Airbags deployed

What’s your insurance like? File a claim? It’s a 3rd gen? What year, miles, condition?

 

I've heard insurance companies will "total" a car if the air bags are deployed. Even without collision insurance, that's maybe food for thought? Talk to a body shop, get some quotes. Even if you don't follow through with them, gives you some idea.

Can you post pics of the damage from the impact with pole? Front end? Hopefully you can appreciate levity right now; it better not look like this...

 

Usually if the airbags deploy then the srs control module is done- toast- put a fork in it. Almost all manufacturers stipulate replacing the module, all deployed pyros, and the clockspring ( if the driver's airbag was involved).

For testing purposes, IDK if you could unplug the srs module then clear other codes to see if the car will ready up and go into gear. Anything more will (likely) require lots of replacement parts (which is why a "minor" collision can result in a car be declared a total loss).

Posted via the PriusChat mobile app.

 

Your car barely shows any damage in front. A couple of months ago my Gen 3 had a rear-end accident. The front bumper cover was torn, driver front side lights damaged, even the inverter pushed backward by 1/4". But the airbags were not deployed.

Just wonder how the car decides the impact to set off the airbags.

 

Yeah looks very minor. The hood seems pushed up a bit though.

At least get a quote or two, for professional repair.

 

Prius vehicles have 3 generations of impact sensors.

The first generation impact sensor is a "simple" metal ball held by a magnet at one end (e.g. towards the center of the vehicle), and electrical contacts at the other end. So, when an impact happens, the kinetic energy of the metal ball overcomes the force of the magnet, goes forward, and connects the electrical contacts at the other end of the sensor.
The nice thing about those types of designs is that they are simple, reliable, very resistant to any electrical noise/spikes (like may happen if a battery shorts before/in a crash), etc.
However, they clearly are very directional, and therefore, are not that good at detecting an angular impact.

The 3rd, latest generation, impact sensor uses a mutli-axis force sensor, and can it be located at different places on the car/vehicle.



Here's a good overview, just ignore the math stuff .
https://www.experts.com/content/articles/kenneth-solomon-airbag-paper.pdf
Some quick excerpts that cover most of the theory:
======
CRASH SENSOR HISTORY
Early air bag deployment systems in older vehicles utilized mechanical sensors for crash
detection, which were phased out of the US market around 1994. Early mechanical sensors,
such as the “rolamite” by Sandia National Laboratories, relied on a metallic sphere that was
stabilized at a standby position by a spring or a magnet.

When the sensor was subjected to a force beyond a designed threshold, the spring or magnet
could no longer keep the metallic mass in place. The mass moved and made contact with an
electrode, sending an electrical signal to the air bag control module, which then sent a signal to
the air bag control module. Systems with mechanical sensors were generally inaccurate at
interpreting minor collisions. Movement within mechanical sensors can be underrepresented
with frontal collisions, and the acceleration the sensor experiences are sometimes slightly
delayed. As an improvement, modern air bag deployment now relies on microelectromechanical
system (MEMS) components.
(Note: Micro-electromechanical systems (MEMS) is a process technology used to create tiny integrated devices or systems that combine mechanical and electrical components.)

NEW CRASH SENSING SYSTEMS
New MEMS crash sensors measure acceleration with an accelerometer that sends a continuous
stream of data to the air bag control module. Accelerometers are typically piezoelectric or
variable capacitance sensors. The most common MEMS accelerometer in use today is the
ADXL-50 by Analog Devices.

As an anchored mass moves relative to the sensor’s body due to acceleration, a plate attached to
the anchored mass moves closer to a stationary plate. The change in distance between the plates
affects the capacitance of the sensor, or the ability to hold an electrical charge. This change in
capacitance is easily measured and is then converted to a change in voltage. The voltage change
is directly correlated to force due to acceleration, and the readings are interpreted as acceleration
by the air bag control module. Using an algorithm, the control module can determine if air bag
deployment is necessary based on the pattern of the acceleration pulses over time.


THE DECISION PROCESS
The air bag control module (ACM) receives a continuous signal from each MEMS sensor and
records the data for a fixed period after a specific event. With a central processing unit (CPU), it
performs algorithmic computations and controls the “fire” or “no-fire” command for air bag
deployment. The triggering algorithms determine crash severity by evaluating one or more of
the kinematic variables (derivatives/integrals of acceleration) shown in Table 1. Examples of
algorithm decision flow charts are shown in the following Figures 3, 4, and 5.
...
Two vehicles of similar weight may have very different stiffness values, as seen when comparing the 2010 Ford Fusion
to a 2010 Toyota Prius. Both vehicles have approximately the same vehicle weight, yet the
front-end stiffness of the Toyota Prius is substantially greater than the Ford Fusion. Since both
the amount of displacement and the duration of impact for a Ford Fusion are greater, an air bag
would need to deploy in the Ford Fusion within a range of deceleration values lower than those
required for the Toyota Prius.
======



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Well it may not seem much but the damage is there. The hood is clearly pushed up which require a body work. Not sure if the fenders are out of alignment as well.
Could you tell us the contact point? I can't see which part of the bumper came in contact with the pole.

 

Five friggin miles an hour? That’s all it takes? Are you sure she’s being honest?

 

Good to know it is MEMS. Thanks.

 

Argh, I just noticed for the first time that whoever made the PDF copy of Gen 3's repair manual that's been circulating online used the airbag section from Gen 2. (Pages 6775 through 6956 of the PDF, and sure enough, that's a drawing of a Gen 2 on page 6775.) Well, you get what you pay for,

Yuck. So somebody will have to go to TIS or the library (more info) to see the right repair info for Gen 3 airbags.

But the Gen 3 wiring diagram does show a similar design, where the "center airbag sensor"/ECU is on the center cabin floor roughly below the heater, and there are also front left and front right deceleration sensors mounted out at the front corners of the car.



To trigger the front airbags, there needs to be agreement by the "safing" sensor inside the center unit that the car is decelerating above some minimal rate, at the same time as one of the front decel sensors detects a rate high enough to call for the airbags. The (wrong, Gen 2, argh) manual also says there's a decel sensor inside the center unit that can trigger the airbags without a front-sensor signal, if the deceleration at the center sensor is strong enough.

I am wondering if there was some pre-existing weakness in the body structure where the front sensors mount (rust, or frame damage from an earlier collision, etc.), or one of the front sensors was somehow not mounted securely.

It's trying to measure the force of the collision by how fast the nose of the car is decelerating, but of course it really only sees how fast the sensor decelerates. If the sensor was somehow insecurely mounted, or mounted on some weakened structural metal, it could have been knocked back more than you'd normally expect for a 5 mph collision, enough to trigger the airbags.

Don't forget to also replace the front seatbelt retractors, which probably had their pretensioners ignited.

 

That's good to hear!
Congratulations on the repair!