If you’re anything like me, you hate warning lights on your dashboard because it’s your car’s way of telling you to get your shit together. One of the more dangerous lights you can have on is the airbag warning light. Here’s how to diagnose and fix it without the risk of near-face explosions.
The work performed is on a 2004 Toyota Camry. Other cars may be different, but this represents a common case of why airbag lights may be illuminated. When working on an airbag system, exercise extreme caution. If you’re not confident in your ability to do the work, consult a professional.
A car’s airbag system is quite simple - it consists of a few sensors, a module that interprets the signal, and an airbag which has an element that allows for rapid deployment by a small charge placed in the bag. Over time, these sensors can wear out and become defunct. Thankfully, your system constantly monitors the state and readiness of these sensors, just in case you decide that your Egg McMuffin is more important than the road.
The two most common sensors to go bad on a modern car are the passenger’s occupancy sensor and the clock spring.
The passenger’s occupancy sensor is a weight-sensitive element that noticed if you have more than a certain amount of weight in the front passenger’s seat. This is made so smarties who put their babies in the front seat don’t have the airbag deploy right into the back of their infant’s head during a crash, but their fat bowling buddies will get a ‘bag to the face should the situation call for it.
With the ability of seats to move forward and back, the sensor’s wiring harness can get stretched and frayed, or worse - completely disconnected from the seat itself over time. The way you know if the sensor is at fault or not, before scanning your airbag system for faults, is to simply look at the “Passenger Airbag Off” light. If there’s no one in the seat, the light should illuminate. If there is someone in the seat, the light should turn off, signifying that the system is armed. The default state of the bag is to arm, so there’s likely no case where someone will sit in the seat and the airbag will not deploy.
If, for some reason, the light never illuminates when no one sits in the seat, the sensor could be at fault. First, check the wiring underneath the seat to see if there’s anything knocked loose, making sure that there aren’t any frayed wires.
If all is well, then you can either have the seat taken apart and have a new pad put in, which can be expensive, or you can simply bypass the occupancy sensor with a universal or plug and play kit, rendering the bag armed when the car is running. This is an optimal solution when you know that you won’t have any child seats or young children in the front of the car in the foreseeable future.
With a plug and play kit, all you do is disconnect the yellow connector underneath the seat and wire in the bypass module for your car. With a universal kit, you’ll have to splice into the wires, which I wouldn’t advise if you’re a novice or don’t have a wiring diagram in front of you. The last thing you want is wires crossed in an airbag system, especially if that determines whether or not the airbag deploys on a passenger.
Moving ahead, the next most common issue with airbag systems is the car’s clock spring. This is the electrical coupling between the steering column and steering wheel. This also allows your horn and wheel-mounted buttons to function. A dead giveaway of a bad clock spring is an airbag light and broken horn, despite all fuses being good. With this fix, the steering wheel has to be removed, but it’s quite a simple process and can be completed with hand tools in under 20 minutes. Also, unless your car is super rare, it never makes sense to buy used clock springs when new ones are available and quite affordable.
Before any airbag work, remove the negative battery cable from the terminal and wait 10-15 minutes for the capacitors to discharge.
Point your wheels straight, with the steering wheel facing straight. Next, locate the screws holding the center section of the wheel in place, including the airbag. This is usually a small hex bolt or Torx bit. On some Nissans, you will need a tamper-proof Torx bit. In my case, it was one T30 torx bolt on either side of the steering wheel. Sometimes these loosen but do not come out. This is normal.
Next, pull the airbag toward you and remove the connectors. You can use a pick and slide the yellow clips out to remove the connector. You can now remove the airbag.
Turn the steering wheel left and right to expose the screws holding the steering column trim in place. Note: some screws can be located on the bottom of the trim. Pry off the bottom of the trim with a plastic spreader tool of a flat head screwdriver.
Engage the steering lock to make sure that the wheel doesn’t move for this next part. Take two pieces of painter’s tape and place it between the steering wheel and the steering column trim. These will be your alignment marks for when you put the steering back to its original position.
Take a breaker bar with the appropriate sized socket and loosen the steering wheel nut a few turns, but do not take it off completely.
Most steering wheels, over time, have created a fairly strong bond with the steering shaft, so it will take a bit of pulling back and forth in a jerking motion to get the wheel free. The column nut should stay on so you don’t punch yourself in the face after tugging on it. Yes, it’s happened to me. Don’t make my mistake. When the wheel is loose, you can remove the nut and the wheel, exposing the clock spring.
Disconnect the harnesses at the bottom or back of the clock spring and remove the old clock spring. There may be bolts holding it on, but in my case, there were only clips.
The new clock spring should have a locking tab so it doesn’t stays centered in the correct orientation while shipping. Install the new clock spring and break this tab off by bending it until it snaps.
Install the steering wheel, lining up the tape marks that you made before removal.
Tighten the steering column nut to the specified torque with a torque wrench - Google is your friend when it comes to torque specs. If you can’t find torque specs, I’d go with as tight as you can make it with your hands and a breaker bar, adding a dab of thread sealant beforehand. You can now install the harnesses and airbag, making sure the bolts are hand-snug and you’re not binding with anything. Reinstall the lower trim piece and reconnect the negative battery terminal and turn on the car.
You should no longer have an airbag light on and your horn will now work. Hooray!
Not all airbag lights are due to these issues, but most are because these components are the ones that take the most abuse and are the most susceptible to failure. If none of these procedures work for you, you can try googling how to perform an airbag system reset, which will reset all warning lights and/or display error codes if they persist.
Some airbag problems require professional diagnostics equipment, so if you think that your car has a fault but doesn’t exhibit the symptoms I’ve discussed, it’s best to consult with a mechanic with the skills and tools necessary.
In any case, I hope that this quick DIY illustrates how easy it is to fix an issue with your car if you’re willing to spend a little time on it. Happy modding!
Tavarish is the founder of APiDA Online and writes and makes videos about buying and selling cool cars on the internet. He owns the world’s cheapest Mercedes S-Class, a graffiti-bombed Lexus, and he’s the only Jalopnik author that has never driven a Miata. He also has a real name that he didn’t feel was journalist-y enough so he used a pen name and this was the best he could do.
You can also follow him on Twitter and Facebook. He won’t mind.