Airbags and sensors, question Options

[MaskedMan]

I was just wondering how the airbag sensors on our Celicas operate. I've read up about different types of sensors, but I'm not sure which kind were used on our cars. Also, if the airbags were to deploy and the vehicle were to be repaired, is it nessecary to replace the airbag ECU as well or will it be alright to reuse the airbag ECU?

One more thing. What is the easiet way to remove the passenger side airbag? Is it required to remove the dash or is it accessable by removing the glove box?

Thank you.

[Hanyo]

from what i heard and seen and tried...

YOu need to replace everything, including the dash. The reason is because when the passanger side air bag explodes it rips part of the dash. So it is required to change it also.


The two air bag sensors, air bag ecu, air bags need to be replaced...

[lubu]

I dont think you need to replace the airbag ECU, the ECU is responsible for the monitoring the sensors and if they tripped the ECU then provides power to the airbag for ignition. There for it doesnt receive any damage after the impact.

[MaskedMan]

from what i heard and seen and tried...

YOu need to replace everything, including the dash. The reason is because when the passanger side air bag explodes it rips part of the dash. So it is required to change it also.


The two air bag sensors, air bag ecu, air bags need to be replaced...

Well it looks like the dash isn't ripped at all. Just the little rectangle cut out popped up and it might have cracked, but it's still in one piece.

I dont think you need to replace the airbag ECU, the ECU is responsible for the monitoring the sensors and if they tripped the ECU then provides power to the airbag for ignition. There for it doesnt receive any damage after the impact.

Well in my head I was thinking this. That maybe once the airbag ECU sends the signal to the airbags to deploy, it locks up and isn't able to be reset. But I'm not sure how exactly it works, or why we even need one. If the sensors alone can complete a circuit, and the only thing airbags need is power to deploy, then what exactly is the ECU's purpose? I suppose it's a safety device of some sort so that the airbags don't go off for no reason but, I'm very interested in how our system works. I guess I should have paid more attention in class that day, but I was too excited because I was waiting to detonate an airbag that day. It was my first time seeing an airbag deploy, so I was excited haha.

Thanks for your help Hanyo and lubu. If you have any more information that you think can help me with my airbag knowledge, then please share .

[lubu]

I just did some research found that in the event of a crash the ECU writes a crash code into one of the ICs, and thus the checkligh will always stays on.

The good thing is you can reset the ECU, I found these guys, looks like it's cheaper than buying one from toyota.

Here's a direct quote from Wiki:

The design is conceptually simple; a central "Airbag control unit"[12] (ACU) (a specific type of ECU) monitors a number of related sensors within the vehicle, including accelerometers, impact sensors, roadwheel speed sensors, gyroscopes, brake pressure sensors, and seat occupancy sensors. When the requisite 'threshold' has been reached or exceeded, the airbag control unit will trigger the ignition of a gas generator propellant to inflate a nylon fabric bag extremely rapidly. The inflated airbag reduces the deceleration experienced by the passenger during the crash. The bag has small vent holes, to allow the propellant gas to be slowly expelled, in a controlled manner from the airbag, as the force of the occupant pushes against it.

edit:typos

This post has been edited by lubu: Jun 4, 2008 - 12:05 PM

[brk34]

I found a link similar to the previous one.

http://www.r5tool.com/srstool.htm

[hurley97]

IIRC the airbag ECU does control all the sensors and determine when to deploy the airbags as well as being used as a sensor itself in essence.

When the airbag ECU will deploy the airbags if it senses the deceleration of one sensor is higher than that of the others or the deceleration of all of them are above a predetermined limit.

There was a retrofit available from Toyota (long ago when they were still under some sort of factory warranty) that mounted a switch in the glove compartment to turn the drivers and passengers airbags on or off. Of course it's unavailable now and I think even then there was a big process to get the kit that included an submitting an application in to have it DOT approved and the kit was sent straight to the dealership after a few months, or something crazy like that.

[MaskedMan]

Thanks for the help all of you . I will go ahead and replace the Airbag ECU while I'm at it. I would hate for my airbags to malfunction just because I wanted to cheap out and not replace the ECU as well.

One more question though. What is the proper way to test an Airbag sensor? Is there a way? Because I am purchasing airbag sensors off a member here, and I want to be sure that they are still operational after they are shipped (you know how rough shipping can be). Oh and, the links had a lot of good information, but does anybody know how many airbag sensors our Celicas have? I just need to know so that I can replace each one that may be damaged. The Celica was involved in a front end collision on the passenger side of the car, causing the airbags to deploy. I see there is an airbag sensor right there next to the radiator. That one I am going to replace, along with the one of the driver side as well, just to be safe. Are there any other sensors that I'm missing and/or should replace?

[lubu]

One more question though. What is the proper way to test an Airbag sensor? .....

LOL....crash it!

I think you can test it by taking out the signal wires that goes to the ECU or airbag and put a voltmeter across those wires. Now take the sensor(s) in ur hand and quickly swing ur hand to the wall, the sudden stop should act as an impact and if you see the voltmeter registers a current/voltage then the sensor is working.

But I dont know if you can resuse them once you try them out.

Not recommended though.

[MaskedMan]

One more question though. What is the proper way to test an Airbag sensor? .....

LOL....crash it!

I think you can test it by taking out the signal wires that goes to the ECU or airbag and put a voltmeter across those wires. Now take the sensor(s) in ur hand and quickly swing ur hand to the wall, the sudden stop should act as an impact and if you see the voltmeter registers a current/voltage then the sensor is working.

But I dont know if you can resuse them once you try them out.

Not recommended though.

I always thought the sensors were one time use only. The more I think about it, the more complicated and in depth my questions become haha. Also, swinging my hand into the wall doesn't seem like a valid test . Actually I get what you mean, it could possibly show that the sensors will operate if that were to happen, but I'm almost positive I would have to buy new sensors after that test haha.

[hurley97]

I was just looking in the BGB and it seems like the only real way to test the sensors is to install them in the car and check if there are any airbag DTC's

maybe you could do some of the tests for when it says the sensor is bad but those seem to also involve testing while connected to the harness.

it does list Replacement Requirements for the center airbag assembly and sensors as the following:
- If the SRS has been deployed in a collision. (Replace both left and right airbag sensor and center airbag sensor)
- If the airbag sensor has been found to be faulty in troubleshooting.
- If the front and/or center airbag sensor has been dropped.

Also under removal and installation instructions there is a notice reading:
- Never use SRS parts from another vehicle. When replacing parts replace with new parts.
- Never reuse the sensor involved in a collision if the SRS has deployed.
- Never repair a sensor in order to reuse it.

also the front airbag sensor have to be torqued to 22 ft/lbs