By law, all cars are required to have three-point seat belts, which must be worn by the driver and all passengers when the vehicle is moving.
In addition to this legal requirement, many cars nowadays come equipped with a supplement restraint system (SRS) to provide added protection for the occupants of the car. This safety system has made a dramatic difference in protecting occupants.
So, what does SRS mean in a car? That’s what we want to clarify and discuss in this post. Plus, I’ll tell you how to diagnose and fix SRS warning light.
What Does SRS Mean in a Car?
Today’s cars are safer than they have ever been. They have advanced design and construction that provide reliable protection in the event of an accident.
Your airbags can be a real lifesaver. They are a part of a very unique protection system of computers and sensors in your car, referred to as the supplemental restraint system (SRS).
The sensors are purposefully located in your car. They detect different parameters, including occupied seats, the weight of each occupant, and the direction and speed of an impact in a collision.
The supplemental restraint system module does a good job of determining the severity of a collision with the help of the impact sensors. The SRS module will only deploy the pre-tensioners and airbags if the detected collision is of sufficient force. The SRS may deploy the seat belt pre-tensioners if the impact force isn’t enough to warrant airbag deployment.
The two most common types of impact sensors are capacitive and piezoelectric. One is made up of a piezoelectric element that will distort in the event of a collision. It produces an analog voltage depending on the severity of deceleration forces. The piezoelectric element can also detect the direction of impact force.
The capacitive sensors, on the other hand, have a design similar to a capacitor. Some of the capacitor plates are mounted to a moveable unit while others are fixed.
What Is the Meaning of SRS Warning Light?
When you initially switch on your ignition, the SRS warning light will illuminate on the dashboard for about seven seconds to indicate that the system is functional and that the control unit is conducting a self-test of the system.
The time the light illuminates may differ from one car to another. The amount of time the SRS warning light stays on indicates the length of the system check.
If your SRS system is working just fine, the light will disappear from the dashboard. On some cars, the warning light will flash to suggest a fault code, which may need to be triggered by a diagnostic tool.
Some cars, on the other hand, have an SRS off switch. This is an important feature when you have kids seating on seats that are protected by airbags.
What Causes the SRS Warning Light?
These are some of the common reasons your SRS warning light doesn’t disappear from the dashboard.
Defective Passenger Seat Occupancy Sensor
The passenger side of every modern car is equipped with an SRS system. There is a sensor that detects the weight of the passenger. This allows the SRS system to adjust the deployment strategy of the airbag during a collision event. If that sensor is bad or faulty, the airbag will be inactive and the warning light will display continuously on the dash.
When you check for codes, you are likely to get an occupant classification system calibration fault. You can deal with the problem by replacing the sensor. After replacing the sensor, the system should be okay and be able to detect the weight of the passenger.
Faulty Seat Belt Sensor
This sensor detects whether the occupant’s seat belt is engaged and locked in the housing unit. This allows the SRS system to determine the ideal airbag deployment strategy.
The sensor is usually integrated into the seat belt buckle and it is magnetically operated. When the buckle is unlatched, the circuit is normally open. But when the buckle is latched, the circuit will be closed. If a foreign object gets into the buckle, it will prevent it from latching.
This will cause the SRS warning light to stay on. All you’ve got to do is remove any foreign objects from the buckle to complete the circuit.
Corrosion in the Car
Water leakages inside your car could cause serious damage to your SRS system components. Corroded parts could cause the warning light to stay on. It may be challenging to directly pinpoint the components that have been corroded. The SRS system has to be thoroughly checked by a mechanic and all the corroded components replaced.
Bad Clock Spring
The critical nature of the airbag in an accident requires it to be electrically connected to the SRS system at all times. This way it can be deployed when sufficient impact force is detected.
Because the driver’s airbag is mounted in the steering wheel, a clock spring is used to maintain the electrical connection between the airbag and the computer. A clock spring is a rotary electrical connector that is located between the steering column and the steering wheel. It uncoils and coils as the steering wheel is turned to allow constant electrical contact.
If the clock spring is bad and there is no electrical connection, the SRS warning light will display on the dashboard.
The clock spring is not repairable if the ribbon harness fails. Replacing the clock spring is no easy job and there is the risk of accidental deployment of the airbag. So, it is recommended to hire the services of a mechanic.
Faulty SRS Computer or Dead Backup Battery
The SRS computer controls the deployment of airbags and stores crash data. The most common sign of a faulty SRS computer is the warning light on the dashboard. A low backup battery is another reason your SRS computer may malfunction.
How to Diagnose and Fix SRS Warning Light
During an SRS system check, the ECU will record a fault code that applies to a specific fault from a list of codes stored in the ECU memory.
You can check the diagnostic trouble codes by connecting a diagnostic test equipment to the OBD II port. The test equipment will help you find out what causes the SRS warning light.
Here are the key steps you need to follow:
Step 1: Watch the Warning Light and Decipher the Code
When you start your car and the airbag light stays on or flashes, this means there is a problem with your SRS system.
The flashes are actually giving you a code. If the warning light, for example, flashes four times, pauses, and then flashes six times, this is code number 46. After you read the code, the light will flash about five times, giving you five chances to read the codes. Then it will stay on to let you know that there is a problem.
Code number 46 means that the driver-side seat belt pre-tensioner circuit is broken. This usually happens when you move your seat or stuff things underneath the seat. You can check the connectors for corrosion or breakage. But we recommend taking the car to a mechanic if the process is too complicated for you.
Step 2: Connect a Diagnostic Test Equipment
The warning light may not flash on some cars. So, you can’t decipher the code by watching the light flashing. If this is the case with your car, you will need the diagnostic test equipment to read the fault code(s). You need to find the OBD II port. One of the places you can find it is under the steering wheel.
Turn the engine off and start the ignition only. Then start the diagnostic tool and select the make of your car.
Alternatively, you can click on the auto-detect feature for the tool to automatically scan for the VIN (vehicle identification number) number. When the VIN is detected, the tool will automatically tell you the make of your car.
Select the control unit and then look for the airbag symbol, RCM, or SRS. You will be redirected to the SRS system, where you can see ECU information, read codes, and erase codes. Then click on the read codes and wait for the tool to establish communication.
The fault codes that are making the SRS warning light stay on will be displayed on the screen. If the fault code indicates a bad sensor, then it has to be replaced for the system to go back to normal.
After replacing the sensor, you can check the live data to see if the system is back to normal. You can have someone seat on the passenger side to activate the SRS system and fix the warning light.
What does SRS mean in a car? At this point, you know that the SRS system is a very important part of your car that helps protect you and your passengers during a collision. But sometimes the system may face some problems and the SRS warning light will stay on. You can easily use a diagnostic test tool to check the DTCs and then fix the problem. But dealing with the airbag system could be dangerous. If you think you can’t do it yourself, then we recommend taking the car to a mechanic.