Symptom
Parking sensors not working
The parking sensors have stopped detecting, beep constantly, or refuse to arm when reverse is selected.
Check the free things first, because they are the commonest causes by a distance. Mud, ice and packed snow across the sensor faces stop them working entirely, which is why these faults appear in winter and clear at a car wash. Anything fitted in the sensing area — a towbar, a bike rack, a tow eye cover, a thick number plate surround — is detected exactly as designed and reported as a permanent obstruction.
Then ask whether the bumper has been painted or replaced. A sensor has to vibrate through its own face, and one extra coat of paint is enough to silence it. A bumper resprayed with the sensors left in place is a classic and entirely invisible cause.
The pattern tells you where to look. Constant beeping the moment reverse is selected means one sensor is reporting something permanently in front of it — and which corner it sounds for usually identifies which sensor. Nothing at all, on any sensor, points instead at the module, its supply or its wiring.
Remember what ultrasound is bad at, because it is not a fault. Soft surfaces, sloped bollards, thin posts and angled walls reflect the chirp away rather than back, so they can genuinely be missed — the system is an aid to looking, not a substitute for it. Heavy rain on the bumper produces false readings for the same reason.
Also described as: parking sensors beeping constantly, reversing sensors not working, pdc not working, park assist not working, parking sensors always beeping, سنسور دنده عقب کار نمیکند, سنسور پارک خراب, sensores aparcamiento no funcionan, sensores reversa no funcionan, no pita al aparcar, حساسات الركن لا تعمل, رادار الرجوع معطل, الحساسات ما تشتغل
What this usually means
Check the free things first, because they are the commonest causes by a distance. Mud, ice and packed snow across the sensor faces stop them working entirely, which is why these faults appear in winter and clear at a car wash. Anything fitted in the sensing area — a towbar, a bike rack, a tow eye cover, a thick number plate surround — is detected exactly as designed and reported as a permanent obstruction.
Then ask whether the bumper has been painted or replaced. A sensor has to vibrate through its own face, and one extra coat of paint is enough to silence it. A bumper resprayed with the sensors left in place is a classic and entirely invisible cause.
The pattern tells you where to look. Constant beeping the moment reverse is selected means one sensor is reporting something permanently in front of it — and which corner it sounds for usually identifies which sensor. Nothing at all, on any sensor, points instead at the module, its supply or its wiring.
Remember what ultrasound is bad at, because it is not a fault. Soft surfaces, sloped bollards, thin posts and angled walls reflect the chirp away rather than back, so they can genuinely be missed — the system is an aid to looking, not a substitute for it. Heavy rain on the bumper produces false readings for the same reason.
And if nothing beeps but the display still shows obstacles, the sensors are fine — that is the sound path, which has its own entry.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Stopped working in winter, fine after a wash | Mud, ice or packed snow across the sensor faces | Clean each sensor face and retest. Free, and it is the most common cause. | No repair. |
| Constant beeping the moment reverse is selected | One sensor reporting something permanently in front of it — or something genuinely fitted there | Note which corner it sounds for. Check for a towbar, bike rack, tow eye cover or plate surround. | Remove the obstruction, or renew the sensor that is reporting falsely. |
| Stopped after the bumper was painted or replaced | Paint over the sensor face — a sensor must vibrate through its own surface | Inspect the faces closely. One extra coat is enough and it is entirely invisible. | Renew the affected sensors. Paint cannot be removed from the face without damaging it. |
| Nothing at all from any sensor | The module, its supply, or its wiring rather than the sensors | All sensors failing together rules out individual faces. Check the fuse and the module. | Repair the supply or the module. |
| Misses low walls, posts or sloped bollards | Not a fault — ultrasound reflects away from angled and thin surfaces | This is a limitation of the physics, not a failure. Test against a flat wall to confirm the system works. | No repair. The system is an aid to looking rather than a substitute. |
| Display shows obstacles but nothing beeps | The sound path rather than the sensors — they are still detecting | Watch the display while reversing. Detection without sound isolates it cleanly. | See the warning-chimes entry. Treat the car as having no parking aid meanwhile. |
-
Stopped working in winter, fine after a wash
- Likely cause
- Mud, ice or packed snow across the sensor faces
- How to confirm it
- Clean each sensor face and retest. Free, and it is the most common cause.
- What fixes it
- No repair.
-
Constant beeping the moment reverse is selected
- Likely cause
- One sensor reporting something permanently in front of it — or something genuinely fitted there
- How to confirm it
- Note which corner it sounds for. Check for a towbar, bike rack, tow eye cover or plate surround.
- What fixes it
- Remove the obstruction, or renew the sensor that is reporting falsely.
-
Stopped after the bumper was painted or replaced
- Likely cause
- Paint over the sensor face — a sensor must vibrate through its own surface
- How to confirm it
- Inspect the faces closely. One extra coat is enough and it is entirely invisible.
- What fixes it
- Renew the affected sensors. Paint cannot be removed from the face without damaging it.
-
Nothing at all from any sensor
- Likely cause
- The module, its supply, or its wiring rather than the sensors
- How to confirm it
- All sensors failing together rules out individual faces. Check the fuse and the module.
- What fixes it
- Repair the supply or the module.
-
Misses low walls, posts or sloped bollards
- Likely cause
- Not a fault — ultrasound reflects away from angled and thin surfaces
- How to confirm it
- This is a limitation of the physics, not a failure. Test against a flat wall to confirm the system works.
- What fixes it
- No repair. The system is an aid to looking rather than a substitute.
-
Display shows obstacles but nothing beeps
- Likely cause
- The sound path rather than the sensors — they are still detecting
- How to confirm it
- Watch the display while reversing. Detection without sound isolates it cleanly.
- What fixes it
- See the warning-chimes entry. Treat the car as having no parking aid meanwhile.
Codes that produce this symptom (4)
Listed with the codes that most typically present this way first — the likeliest place to start.
- U0159 Lost Communication With Parking Assist Control Module A Typical of this code Moderate
- U0243 Lost Communication With Parking Assist Control Module B Typical of this code Moderate
- U045A Invalid Data Received From Parking Assist Control Module A Typical of this code Low
- U0544 Invalid Data Received From Parking Assist Control Module B Typical of this code Moderate
Information, not instruction
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