The alarm you’re seeing is the car’s way of telling you that it’s been working hard and needs attention sooner rather than later. The on-board computer will be monitoring all sorts of parameters including the engine oil level and condition and the state of the air-filter element. Either of those things (and a large number of others) could be the trigger for the alarm you’re seeing. But it could also be due to the transmission being heated to a point where the computer says enough, or even an actual problem somewhere in the driveline such as a low coolant level.

The best thing to do is have the vehicle serviced as per its own request. The workshop might be able to tell you the cause of the alarm, but either way, maintenance is due. Towing a caravan places a lot of extra stress on the engine and transmission, while hot and dusty conditions also take their mechanical toll.

Okay, first question: Did the sensor damage happen before or after the failure of the alert? If it’s the former, it’s a fair bet the crunch has broken the sensor in question and led to the whole inter-linked system failing.

If the problem happened before the bump (and caused the knock because it didn’t warn you of the looming barrier) then you need to investigate further. An auto electrician should be able to test the system and its circuits and tell you what the cause of the problem is. It could be anything from the wiring to a blown fuse to the sensors themselves having failed. Living on the very edge of the vehicle, these sensors have a pretty hard life with every tap and bump to the bumper potentially damaging them or their circuitry.

It will be an ongoing issue when towing. Drive to the conditions, don’t try and tow up hills in overdrive gears when the engine will work harder, and if you’re worried have a heavy-duty transmission oil cooler fitted.