British drivers are putting themselves at risk of major bills this winter due to preventable vehicle breakdowns.
That’s the finding of new research into cold-weather faults, which reveals the three most common issues identified could cost drivers a total of £2,481.
The data showed that diesel engine glow plugs, auxiliary coolant pumps and air quality sensors are the components most likely to go wrong during the coldest period of the year.
Although replacing a blown fuse could be the simplest (and cheapest) root cause for such failures, having to replace an entire glow plug control unit could top £1,200.
This figure exceeds the average monthly rent paid by UK households, coming at a time when finances are already stretched after the Christmas period.
Top car breakdown causes identified
Automotive diagnostics platform Carly uncovered the new data by analysing more than 2.4 million diagnostic sessions between October and December 2025.
The company’s plug-in system uncovered the three most common winter car failures, along with the probability of each one generating a detectable fault code.
Glow plug issues only occur in diesel vehicles, and were linked to a 60 percent probability in Carly’s analysis. Replacing an individual glow plug might cost between £618 and £835, while a simple fuse could be as little as £56 to sort.
From Carly’s dataset, auxiliary coolant pump failure had a 65 percent probability of causing an issue. Having to replace the pump means a bill of between £570 and £820, with a defective cable costing from £116 to £160.
The most frequent breakdown cause was air quality sensors, with a 78 percent occurrence. Having to fit a new sensor costs between £281 and £395 on average.
‘Better visibility of vehicle health’
The Carly device connects to a vehicle’s on-board diagnostics (OBD) port, allowing drivers to detect and understand recorded fault codes.
This could potentially mean spotting an issue before it causes greater damage, or even allow drivers to budget for repairs.
Commenting on the findings, Dali Ati, head of internationalisation at Carly, said: “Winter breakdowns remain a significant and costly issue for UK drivers.
“Our data shows that some of the most common faults reported during colder months – particularly bad for owners of diesel cars considering the cost range and likelihood of glow plug-related failures – can also be among the most expensive to fix.”
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