Another warning indicator you see on a dashboard is the dreaded air bag light. These airbag problems can be much more complicated to repair than let's say a check engine light issue.
The airbag specialized scan tool pictured to the right is a reasonably priced piece of equipment at around two hundred dollars. They do make other SIR (Supplemental Inflatable Restraint) code readers in this price range, but the problem is none of them cover all vehicles. For this reason, always verify your car is on the application list before jumping in.
On some cars, when the module senses a malfunction, the light will continually flash codes. On others the light might be on steady until you enter a diagnostic mode. To be honest, it's a mess, because it is not standardized like OBD II. I recently diagnosed and repaired a Toyota Corolla with a steady flashing light with no codes. I'll add this story at the bottom if you're interested.
For domestic vehicles, they have the OTC 3111 Pro. This thing can read and erase OBD II codes plus display and erase ABS and Airbag (SRS) trouble codes.
The on-board code library feature provides definitions on screen of pulled codes. A big point to make is the ABS and Airbag functions are limited and will not work on all model cars and trucks. OTC states it works on most domestic vehicles 1996-Present.
Two things to make clear. You can use the the scanner to read and clear codes. However, it's recommended to leave the servicing of this important safety system to professional technicians. Second, is the coverage is spotty, but I show the tool, because if it works on your car the unit is handy.
The next lucky group of people that would have access to a cheap scan tool that can read airbag codes is the owners of German cars of the 90's. Specifically, the Volkswagen and Audi models.
If you own a modern Volkswagen or Audi you can read many codes including Engine, Transmission, Airbag and ABS. They designed the Roadi scanner to read VAG system trouble codes on 4 systems. The code definitions display right on screen. It works with Volkswagen and Audi's from 1990 or newer.
They deployed the SRS (Supplemental Restraint Systems) on German cars back in the 80s. The problem of the illuminated air bag light is becoming more common on these aging cars and trucks. It's for this reason I decided to write a quick article about what I find most often causing the light to flash or stay on.
Keep in mind that these are complicated systems and many things can cause the warning light to flash, stay on or not come on at all. Communicating with the control module is often required. Some manufacturers require a scan tool for diagnosis.
Other manufacturers flash the code from the dashboard warning light. You'll have to get an auto service guide for your specific model to determine how to read the flash codes, because procedures will vary between companies.
They designed the dashboard mounted indicator to let the driver know the system is ready to do its job. Of course this would be to deploy the quick inflating bag during a hard collision. On most vehicles the lamp is operated through the main control module.
The light should illuminate when you turn the key on for a bulb check. On some models the light will flash briefly while the system runs a complete diagnostic. But when the engine is running the light should go out.
If the module detects a malfunction during the diagnostic test the airbag light may stay on continuously or even flash. This could mean a problem that would prevent the airbag from deploying in the case of an accident. For this reason perform diagnosis as soon as possible.
One of the components getting a constant workout in any SRS system is a part mechanics call the clock spring. The airbag clock spring allows for constant electrical contact to the steering wheel mounted module and related components at all times.
They locate the clock spring between the steering wheel and the steering column. It contains a conductive flat ribbon that maintains this needed contact during steering wheel rotation. This important component feeds power from the vehicle's battery up to the module. Thus, it's responsible for providing the needed energy to deploy the bag.
If electrical contact is disrupted between the module and the airbag clock spring, a code will be set and the warning light flashes to indicate there's a problem.
Since this is one of the only components that constantly moves in the SRS system it's also one of the most common failures.
Replacement of the SRS clock-spring requires the removal of the airbag assembly and the steering wheel. This operation could require some special tools to complete the repairs. Accidental deployment when removing the air bag isn't common, but is possible. For these reasons it's best to have it replaced by a qualified car mechanic.
Diagnosis of many air bag light faults is impossible without some special tools. On many GM products you need a bag release tool to remove the deployment module. On Ford vehicles from the late eighties well into the nineties a special tool called a simulator is used to aid in diagnostics.
Because the circuit remains open when you unplug the module many testing procedures cannot be performed. The simulator provides the correct resistance and specifications as a good part would. This allows the diagnosis to safely continue.
The Ford special simulator tools are essential for body repair shops but can also be helpful for mechanics trying to diagnose air bag lights. Some diagnostic tree charts in the Ford service manual require the use of one of these air bag simulators because they will simulate a complete circuit for diagnostic purposes.
Bookmark this air bag light page or share with a friend.
I had a 02 Corolla come in with a flashing warning light. As I sat there trying to count the flashes I realized that it wasn't indicating a stored code, but rather it was stuck in diagnostics. There was no pause in the flashes to indicate a 2 digit code.
When you turn on the key it goes into an automatic self test mode. Basically the module sends out a reference signal to all of the sensors and actuators and waits for the return voltage. On this Toyota corolla it never got the return signal.
The reason was the wiring harness had high resistance. A friend of mine that works at a dealer gave me the heads up on this so I can't take credit for it. If you have a Lexus or Toyota with problems in this area there is a quick learning guide available in many different formats including Kindle, Android and MP3. Often you can't use normal diagnostic procedures when dealing with these pyrotechnic safety systems. Therefore seeking out specialized information is recommended.
The homepage is still the best place to go for a run down of the massive amount of information covered here. You can find many answers to car questions on the auto-facts.org Homepage.
More articles about dashboard warning lights and common problems that cause them are grouped on my auto scan tool page. This next link will take you there from this page about the air bag light.