front passenger seat.  This low level charge will NOT result in an electrical shock.

Passengers are advised NOT to sit in the front passenger seat if the seat cushion is wet or if their clothing is wet.  The best way to ensure proper operation is to keep everything off the front seat except a passenger. 

Remember, anything not belted in can be a projectile in the event of a crash and could increase injuries.

For more detailed information, please read and understand the Owner's Manual.

*Passengers seated in the front of the vehicle must meet all State and Federal Regulations according to the Federal Motor Vehicle Safety Standard 208. Never install a child seat or booster seat in the front of the vehicle. See Owner Manual for more details.

Categories: Technical Schmecnical


So what is one supposed to do when you have a full car and you go swimming, it rains, you are sweaty...etc? Just tell the front passenger, "sorry if we are in an accident the airbag won't go off."??? Horrible design by Subaru.
Post Follow Up
Jeanne Dennison
You raise a good point Kevin. I agree that sometimes our lifestyles play out differently than automotive engineers intend. When Subaru was researching these systems, they believed that the safety benefits of this new feature outweighed the negatives. Perhaps there were more safety concerns with the older technology that warranted this significant change. As always, Subaru is constantly evolving and changing and as improved technology is made available, we'll see improvements on existing features. Subaru takes driver concerns seriously, as most of the automotive safety and convenience features were Subaru-owner's suggestions. As a Forester owner myself, I know the joys of carting people to local swimming holes and this does pose a concern. Perhaps we could include chamois cloths with new Subaru purchases for just those occasions. --Jeanne
Post Follow Up
Claude Mosley
I have a 2012 Legacy that had a frontal hit that set off the air bags. After resetting the controller, replacing air bags and seat belts I still have a problem that the passenger is not recognized. I had a Subaru dealer recalibrate to detection control and was told that I must replace the seat since the dash air bag when off. Does this sound correct?
Post Follow Up
Jeanne Dennison
Claude, I will talk to one of our Subaru Certified Master Technicians and have an answer for you shortly. --Jeanne for Stanley Subaru.
Post Follow Up
Jeanne Dennison
After speaking with our Service Manager, he informed me that it is true the seat will need to be replaced. Thank you for your question.
Post Follow Up
Michael McGeough
Please help! This is a safety issue. My wife has back problems and uses a rubberized seat cushion. The passenger air bag sensor, which is an Electrostatic Capacitance Sensor ODS, does not work with her cushion even with me at 240 lbs! I want to over-ride the air bag sensor so it is ON. The dealership says they can't do anything. I tried a Chamois cloth, (damp and dry), plastic bags, towels, (damp and dry), coils of wires, etc. under the cushion. I cannot find a way to turn on the air bag. It works fine without the cushion but she can't ride for very long that way. Please help! I will twist the wires together if necessary, but I don't have a schematic. I would much prefer an old fashioned pressure sensor. This device does not work.
Jeanne Dennison
We are very sorry for the troubles you and your wife have been having with the Electrostatic Capacitance Sensor ODS. Unfortunately, the sensor requires direct contact in order to activate, and the rubber cushion blocks the sensor. This problem also occurs if the occupant is wearing water-soaked clothing. I'm not aware of any methods to override the system.  It is advised that your wife avoid using the cushion while riding in the passenger seat, since it will not activate the air bag.  Please contact Subaru Customer Service directly to see what they can do about your situation: Customer Service: 1-800-SUBARU3 (1-800-782-2783). Again, we are so very sorry that you are experiencing this safety concern.
Claude Mosley
So why does the seat cushion need to be replaced if a air bag goes off?
Is there a fix without replacing the entire seat cushion?
Spencer Patterson King
Hi, Claude,

There are a couple reasons the cushion might need replaced after an airbag deployment (including the SRS wiring, damage, and others). Without looking at the vehicle, we couldn't say. Your local Subaru dealer should be able to tell you once they've inspected it.
Post a Comment
true true true true true true true true true true true true