Symptom
Collision warning system unavailable
A message that forward collision warning, automatic emergency braking or adaptive cruise control is unavailable, or those functions simply refusing to arm. The car drives entirely normally, which is exactly what makes this worth taking seriously — nothing about the driving experience signals that a safety system has stopped watching the road, and drivers become accustomed to assistance without noticing how much they have come to rely on it.
The systems usually share one forward-looking sensor, so a single fault removes several functions at once, and the dashboard does not always say which. Until it is resolved, assume the car will neither warn nor brake for you.
The commonest cause is not a failure at all: the sensor is blinded by packed snow, ice, mud, heavy road film or something fitted across the front of the car, and reporting itself unavailable is the correct response. Cleaning the area resolves a large share. The next commonest is alignment after front-end work — including damage light enough to leave no visible mark.
Also described as: collision warning not working, aeb unavailable, emergency braking unavailable, adaptive cruise unavailable, driver assist unavailable, pre-collision system unavailable, radar blocked, front assist not available, cruise control unavailable, سیستم هشدار برخورد غیرفعال, aviso colision no disponible, frenada emergencia no disponible, sistema anticolision falla, نظام تحذير التصادم غير متاح, الفرملة الطارئة معطلة, تحذير الاصطدام لا يعمل
What this usually means
The car drives entirely normally, which is exactly what makes this worth taking seriously — nothing about the driving experience signals that a safety system has stopped watching the road, and drivers become accustomed to assistance without noticing how much they have come to rely on it.
The systems usually share one forward-looking sensor, so a single fault removes several functions at once, and the dashboard does not always say which.
Until it is resolved, assume the car will neither warn nor brake for you.
The commonest cause is not a failure at all: the sensor is blinded by packed snow, ice, mud, heavy road film or something fitted across the front of the car, and reporting itself unavailable is the correct response. Cleaning the area resolves a large share.
The next commonest is alignment after front-end work — including damage light enough to leave no visible mark. A parking knock that scuffed a bumper can move a radar enough to matter, and the sensor cannot tell you it is looking three degrees to the left; it can only tell you it is unsure.
A windscreen replacement is the case most often missed, because the camera at the top of the screen has to be recalibrated afterwards and the glass must be the correct specification for it.
And the version that does not report itself is the one that matters most. A system that says nothing and brakes late, or brakes at a shadow, is aiming at the wrong part of the road — which is why calibration after any disturbance is a requirement rather than a recommendation.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Message appears in snow, heavy rain or after a muddy road | The sensor blinded — reporting itself unavailable is the correct response | Clean the front of the car, behind the badge, and the windscreen in front of the mirror. Retest. | No repair. This is the commonest cause and the cheapest to resolve. |
| Unavailable since front-end work or a parking knock | Alignment — including impacts that left no visible mark | Ask what happened rather than looking for damage. A scuffed bumper can move a radar enough to matter. | Recalibrate to the manufacturer's procedure. |
| Unavailable since a windscreen replacement | The forward camera not recalibrated, or glass of the wrong specification | Establish who fitted the screen and whether calibration was carried out. This is the most missed cause. | Recalibrate, and replace the glass if it is not to specification. |
| Several assistance functions unavailable together | One shared sensor rather than several faults | List what has gone. They usually share the forward sensor, and the dashboard does not always say so. | Repair the shared sensor. Do not diagnose each function separately. |
| System brakes unexpectedly, or fails to brake when it should | The version that does not report itself — aiming at the wrong part of the road | Treat as more urgent than an unavailable message. A false intervention at speed is itself a hazard. | Recalibrate and have the sensor checked. This is why calibration is a requirement rather than advice. |
| Unavailable with other unrelated warnings | Supply or network rather than the sensor | Test the battery and charging before diagnosing the sensor, as with every driver-aid module. | Repair the supply, clear and re-scan. |
-
Message appears in snow, heavy rain or after a muddy road
- Likely cause
- The sensor blinded — reporting itself unavailable is the correct response
- How to confirm it
- Clean the front of the car, behind the badge, and the windscreen in front of the mirror. Retest.
- What fixes it
- No repair. This is the commonest cause and the cheapest to resolve.
-
Unavailable since front-end work or a parking knock
- Likely cause
- Alignment — including impacts that left no visible mark
- How to confirm it
- Ask what happened rather than looking for damage. A scuffed bumper can move a radar enough to matter.
- What fixes it
- Recalibrate to the manufacturer's procedure.
-
Unavailable since a windscreen replacement
- Likely cause
- The forward camera not recalibrated, or glass of the wrong specification
- How to confirm it
- Establish who fitted the screen and whether calibration was carried out. This is the most missed cause.
- What fixes it
- Recalibrate, and replace the glass if it is not to specification.
-
Several assistance functions unavailable together
- Likely cause
- One shared sensor rather than several faults
- How to confirm it
- List what has gone. They usually share the forward sensor, and the dashboard does not always say so.
- What fixes it
- Repair the shared sensor. Do not diagnose each function separately.
-
System brakes unexpectedly, or fails to brake when it should
- Likely cause
- The version that does not report itself — aiming at the wrong part of the road
- How to confirm it
- Treat as more urgent than an unavailable message. A false intervention at speed is itself a hazard.
- What fixes it
- Recalibrate and have the sensor checked. This is why calibration is a requirement rather than advice.
-
Unavailable with other unrelated warnings
- Likely cause
- Supply or network rather than the sensor
- How to confirm it
- Test the battery and charging before diagnosing the sensor, as with every driver-aid module.
- What fixes it
- Repair the supply, clear and re-scan.
Codes that produce this symptom (24)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P2583 Cruise Control Front Distance Range Sensor Single Sensor or Centre Typical of this code Moderate
- P2591 Cruise Control Front Distance Range Sensor Left Typical of this code Moderate
- P2592 Cruise Control Front Distance Range Sensor Right Typical of this code Moderate
- U0232 Lost Communication With Side Obstacle Detection Control Module A Typical of this code Moderate
- U0233 Lost Communication With Side Obstacle Detection Control Module B Typical of this code Moderate
- U0235 Lost Communication With Front Distance Range Sensor — Single Sensor or Centre Typical of this code Moderate
- U0243 Lost Communication With Parking Assist Control Module B Typical of this code Moderate
- U0265 Lost Communication With Image Processing Sensor A Typical of this code Moderate
- U0279 Lost Communication With Haptic Control Module Typical of this code Moderate
- U0305 Software Incompatibility With Cruise Control Module Typical of this code Moderate
- U0428 Invalid Data Received From Steering Angle Sensor Module Typical of this code High
- U0433 Invalid Data Received From Front Distance Range Sensor — Single Sensor or Centre Typical of this code Moderate
- U0533 Invalid Data Received From Side Obstacle Detection Control Module A Typical of this code Moderate
- U0534 Invalid Data Received From Side Obstacle Detection Control Module B Typical of this code Moderate
- U053B Invalid Data Received From Image Processing Module A Typical of this code Moderate
- U053C Invalid Data Received From Image Processing Module B Typical of this code Moderate
- U053D Invalid Data Received From Image Processing Module C Typical of this code Moderate
- U0544 Invalid Data Received From Parking Assist Control Module B Typical of this code Moderate
- P057B Brake Pedal Position Sensor A Circuit Range/Performance High
- U0266 Lost Communication With Image Processing Sensor B Moderate
- U0267 Lost Communication With Image Processing Sensor C Moderate
- U0268 Lost Communication With Image Processing Sensor D Moderate
- U0420 Invalid Data Received From Power Steering Control Module A High
- U0461 Invalid Data Received From Audible Alert Control Module Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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