Cat S and Cat N ADAS Calibration
If you bought a Cat S or Cat N vehicle, the collision damage that caused the write-off almost certainly displaced one or more ADAS sensors. From our data, 6% of calibration enquiries come from salvage vehicle buyers who discovered their car's safety systems aren't working correctly. Here is what you need to know before driving it.
Why Salvage Vehicles Need ADAS Calibration
Every Cat S and Cat N vehicle was in a collision severe enough for an insurer to declare it uneconomical to repair through their network. Cat S means structural damage - chassis, crumple zones, structural pillars. Cat N means non-structural damage - panels, bumpers, lights, mechanical components. Both categories involve impacts that are guaranteed to have moved at least one ADAS sensor from its factory position.
The repair shop that rebuilt the vehicle may have replaced the bumper, fixed the panels and made the car look perfect. But ADAS calibration requires specialist equipment that most salvage repair shops don't have. The sensors were moved in the crash. The bodywork was fixed. The sensors were never recalibrated. This is the default state of most salvage vehicles entering the used market.
What Write-Off Categories Mean for ADAS
Cat S (Structural). The vehicle's structural frame was damaged. This means the sensor mounting points - the parts of the body that hold the radar, cameras and blind spot sensors in position - may have been bent, welded or replaced. Even after repair, the geometry of the mounting points may not match factory specification. Full ADAS diagnostic scan and recalibration are mandatory.
Cat N (Non-structural). Panels, bumpers and non-structural components were damaged. The front bumper is the most common repair on Cat N vehicles - and the front radar sits behind the bumper on most cars. A new bumper with a shifted radar bracket means the radar is pointing in the wrong direction. Camera systems are affected if the windscreen was replaced or the A-pillar flexed during the impact.
Both categories share the same ADAS risk: sensors displaced during the collision, bodywork fixed to cosmetic standard, sensors never recalibrated to functional standard.
Red Flags When Buying a Salvage Vehicle
No calibration certificate in the history. If the vehicle was repaired after a collision and there's no ADAS calibration certificate in the documentation, the sensors were not recalibrated. Ask the seller for the calibration paperwork. If they can't provide it, assume the ADAS needs doing.
ADAS warning lights on the dashboard. Obvious, but worth stating. Test drive the vehicle and check for any ADAS warning messages - "Front Assist not available", "Pre-Collision System Malfunction", "Driving Assistant Inactive". If any appear, the ADAS was not recalibrated after repair.
No warning lights but systems behave oddly. More dangerous than visible warnings. Adaptive cruise control that tracks erratically, lane keeping assist that pulls toward one side, or AEB that activates for no reason (phantom braking) all indicate sensors that are operating but misaligned. The system passed its power-on self-test but fails under real driving conditions. This is the silent failure mode that Stellantis vehicles in particular are known for.
Aftermarket windscreen fitted during repair. Many salvage rebuilds use aftermarket glass to save cost. On Honda and Acura vehicles, aftermarket glass produces only a 30% camera calibration success rate. On Audi, aftermarket glass is formally rejected by the manufacturer for ADAS vehicles. If aftermarket glass was fitted, camera calibration may fail until OEM glass is installed.
What We Check on Cat S and Cat N Vehicles
A full-system diagnostic scan covers every ADAS module in the vehicle - not just the visibly damaged area. We scan chassis, body and network control units to identify every stored fault code, every pending code, and every module in a degraded state.
This matters because collision damage cascades. A front-end impact that broke a MAP sensor can cascade through the CAN bus to affect blind spot sensors at the rear of the vehicle. A windscreen replacement during the rebuild may have left the forward camera uncalibrated even if the front of the car wasn't damaged. A battery disconnection during the repair may have put the ADAS control unit into a reset state.
After the diagnostic scan, we calibrate every system that is out of specification. Front camera, front radar, rear blind spot sensors, parking sensors, surround-view cameras - whatever the vehicle has and whatever the collision displaced. The result is a vehicle with every ADAS system functioning to manufacturer specification, documented with an IMI-certified calibration certificate.
Cost and What to Expect
Most Cat S and Cat N vehicles need a full system reset rather than a single sensor calibration, because the collision typically displaced multiple sensors. Full system reset starts from £499 and includes the diagnostic scan, calibration of every affected system, post-scan verification and calibration certificate.
If only one system is affected - for example a rear-only impact on a Cat N vehicle that only displaced the blind spot sensors - the cost is lower. Radar calibration starts from £349. Camera calibration from £199. We confirm the scope and fixed price after the initial diagnostic scan.
For full pricing details, see our cost guide. For more on what happens after collision repair, see our collision calibration guide. For understanding the fault codes the diagnostic scan may reveal, see our error codes guide.
Cat S and Cat N ADAS Calibration — Common Questions
Answers to frequently asked questions on this topic
There is no legal requirement to calibrate ADAS before driving a salvage vehicle. However, the collision that caused the write-off almost certainly displaced sensors. Driving with miscalibrated ADAS means your safety features are either non-functional or operating with unknown error margins. If uncalibrated ADAS contributes to an accident, it could affect your insurance position.