The airbag module gets the credit, but it only knows what the impact sensors tell it. Here is what those sensors do, where they hide in the car, and how to match one to your vehicle.
An impact sensor is a small accelerometer in a sealed housing, usually no bigger than a matchbox, bolted directly to the structure of the car and wired back to the airbag control module. It has one job. It measures how hard and how fast the metal it is bolted to gets slowed down or shoved sideways, and it reports that reading to the module hundreds of times every second.
The module makes the actual deployment decision, and we walk through that in our explainer on what an SRS airbag module is. The sensors are what give it something to decide with. A module mounted low in the center of the car feels a front-end hit late and softly, because the energy has to travel through the whole front structure before it gets there. A sensor clamped to the radiator core support or the frame rail feels the same hit right away. Those few milliseconds of warning are what let the system fire a bag before the occupant has moved forward in the seat.
Side impacts have almost no crush distance to work with. A door skin sits a few inches from a hip. That is why manufacturers put satellite sensors right where the hit lands, inside the door shell or at the base of the B-pillar, and why some vehicles use a pressure-type sensor that reads the pressure spike in the sealed door cavity when the skin caves in. Most cars built since the mid 2000s carry four to eight sensors, each on its own circuit, and the module tests every circuit when you turn the key.
Front sensors sit out in the crush zone: on the radiator core support, on the upper tie bar behind the bumper cover, or on the frame rails just behind the bumper beam, typically one per side. Once the bumper cover is off they are easy to spot, the only thing up there with a short pigtail and a bright yellow restraint connector.
Side sensors take more work to reach. Door-mounted units bolt to the inner door shell behind the water shield, so the door panel has to come off. Pillar-mounted units sit behind the B-pillar or C-pillar trim, and some hide under the sill plate.
Every one of them carries the OEM part number, either on a printed label or laser-etched into the case, along with the supplier name and a date stamp. Bosch, Denso, Continental, Autoliv, and ZF build most of them for the major brands. Write down the full number including the suffix. On restraint hardware a suffix change usually marks a real electrical revision, not a packaging update. Check handedness while you are down there. Some makes use mirror-image left and right sensors with separate part numbers. Others use one identical sensor on both sides and let the bracket do the handing. The label on your old part settles it.
Start with the code. Pull the restraint-system trouble code with a scan tool that can actually read the SRS, then look it up on our airbag code lookup. A code that names a specific sensor position, a right front impact sensor performance fault for example, points at that sensor, its connector, or its wiring. A code that names a deployment event points at stored crash data sitting in the module, and that is what an airbag module reset clears.
Impact sensors have nothing to reset. There is no crash memory inside them and no software to reflash. They pass their self-test or they do not. If yours fails it gets replaced, and the module still has to have the fault cleared before the light goes out.
Two other things keep the light on after front-end body work, and both get blamed on the sensor. One is a connector that came apart during disassembly and never latched all the way back down. The other is a sensor reinstalled on a bent bracket or left loose. A sensor reads whatever it is bolted to, and it cannot read correctly unless it sits flat against solid structure.
One more thing before you order. Manufacturers treat crash sensors as inspect-and-replace items after a deployment. GM's post-collision procedure calls for replacing sensors in the area of the accident damage, and other makers use similar language. If your airbags went off and the front structure was crushed, plan on new sensors in that zone whether they set a code or not.
Every part we list is photographed with the label and connector visible. What to check before you commit:
Platform sharing fools people constantly. The Nissan Armada and the Infiniti QX56 and QX80 share a front impact sensor family across three badges, so parts that look identical really are identical, right up until a mid-generation revision splits them. Assuming that sharing holds for your build year is where people get burned.
Trim changes the sensor count. A base sedan without side curtain airbags does not carry the same satellite sensors as the same car with curtains, and on some vehicles the harness does not even have the circuit. Coupes, sedans, and wagons on one platform get different side sensors because the pillar geometry is different. Convertibles are their own category, since they add rollover sensing and rarely share a sensor set with the hardtop.
Impact sensors are inert electronics. No propellant, no inflator, nothing that needs special handling. They ship ground to the lower 48 states like any other small part. We pack the pigtail and connector so nothing gets crushed on the way.
Installation is within reach of a careful DIYer on most vehicles, and it is genuinely dangerous if you rush it. Disconnect the negative battery terminal and give the system at least ten minutes to bleed off its backup power before you touch a yellow connector. Never probe a restraint connector with a meter unless the factory procedure tells you to. Torque the sensor against clean, flat, undamaged structure. The module will still be holding the old fault afterward, so you or your shop needs a scan tool that talks to the restraint system to clear it. If the front of the car took a real hit, let a shop handle the sensors and the post-repair scan together.
These are restraint components, so read our returns policy before you order. Current inventory is listed in the parts store. If your sensor is not there, call 501-988-0611 with your year, make, model, VIN, and the number off the old part, and we will check for you.
No. There is no stored crash data inside a crash sensor and no software in it to rewrite. It passes its self-test or it fails. Resets apply to the airbag control module, which is the part that stores the crash record.
Manufacturers treat them as inspect-and-replace items. GM's published post-collision procedure calls for replacing sensors in the area of the accident damage, and other makes use similar language. A sensor sitting in a crushed corner should be replaced whether it set a code or not, even if it looks fine.
Only if the OEM part number matches exactly, suffix included. Trim level, body style, and mid-year supplier changes all split part numbers on restraint hardware. Call with your VIN and the number off your old sensor and we will match it against the actual build.
Installing the part does not clear the fault. The module holds the code until a scan tool that can talk to the restraint system erases it. If the code comes back on its own after you clear it, the problem is upstream: a connector that is not fully latched, damaged wiring, or a second sensor with the same complaint.
Sometimes. Some makes use mirror-image sensors with separate part numbers for each side. Others use one identical sensor and let the bracket do the handing. The label on your old part is the only reliable answer.
Other parts in the catalogue:
Driver airbag: the module in your steering wheel Passenger airbag: the module behind your dashboard Knee airbags: what they do and how to buy the right one Side curtain airbags Seat side airbags Seat belt retractors All part types
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