Fuel Pump Switch: Your Essential Guide to Safety, Function, Troubleshooting, and Use

Understanding your vehicle's fuel pump switch is crucial for safety, diagnosing common problems, and performing essential maintenance. This switch serves as a critical safety device designed to cut power to the fuel pump immediately in the event of an accident, potentially preventing catastrophic fires. Knowing where it is located, how to check it, reset it if tripped, and when it might need attention can save you significant time, money, and frustration.

What is a Fuel Pump Switch and Why is it Critical?

Often referred to as an "inertia switch," a "fuel pump shut-off switch," or an "impact switch," the fuel pump switch is a vital safety component in modern vehicles. Its primary purpose is to interrupt the electrical power supply to the electric fuel pump when it detects a sudden, significant impact – the kind that typically occurs during a collision.

How it Enhances Safety: Gasoline is highly flammable. In a collision, fuel lines, the fuel tank, or the pump itself can rupture. If the electric fuel pump continues to operate after such damage, it could spray pressurized fuel onto hot engine components, electrical sparks, or exhaust parts, creating an extreme fire hazard. The fuel pump switch acts as a failsafe, cutting power to the pump instantly upon impact, significantly reducing this risk.

Basic Operation: Inside the switch is a small weight or pendulum mechanism. Under normal driving conditions, this mechanism is stable, allowing electrical current to flow through the switch to the fuel pump. When subjected to a sudden jolt or deceleration equivalent to the force of an impact (e.g., hitting a curb hard, a collision), the internal mechanism moves rapidly. This movement typically triggers a spring-loaded switch that snaps open, breaking the electrical circuit and stopping the fuel pump dead. Think of it as an emergency circuit breaker for your fuel system.

Where is the Fuel Pump Switch Located? Finding the Vital Cutoff

The fuel pump switch is deliberately placed in an area likely to experience minimal damage during a typical frontal or side impact, away from crumple zones. Its exact location varies significantly between vehicle makes, models, and years, but common areas include:

1. Within the Trunk/Cargo Area: This is perhaps the most frequent location, especially in passenger cars and SUVs. Look in one of these spots:
   • High on the rear panel behind the trunk liner/carpet (often near the latch mechanism).
   • Behind the trunk side trim panels (left or right).
   • Beneath the rear package shelf trim.
   • Sometimes near the spare tire well.
2. In the Passenger Compartment (Near Front Seats): Common locations include:
   • Behind kick panels on the passenger or driver's side (the panels below the glovebox or below the steering column).
   • Mounted to the firewall on the passenger or driver's side (accessible from inside the cabin after removing trim).
   • Under the carpet near the front seats.
   • Attached to the center console frame inside the console.
3. In the Engine Bay (Less Common, More Protected Area): If present here, it will usually be high on the firewall within the passenger compartment part of the firewall or very close to it, protected somewhat by fenders or structural members. This is less common than interior locations.
4. Under Seats: Less frequent, but sometimes found mounted beneath the passenger or driver's seat.

Crucial: Never start looking blind! Consult your vehicle's owner's manual. The specific location will be detailed in the index, often under sections like "Fuses," "Fuel Pump," "Emergency Procedures," "Roadside Emergencies," or "Inertia Switch." Online vehicle-specific forums or factory service manuals (available from publishers like Haynes or Chilton, or dealer sources) are also excellent resources for finding exact locations and access steps. Physically, look for a small, round or rectangular plastic device, often about 1-3 inches in diameter/width, with a distinct red or black button on top for resetting.

Why Might the Fuel Pump Switch Trip? More Than Just Accidents

While its primary design function is for collision safety, a fuel pump switch can sometimes be triggered by events other than major accidents. Understanding these scenarios helps with diagnosis:

1. Severe Impacts (Design Intent):
   • Collisions involving other vehicles or stationary objects.
   • Hitting large potholes, curbs, or road debris with significant force, especially if impacting wheels/suspension.
   • Driving off-road over very rough terrain with hard jolts and jarring.
2. Unusually Hard Braking or Manoeuvres: While designed not to trip during normal driving, extremely sudden and forceful braking (like emergency stops) or sharp, violent swerving manoeuvres might occasionally trigger it, though this is less common and sometimes indicates an overly sensitive or worn switch.
3. Mechanical Disturbance: Physical jarring of the switch itself can cause it to trip. This could happen during:
   • Rough handling of objects placed in the trunk or cargo area, particularly near the switch location. Dropping a heavy bag or cargo item directly onto the switch area.
   • Vigorous vacuuming or cleaning inside the trunk/cargo area where the switch is located.
   • Bodywork or interior repair that involves hammering, panel removal, or forceful adjustments near the switch.
4. Age-Related Wear or Sensitivity: Over many years, the internal mechanism of the switch (springs, dampening materials) can weaken or become sticky. This can make it potentially more susceptible to tripping during events less severe than intended (like driving over railroad tracks more aggressively, but not violently). It can also sometimes cause the switch not to reset properly after a legitimate trip.
5. Faulty Switch: Like any electrical component, the switch itself can fail internally. Corrosion, internal breakage, or electrical failure can cause it to trip and not reset, or conversely, not trip when it should. This is less likely than external causes but becomes more probable with very high mileage or age.

Symptoms: How to Tell if Your Fuel Pump Switch Has Tripped

The most obvious symptom of a tripped fuel pump switch is a complete lack of power to the fuel pump, resulting in the engine failing to start or suddenly stalling immediately after an impact event. Key indicators include:

1. Cranking But No Start (Most Common): When you turn the ignition key to the "Start" position, the starter motor cranks the engine (you hear it turning over), but the engine does not fire up. This happens because fuel isn't being delivered to the engine.
2. Sudden Engine Stall After Impact: Driving along, then you hit something significant (pothole, curb, debris), and the engine immediately dies and cannot be restarted.
3. No Fuel Pump "Buzz" at Ignition: When you first turn the ignition key to the "On" or "Run" position (before starting), a healthy fuel pump will typically run for a few seconds to pressurize the system. It creates a faint humming, buzzing, or whining sound, often audible from the rear seat or trunk area, or near the fuel tank. If you do NOT hear this brief priming sound, it strongly suggests no power is reaching the fuel pump – a tripped inertia switch is a prime suspect.
4. No Other Obvious Causes: Often, this happens suddenly without other warning signs like a "Check Engine" light (though related codes might appear later if scanned). It feels specifically connected to a jarring event or occurs without prior symptoms of a failing fuel pump (like sputtering, power loss under load, or persistent long cranking times).
5. Recent Activity Near the Switch Location: If you were just loading/unloading heavy items in the trunk or performing interior work near where the switch is housed, and the car won't start afterward, the switch should be checked immediately.

Important: While a tripped fuel pump switch is a common and relatively simple cause of the "cranks but no start" symptom, it is not the only possible cause. Other issues like a failed fuel pump itself, a blown fuel pump fuse or relay, severely low fuel levels, ignition system problems, or a dead battery can mimic the same symptoms. Resetting the inertia switch is a quick diagnostic step, not a guaranteed fix for every no-start condition.

How to Safely Check and Reset a Tripped Fuel Pump Switch: Step-by-Step

Resetting a tripped fuel pump switch is usually very straightforward, but safety is paramount due to the involvement of flammable fuel vapors.

Safety Precautions First:

• Vehicle Off: Ensure the ignition is completely off. Remove the key if possible.
• Parking Brake Engaged: Set the parking brake firmly.
• Neutral/Park: Place an automatic transmission in "Park." Place a manual transmission in Neutral.
• Well-Ventilated Area: Perform the reset outdoors or in a well-ventilated garage. Avoid enclosed spaces.
• No Ignition Sources: Absolutely no smoking, flames, sparks, or electronic devices that could spark nearby. This includes mobile phones. Gasoline vapors are explosive and heavier than air; they can linger and travel considerable distances.
• Identify Location: Consult your owner's manual to positively identify the exact location and access method for your vehicle's specific switch. Do not guess.

Resetting Procedure:

1. Locate the Switch: Based on your research, access the switch. This usually involves pulling back trunk/cargo area carpeting/lining, removing a small access panel, or prying off a cover if present. You may need to gently pull away some interior trim panels. Be careful not to damage clips or trim pieces unnecessarily.
2. Identify the Reset Button: Once you see the switch housing, look for a clearly identifiable button on its top or side. This button is almost always red, though sometimes it may be black. It will stand out from the housing. There might be a label saying "Reset," "Fuel Reset," "Push To Reset," or something similar.
3. Press the Reset Button Firmly: Using your finger or thumb, press the reset button straight down firmly and release it. You will usually feel or hear a distinct audible "click" as the internal spring re-engages the electrical contacts inside the switch. This click is a good indicator the reset has worked. In some cases, pushing the button down requires more force than expected. Avoid using tools unless absolutely necessary and only if specified in your owner's manual, as excessive force can damage the switch.
4. Verify Access: Ensure the button stays down (it shouldn't pop back up immediately if pressed correctly). It doesn't require holding it down for any period; a firm press and release is sufficient.
5. Reposition Trim/Lining: Carefully reposition any trunk liners, carpet, or trim panels you moved out of the way. Ensure nothing is pinched or obstructing the switch.
6. Test the System: Get into the driver's seat. Do NOT start the engine yet.
   • Turn the ignition key to the "On" or "Run" position (not "Start"). Listen carefully near the rear of the vehicle or by the fuel tank filler neck. You should hear the fuel pump run for about 2-5 seconds as it pressurizes the fuel system. That priming sound is a strong indicator that power is restored.
   • If you hear the priming sound, attempt to start the engine normally. It should start and run.

What if Resetting Doesn't Work?

• Verify Click: Did you definitely feel/hear the reset button click? Try pressing it more firmly.
• Confirm Location: Double-check you've found the correct switch using your manual/sources.
• Check Fuses and Relays: Resetting the switch doesn't fix underlying electrical faults. Locate your vehicle's fuse box(es) (see manual). Find the fuse specifically designated for the fuel pump (usually labeled "Fuel Pump," "FP," or "Fuel"). Pull it out and inspect the thin metal strip inside. If it's visibly broken or melted, the fuse is blown and needs replacement with the identical amperage rating. Also, find the fuel pump relay. Relays can sometimes fail internally, preventing power from reaching the fuel pump circuit. Try swapping the fuel pump relay with an identical relay from another non-critical system in the fuse box (like the horn or A/C relay – consult manual). If the car starts with the swapped relay, the original fuel pump relay is faulty.
• Fuel Level: Ensure there's sufficient fuel in the tank. Gauges can malfunction. Add a gallon or two of fuel.
• Mechanical Fuel Pump Failure: If power is confirmed (primer sound heard), but the engine still won't start after resetting the switch and checking fuses/relays, the fuel pump itself may have failed coincidentally or been damaged in the initial impact that tripped the switch. Further diagnosis is needed.
• Damaged/Faulty Switch: If the reset button doesn't click, or clicks but still doesn't restore power to the pump (no priming sound, engine won't start), and you've eliminated fuse/relay issues, the inertia switch itself may be mechanically damaged or electrically faulty and require replacement. If it trips repeatedly without significant cause, this also indicates a faulty switch.
• Other Electrical Faults: Wiring issues between the ignition switch, inertia switch, fuse/relay center, and fuel pump can cause interruption. If not comfortable tracing wiring, seek professional help.

When Resetting is Insufficient: If the car starts after resetting the switch but the problem recurs frequently without any significant impact, this strongly points towards an internal fault within the switch itself. The mechanism may be worn or overly sensitive. Replacement is the solution.

Replacing a Faulty Fuel Pump Switch: When DIY Might Be Possible

A malfunctioning fuel pump switch that trips repeatedly or fails to reset reliably needs to be replaced. While access can sometimes be challenging depending on location, the actual replacement process is typically straightforward electrically.

Procedure Outline:

1. Verify Need: Confirm the switch is faulty (frequent tripping, won't reset properly, physically damaged). Ensure fuses/relays are intact.
2. Locate Exact Replacement Part:
   • Dealer Parts Department: Provide your vehicle's VIN to ensure getting the correct, OEM switch. Best guarantee of fit and function, but potentially most expensive.
   • Reputable Auto Parts Store: Look for major brands (like Standard Motor Products, BWD, etc.). Provide the make, model, year, and engine size. Counter staff can assist.
   • Online Retailers: Ensure they specify exact fitment for your vehicle. Compare prices, but be cautious of obscure brands.
3. Safety Preparations: Follow all safety precautions listed in the reset section (ignition off, parking brake, ventilation, no sparks).
4. Access the Switch: Carefully remove any necessary interior trim, carpeting, or panels to gain full, unobstructed access to the switch. Pay attention to clip locations to avoid breakage.
5. Disconnect the Electrical Connector: The switch will have a wiring harness connector plugged into it. This usually has a locking tab. Depress the locking mechanism firmly and pull the connector straight off the switch terminals. Avoid pulling on the wires themselves. Some force might be needed.
6. Remove the Old Switch: The switch is typically held in place by one or two mounting bolts, clips, or sometimes integrated into a bracket. Remove the fasteners carefully. If clips are present, gently pry them open using trim tools or small screwdrivers. Note the orientation of the switch.
7. Install the New Switch: Position the new switch exactly as the old one was removed. Reinstall the mounting bolts/clips securely. Do not overtighten bolts on plastic housings/brackets.
8. Reconnect the Electrical Connector: Align the connector properly with the switch terminals and push it firmly and straight onto the switch until you hear and feel the locking tab click or snap into place. Tug gently to ensure it's secure.
9. Reassemble: Carefully reposition any removed trunk liners, carpets, trim panels, or covers, making sure everything clips or fastens back securely. Double-check nothing is pinching wires or obstructing the new switch.
10. Test: Turn the ignition to the "On" position and listen for the fuel pump priming sound. If present, start the engine. It should run normally. Avoid deliberately testing the switch function with impacts!

Complex Access: In some vehicles, accessing the switch can be particularly difficult – buried deep behind dashboards, requiring significant seat or center console removal, or integrated into complex wiring modules. If you feel uncomfortable with the level of disassembly required, seek assistance from a professional mechanic. Their expertise and specialized tools can save considerable time and prevent accidental damage to expensive interior components. Remember, the fuel pump switch is a critical safety device. Ensure a replacement is done correctly.

Interaction with Other Systems: Beyond the Simple Cutoff

The fuel pump switch doesn't exist in isolation; it interacts with other vehicle systems primarily related to theft prevention and engine management:

1. Anti-Theft Systems (Immobilizers): Many modern anti-theft systems disable engine operation if an unauthorized key is used by cutting the fuel pump circuit or the starter circuit. While not the inertia switch itself causing the disablement, both scenarios result in a lack of fuel pump operation. This can sometimes cause confusion.
   • Key Distinction: A tripped inertia switch always has a direct cause (impact, severe jolt, interference). An anti-theft system preventing the pump from running is triggered by the key or key fob not being recognized. If resetting the inertia switch doesn't fix a no-start and the anti-theft light is flashing, suspect the key/immobilizer system.
2. Engine Control Module (ECM/PCM): The vehicle's computer controls the fuel pump relay based on signals from the ignition switch and other sensors. The inertia switch is wired in series between the relay (or sometimes directly into the circuit) and the fuel pump. Its sole function is a safety override. The ECM generally doesn't directly monitor the inertia switch status and won't typically set a specific "inertia switch tripped" diagnostic trouble code (DTC). However, it will detect the result of the switch tripping:
   • When the switch trips, power to the fuel pump cuts off instantly.
   • The ECM expects the fuel pressure to be within a certain range (monitored by the fuel pressure sensor). When fuel pressure drops to zero unexpectedly and the engine stalls without other detected faults, the ECM might set generic codes related to fuel delivery issues.
   • Common related codes include P0087 (Low Fuel Rail Pressure), P0193 (Fuel Rail Pressure Sensor Circuit High Input - sometimes indicating sudden loss of signal/function), or codes related to engine misfires across all cylinders (P0300) because no fuel is delivered. Resetting the inertia switch often resolves these codes, though you may need to drive a cycle for them to clear. They don't directly point to the inertia switch itself.

Troubleshooting Tip: If you pull codes related to fuel delivery or engine stalls immediately after an impact event, always check the fuel pump inertia switch as your first step before delving deeper into the fuel system or ECM diagnostics. It's often the simple, overlooked fix.

Importance of Correct Diagnosis: Why Jumping to Conclusions Costs Money

Misdiagnosing a tripped fuel pump switch as a failed fuel pump is a common and potentially expensive mistake. Consider:

1. Cost Differential:
   • Switch Reset: Takes 1-5 minutes. Cost: $0.
   • Switch Replacement: Part cost is usually $20-$80. DIY labor: 15 mins to 2 hours (depending on access). Shop labor: Often 0.5 to 1.5 hours plus parts.
   • Fuel Pump Replacement: Part cost $150-$500+ (especially for integrated pump/module assemblies). DIY labor involves significant work (usually dropping the fuel tank or accessing it under the rear seat). Shop labor: Often 2-5 hours plus expensive parts. Total cost easily $500-$1200+.
2. Wasted Time: Hours spent unnecessarily dropping a tank, diagnosing wiring, or waiting for parts when a simple reset or $40 part was the answer.
3. Unnecessary Risk: Dropping a fuel tank carries inherent risks – damaging fuel lines, spilling fuel, damaging level senders, creating sparks near flammable vapors. It should only be done when necessary.
4. Other Causes Are Possible: Ignoring basic checks like the inertia switch means you might also miss other simple and cheaper causes like a blown fuse, failed relay, wiring issue elsewhere, or even just low fuel level.

Diagnostic Strategy: Always start with the simplest, least invasive, and cheapest potential causes first:

1. Listen for the fuel pump prime at ignition "On". If you hear it, your no-start is not a lack of fuel pump power.
2. If you don't hear the fuel pump prime and there was a recent impact event or disturbance near the switch location, check and attempt to reset the inertia switch.
3. Check the fuel pump fuse visually. Replace if blown.
4. Test/swapthe fuel pump relay.
5. Only after eliminating these simple electrical steps should you move towards diagnosing the pump itself or more complex ECM/wiring issues. The inertia switch reset is step one for a very specific, common symptom pattern.

Understanding the Switch in Modified Vehicles

For vehicle enthusiasts involved in performance modifications or racing:

1. Safety First: Be extremely cautious about disabling or relocating the inertia switch. It exists for critical life-saving reasons. Removing it significantly increases the risk of post-collision fire. Think carefully about the trade-offs.
2. Relocation: Sometimes the stock location conflicts with a race cage, fuel cell, relocated battery, or other modifications. If relocation is absolutely necessary:
   • Mount it securely in a location less susceptible to minor impacts but still able to detect a significant collision force. Avoid isolation mounts that dampen vibration excessively.
   • Ensure the chosen location doesn't place it in immediate danger during minor bumps or contact.
   • Use high-quality wiring connectors and secure routing to avoid chafing or accidental disconnection.
   • Label it clearly so others know its function.
3. Switch Replacement: Some racing regulations may require specific certified inertia switches. Check your sanctioning body's rules.
4. Testing: Never deliberately trigger the switch with gasoline vapors present! If you need to verify its function during testing (a rare requirement), ensure the engine bay and fuel tank area are completely cool and ventilated. Press the reset button while an assistant listens for the pump prime (ignition on, engine off). Or, use a multimeter to check continuity/resistance across the switch terminals while simulating an impact (pressing the reset button changes the switch state). Always assume the switch could trip unexpectedly during aggressive driving.
5. Bypassing (High Risk): Understand that bypassing this switch is essentially disabling a federally mandated safety device. If done for competition purposes where regulations might allow it (rarely) or for troubleshooting, it must be done with extreme care:
   • Use a dedicated fuse specifically rated for the fuel pump circuit at the bypass point.
   • Disconnect the battery before performing wiring work.
   • Solder and seal connections properly; never rely solely on tape or crimp connectors prone to failure in harsh environments.
   • Mark the bypass wiring prominently and document it permanently. Warn any future owners or technicians working on the vehicle. This is critically important for first responders.

The Bottom Line: The fuel pump switch is a vital safety feature designed to protect occupants. Tampering with it in street vehicles is strongly discouraged. For race vehicles, ensure any modifications adhere to safety regulations and are performed professionally with clear documentation of the changes.

Fuel Pump Switch vs. Fuse vs. Relay: Understanding the Circuit

It's helpful to understand how the inertia switch fits within the broader electrical system powering the fuel pump:

1. Fuse: A fuse is a safety device designed to protect the wiring harness from catching fire in the event of an overcurrent situation (like a short circuit). Its thin metal link melts ("blows") if current exceeds its rating, physically opening the circuit. A blown fuse permanently breaks the circuit until replaced. Located in fuse boxes.
2. Relay: A relay is an electromagnetically operated switch. It allows a small current from the ignition switch (command circuit) to control a much larger current required by the fuel pump (load circuit). Think of it as a remote-controlled switch. The ECM usually controls the relay coil. When energized by the ECM (key "On" for priming, and while cranking/running), the relay closes its internal contacts, allowing power to flow from its main power source (fused battery power) through the relay towards the fuel pump. If the ECM signals "off," the relay opens, cutting power. Located in fuse boxes or relay centers.
3. Fuel Pump Switch (Inertia Switch): As discussed, this is a mechanically triggered safety switch wired in series between the power source (which comes from the relay's output terminal) and the fuel pump itself. Its function is independent of the ECM and the relay's normal operation. It only interrupts power when the mechanical trigger is activated (impact force). When functioning normally, it acts as a simple conductor in the circuit unless tripped.

Power Flow Simplified:

1. Battery -> Main Power Fuse
2. -> Fuel Pump Relay (Power Input Terminal)
3. [When relay energized by ECM/ignition]: Power flows from Relay Output Terminal
4. -> Fuel Pump Inertia Switch
5. -> Fuel Pump
6. -> Ground

• A blown fuse stops power before it even reaches the relay or inertia switch. No power anywhere downstream.
• A failed relay (coil failure or contacts stuck open) stops power from flowing to the inertia switch and pump.
• A tripped inertia switch stops power from flowing after the relay (i.e., the relay closes, but power stops at the inertia switch).
• A failed fuel pump stops at the pump, even though power arrives.

This series arrangement means a problem with any one of these components (fuse, relay, inertia switch, pump) will stop the fuel pump from running. Resetting the inertia switch only fixes a problem with itself if it was the point of failure (due to being tripped or internally faulty).

Long-Term Maintenance and Prevention

While the fuel pump switch generally requires no routine maintenance, there are steps to maximize its reliability and prevent nuisance trips:

1. Know Its Location: Familiarize yourself with where the switch is housed in your specific vehicle. Keep your owner's manual accessible in the car or stored digitally.
2. Physical Protection: Be mindful of this location when loading heavy or sharp objects into the trunk or cargo area. Avoid placing items directly on top of the switch housing area. Don't drop heavy items onto cargo floors near the switch. Use caution when vacuuming or cleaning in its vicinity to avoid accidental bumps.
3. Avoid Unnecessary Impact: While you can't avoid all potholes, driving more deliberately over known rough road sections or obstacles can reduce the chance of a trip. If driving off-road is regular, understand that harder jolts are more likely to trigger it.
4. Handle Reset Carefully: When resetting, press the button firmly and directly. Avoid prying or using tools unless specified, and only apply reasonable force. Forcing it can break internal components.
5. Visual Check: If accessible during other maintenance (like replacing a trunk liner), give the switch a quick visual inspection. Look for signs of:
   • Damage: Cracks in the housing, obvious impact marks, bent mounting brackets.
   • Corrosion: On the wiring connector pins or switch terminals (especially in humid climates or areas with road salt). If minor corrosion is visible, disconnect the battery, then carefully clean the terminals with electrical contact cleaner and a brass brush.
   • Water Intrusion: Signs of water staining or moisture inside the switch housing or connector. Ensure surrounding seals or liners are intact to prevent water entry. This is more critical for switches located within trunks prone to leaks or exposed areas under seats.
   • Loose Mounting: Is the switch itself loose or rattling? A loose switch is more likely to trip from minor vibrations.
6. Address Recursive Tripping: If the switch trips repeatedly without a clear, significant cause, do not ignore it. This indicates a likely internal fault or sensitivity issue. Replace the switch promptly. Relying solely on resetting ignores the potential safety risk of a faulty component.
7. Consider Age: For vehicles over 15-20 years old with high mileage, proactively knowing the switch location and having the part number on hand (or even pre-purchasing a replacement for inexpensive parts) can be wise. Age can weaken internal springs and dampeners.
8. First Responder Awareness: Consider adding a small, discrete but noticeable label near the fuel pump cover (gas cap) or inside the fuel door indicating "Fuel Pump Cutoff Switch in Trunk" or similar. This helps firefighters quickly locate and disable power to the fuel pump in an emergency situation involving fire.

By understanding the function, location, and simple maintenance steps related to your vehicle's fuel pump switch, you empower yourself to handle a common cause of unexpected no-start conditions quickly and safely. Remember to always prioritize safety around fuel systems, and let this critical safety device do its important job of protecting you and your passengers.