Mechatronic unit replacement

The consumer’s issue:

“I purchased a used ’13-plate SUV from a dealership in August 2016. At the time, it had approximately 7,000 miles on the clock. In February 2018, just under a year and a half after buying the car, the mechatronic transmission control unit failed, and it cost me £1,200 to repair the issue. But, just 13 days later, the car broke down again and it was recovered back to the dealership. They informed me that the entire gearbox needed to be replaced at a cost of £3,700. I wasn’t happy with this, so they offered to use the car as a part-exchange for another one.

I’d lost confidence in the dealership’s ability to repair the vehicle, so I agreed to this. However, the dealership deducted £3,700 from the value of the part-exchange, which was equivalent to what they said it would cost to repair the car. I’m unhappy with this, because the vehicle was under five years old with less than 24,000 miles on the clock when the mechatronic unit and gearbox failed. Therefore, I don’t believe the car was of satisfactory quality when it was sold to me, and I feel the second failure of the transmission was a direct result of the dealership’s previous repair to the control unit.

To resolve this dispute, I am looking for the business to refund the money they charged me for the mechatronic unit replacement, and the deduction they applied on the part exchange, as the repairs should have been completed for free and I should not be penalised for the gearbox’s eventual failure.”

The accredited business’ response:

  • In February 2018, the consumer complained that the gears couldn’t be selected, and the transmission alarm was sounding.
  • We investigated the issue in accordance with the manufacturer’s diagnostic procedure and determined that the mechatronic control unit required replacement. The consumer authorised the repair.
  • Following this, we found further problems with the gearbox and we recommended that it should be replaced.
  • The car was second-hand when it was sold, and the consumer had covered 16,000 miles during the 18 months they had possession of it with no concerns. Therefore, the vehicle was of satisfactory quality at the point of sale.
  • The mechatronic unit repair we carried out in February 2018 did not fail, rather we found further problems with the gearbox that hadn’t been addressed by the mechatronic unit replacement.
  • We were not asked to investigate the cause of the fault, and we believe that the gearbox issues were related to the initial failure of the mechatronic unit and the continued use of the transmission while the mechatronic unit was deteriorating.
  • In conclusion, we don’t believe that the gearbox failure was linked to our workmanship, or that the car was not of satisfactory quality when sold. We also provided a favourable deal for the consumer to trade in the car.

The adjudication outcome:

  • The Motor Ombudsman adjudicator reviewed the evidence, but found that it was insufficient to show why the mechatronic unit had failed.
  • She also said there was no information to show why the entire gearbox had stopped working following the mechatronic unit replacement.
  • The adjudicator said that, when looking at the age and mileage of the car, it seemed unreasonable for this type of component to fail so soon.
  • Therefore, she said that it was more likely than not that the car hadn’t been of satisfactory quality at the point of sale.
  • She upheld the consumer’s complaint and recommended that the dealership refunded the cost of the mechatronic unit replacement, and the deduction in the value of the car when it was traded in.
  • The dealership disagreed with the adjudicator’s assessment and requested a final decision from the ombudsman.

The ombudsman’s final decision:

  • The ombudsman reviewed the information provided and noted there were two aspects to the complaint. Firstly, she said there was a dispute regarding the quality of the car which was a sales complaint. The second issue was about the dealership’s quality of repairs and workmanship.

First issue: quality of the car


  • The ombudsman said that, under the Consumer Rights Act 2015, the dealership must supply a car that is of satisfactory quality, given the age, mileage and price paid for the car.
  • She explained that, if a fault is found to have been present or developing with the car and its components at the time of sale, then the consumer is entitled to either a repair, a replacement, a price reduction or a rejection of the vehicle.
  • The ombudsman considered the dealership’s comments, but said that the mechatronic control unit is a computerised module found within the gearbox itself which controls the automatic transmission in a vehicle. Also, it is not a serviceable component.
  • She acknowledged the consumer had covered around 16,000 miles with the car during 17 months of ownership, before a fault arose.
  • She accepted that problems can develop for various reasons, but said that service and maintenance wasn’t the cause of the failure on this occasion. She also considered that it was highly unlikely the gearbox failure was due to wear and tear, seeing as the car was only four and a half years old and had completed 23,000 miles at this point.
  • She also noted from the repair invoices that, in February 2017, within six months of the consumer buying the car, the mechatronic unit had been re-programmed, thereby indicating that there was a previous issue with it prior to its eventual failure, of which the dealership ought to have been aware.
  • She said it was more likely than not that the issues in February 2017 were linked to the eventual failure in February 2018, and that the fault with the mechatronic unit was present and / or developing when the car was sold.
  • The ombudsman highlighted the fact that satisfactory quality also included durability. Taking into account the price paid for the car, its age and mileage, and the fact that there was no evidence to suggest that the mechatronic unit had failed due to wear and tear, foul play or some other external influence, she concluded that the gearbox and mechatronic unit hadn’t been durable enough and had been inherently faulty at the time of sale. As a result, the ombudsman explained that the replacement of the mechatronic unit should have been completed at no cost to the consumer.
  • The ombudsman upheld this aspect of the complaint and directed the dealership to refund the £1,200 the consumer had paid for this work.

Second issue: service and repair


  • The ombudsman went on to state that a dealership has a legal obligation to exercise reasonable care and skill when diagnosing and carrying out repairs on a car. If a business falls short of this, then they must put things right.
  • She noted that, 13 days after the mechatronic unit replacement, the car broke down and the dealership concluded that the entire gearbox needed changing.
  • She said that, although the dealership had said the gearbox failure wasn’t a result of their previous repair, and that that there had been additional problems with the transmission, they had not in fact stated what these other additional problems were.
  • The ombudsman explained that the dealership also hadn’t provided any evidence to show exactly what checks they carried out for them to conclude that the entire gearbox needed replacing.
  • She found that the dealership had been inconsistent in their responses, as they’d said that the gearbox had failed due to continued use of it, yet they’d equally stated that they hadn’t investigated the actual cause of problem.
  • The ombudsman went on to say that the consumer had seen no other alternative but to trade in the car with a substantial amount being deducted so as to avoid any potential future repair costs. The customer had also made their dissatisfaction clear prior to the trade-in taking place.
  • The ombudsman decided that, due to the lack of evidence, inconsistent information and the fact the failure had occurred 13 days after a substantial repair to the gearbox had already been carried out, the onus was on the business to prove that the subsequent failure wasn’t a result of their workmanship.
  • She concluded that the dealership hadn’t been able to supply enough evidence to discharge their liability on this occasion and upheld the complaint in the consumer’s favour. She therefore directed the dealership to refund the £3,700 that had been deducted from the value of the car that had been part exchanged.


  • Both parties agreed with the final decision, and the dealership refunded the consumer £4,900 in total, as per the ombudsman’s final decision.