Forward Collision Warning Fault: What It Means and What to Do
Forward Collision Warning, FCA on Hyundai, Pre-Collision System on Toyota, Active Brake Assist on Mercedes, Forward Collision Assist on Stellantis. Same fault, different dashboard text on every modern make. The radar or camera that runs automatic emergency braking has lost its aim. Here's what's actually happening, what to check first, and what the recalibration costs.
Safe to drive, but the auto-brake is off
Forward collision warning, however it's badged on your dash, is the automatic emergency braking system. While it's flagging a fault, it won't intervene if traffic stops sharply ahead. Normal brakes, steering and conventional cruise all still work. Leave more following distance and treat it as a system that isn't there until it's sorted.
Why the warning trips on every make
Every manufacturer brands this fault differently. Hyundai-Kia calls it Forward Collision-Avoidance Assist (FCA). Toyota calls it Pre-Collision System (PCS). Mercedes calls it Active Brake Assist. Honda calls the umbrella Honda Sensing. Stellantis brands (Jeep, Alfa Romeo) stick with FCW or 'Service FCW system'. The wording on your dash points to your make's marketing team, not the cause of the fault.
The cause is the same across all of them. A forward-facing radar behind the front grille and a camera at the top of the windscreen feed the system, and their aim is set to a fraction of a degree.
A bumper repair, a refitted grille, a parking knock, a new windscreen, even a wheel alignment without a follow-up ADAS reset, any of those shifts the aim enough to take the system offline. The car flags the warning it has.
Pick your make
Make-specific naming, pricing and the model-level pattern we see on each.
- By makeRead more
Hyundai
Forward Collision-Avoidance Assist (FCA) on the IONIQ, Kona and Tucson.
- By makeRead more
Nissan
Forward Collision Warning paired with Intelligent Cruise Control (ICC) on the Qashqai and Juke.
- By makeRead more
Toyota
Pre-Collision System (PCS) on the Corolla, C-HR and RAV4.
- By makeRead more
Honda
Honda Sensing suite (covers ACC, Lane Assist and Collision Mitigation) on the Civic and CR-V.
- By makeRead more
Mercedes
DISTRONIC and Active Brake Assist on the A-Class, GLC and EQE.
Try these checks first
- 1
Look at the radar area
The forward radar sits behind the front grille badge on most cars. Look for visible damage, a bumper that's sitting off-square, or debris packed into the grille. A cracked badge or a popped clip is enough to throw the warning.
- 2
Wipe the sensor face and the camera zone
Road grime, packed snow, or insect debris on the radar housing can trigger a temporary fault. Use a damp cloth on the badge area. Use a clean dry cloth on the inside of the windscreen behind the camera. Drive 10 minutes and check.
- 3
Think back through the last 4 weeks
New windscreen, bumper repair, front-end knock, badge change, wheel alignment. Any of those without a follow-up ADAS calibration is the most likely cause we see. Note the date for the workshop.
- 4
Cycle the ignition and drive on a clear road
Switch the car off, lock it, wait 60 seconds, restart. Drive 10 minutes on a clear road with lane markings, ideally above 40 mph. Some systems run a self-check on a steady drive and clear the warning. If it stays or returns, the sensor needs recalibrating.
How we fix it
If the checks above don't sort it, the radar or camera needs recalibrating. A technician realigns the sensor to the manufacturer's reference, clears the stored fault, and confirms the safety systems are reading the road again before you leave.
Most cases run as a static calibration: target boards positioned in front of the car at the correct standoff, OBD-linked alignment routine, post-scan to confirm. Some makes also need a dynamic drive at steady speed before the system locks. Your accredited workshop runs whichever applies.
It's a fixed-fee job and ends with a calibration certificate. The full procedure is in our ADAS calibration guide.
Frequently asked questions
Front-end work is the single biggest trigger we see across every make. Bumper repair, radar bracket removal, a front-end knock, a new windscreen, or a wheel alignment without a follow-up ADAS reset.
Any of those shifts the radar or camera aim enough to take the system offline. If the warning appeared within a few weeks of any of those, that's the cause.
Radar calibration is a fixed £349 across our accredited network, the same wherever you are in the UK. That covers the diagnostic scan, the calibration, and a calibration certificate.
If the fault involves the windscreen camera as well, the windscreen tier is £199. A full-system reset covering multiple ADAS modules at once is £499.
Most calibrations take 60 to 120 minutes in the workshop. If your car needs both static target work and a dynamic drive (some Toyota and Honda platforms), allow up to a half-day. Your accredited workshop confirms the expected duration when you book.
Almost always one underlying fault. The forward radar and the front camera feed Forward Collision Warning, adaptive cruise, lane assist and emergency braking from the same readings. When the radar's aim is off, several systems flag the loss of confidence at once. A single calibration visit usually clears them together.
In most cases, yes. The calibration restores the radar or camera to its manufacturer aim, and the fault clears.
Two situations to flag. If the sensor itself was damaged in the trigger event, not just knocked out of aim, it needs replacing before the calibration will hold. And if the calibration passes on the tool but the warning returns within a few drives, a post-scan tells us what's still wrong before you pay twice.
Static calibration needs a level floor, controlled lighting, and a target board placed at an exact distance in front of the car. That's typically a workshop bay. Some parts of the job can be done on-site where conditions allow, a level driveway, controlled light, enough space. We confirm what's available near your postcode when you book.
Book your collision-system calibration
Send your registration and what's been done. We come back with the tier, the nearest accredited workshop, and the soonest slot.