Used Car Buyer’s Guide: Checking if ADAS Works Properly

Buying a second-hand vehicle is always a balance of excitement and caution. With the rise of advanced driver assistance systems (ADAS), that balance becomes even more delicate. Features like lane keeping, autonomous emergency braking and adaptive cruise control are now commonplace, and they add a layer of complexity to your inspection process. The last thing you want is to pay for technology that doesn’t work as advertised or worse, creates a false sense of security. This guide helps everyday drivers assess whether ADAS features on a used car are in good working order before committing to the purchase.

Understand what’s installed

Before you even inspect the vehicle, research the model you are considering. Manufacturers equip different trims with different driver assistance suites, and they sometimes change them between model years. Subaru’s EyeSight, Toyota Safety Sense, Mazda i-Activsense, Ford Co-Pilot360 and others bundle multiple features like forward collision warning, adaptive cruise, lane departure warning and automatic high beams. When reading online reviews or the owner’s manual, make a list of what should be present. This checklist will be your reference during the test drive. If the seller claims the car has certain features that were never offered on that trim, that is a red flag.

Inspect the hardware

ADAS depends on cameras and sensors mounted around the vehicle. A visual check can reveal obvious problems. Look at the windscreen area behind the rearview mirror for camera modules. These are often contained in a plastic housing; cracks or cloudiness on the windscreen in this area can obscure the camera’s view. Examine the front bumper, grille and lower air intakes for radar sensors – they look like small dark panels. Check that there are no cracks, dents or aftermarket modifications that could misalign them. Inspect wing mirrors for blind-spot sensors and rear bumpers for parking radars or cross-traffic alert modules. If the car has been in an accident or had bodywork done, poorly fitted panels may indicate sensors were not reinstalled or recalibrated properly.

Tyres and suspension also affect calibration. Uneven tyre sizes, mismatched tyre pressures or sagging springs change the ride height and can throw off camera angles. When you walk around the car, look for a level stance and matching tyres. Ask the seller about any wheel or suspension modifications. Larger wheels, lowered springs or lift kits can require recalibration of radar and camera angles.

Ask for service and calibration records

Whenever a windscreen is replaced, a front bumper is removed or suspension components are changed, most ADAS systems need recalibration. Legitimate workshops will provide documentation showing that static or dynamic calibration was performed afterward. Ask the owner or dealer for service history related to these items. If they cannot provide proof of calibration after a major repair, you may need to budget for it yourself. Also look for any recorded fault codes or warranty work; repeated ADAS-related repairs could indicate persistent issues.

Use an OBD-II scan tool

Many faults hide behind the dashboard lights. A quick diagnostic scan with a handheld OBD-II tool can reveal stored error codes related to the driver assistance systems. While general scanners may only display generic codes, some advanced consumer-level tools can access manufacturer-specific modules. Plug the scanner into the port under the steering column and check for codes referencing camera alignment, radar obstruction, steering angle sensors or control module malfunctions. If you see active or pending codes, ask the seller to address them or negotiate the price accordingly.

Take a thorough test drive

The most direct way to verify that ADAS features are working is to use them. On a quiet stretch of highway, engage adaptive cruise control and see if it maintains distance smoothly. Listen for chimes or alerts when you drift toward lane markings and observe whether the steering wheel vibrates or nudges back. Try the blind spot monitoring by indicating and passing another vehicle; does the warning light illuminate? Test rear cross-traffic alert and parking sensors in a safe car park. If any feature fails to activate, engages erratically or produces warning messages, that is a sign of trouble. Remember to test in conditions similar to normal driving; heavy rain or bright sun can temporarily disable camera-based systems even if they are healthy.

Pay attention to the instrument cluster. Many cars show icons when systems are active or disabled. An orange or red ADAS icon usually signals a fault. Persistent messages like “Front camera unavailable” or “Radar blocked” suggest maintenance is needed. Resetting the car between test drives can sometimes clear temporary errors, so if the warning returns after a few minutes, it is more than a fluke.

Don’t forget your own senses

While the seller might focus on showing you that the technology works, stay aware of the driving experience. If the steering feels heavy or pulls to one side, the alignment could be off, affecting lane keeping performance. If braking distances feel long or inconsistent, the automatic emergency braking sensor might not be calibrated. A clunky ride, uneven suspension or mismatched tyres can all interfere with sensor accuracy.

Negotiate or walk away

If you discover faults, you have two options: ask for the issues to be repaired and recalibrated before purchase, or negotiate a lower price to cover the cost. Calibration can range from a few hundred to over a thousand dollars depending on the system and vehicle. Remember that you cannot calibrate at home without professional equipment. If the seller refuses to address the problems or claims the systems “naturally” misbehave, it may be safer to walk away.

Conclusion and further reading

Buying a used car with ADAS features requires diligence, but it also empowers you to enjoy a safer driving experience once you understand what to look for. By researching the model’s technology, inspecting the hardware, checking service records, scanning for fault codes and performing a hands-on test, you can confidently assess whether the car’s driver assistance systems are fit for purpose. For more insight into situations where these systems may let you down, read our article on when not to trust your ADAS, and learn about the top override moments every driver should expect. These resources will help you make an informed purchase and stay safe on the road.