Fleets are being warned that using engine remapping on their vehicles runs the risk of invalidating their warranty.

Several fleets have used remapping, which involves retuning the engine’s control unit, to increase fuel economy and reduce CO2 levels. They include BT Openreach and Homeserve.

However, Renault, Citroën, Peugeot and Vauxhall have joined Mercedes-Benz in saying that any faults that occur due to remapping will not be covered by warranty.

In addition, with vehicle emissions under ever closer scrutiny, the Department for Transport (DfT) has confirmed that vehicles with remapped engines are legal, but only if the retuning process does not have a negative impact on what comes out of the tailpipe.

A spokesman for the DfT said: “It is an offence to use a vehicle which has been modified so it does not comply to emissions standards was designed to meet.”

Steve Bridge, managing director of Mercedes-Benz Vans, said: “While modifications of this nature are well documented, our view remains that any such modification remains the responsibility of the entity carrying out the conversion. They should be subject to the same regulatory standards that manufacturers are obliged to meet.”

This includes European whole vehicle type approval.

A spokesman for Peugeot said: “We do not approve of remapping or any non-approved changes to our vehicles.

“We create vehicles with a specific set of ECU (digital) codes that are then homologated.

“Changing the codes could affect whether that vehicle still meets current homologation standards, which obviously if it doesn’t can affect safety or emissions.”

Renault is slightly more lenient, stating that engine remapping does not in itself automatically impact on the manufacturer’s warranty.

However, a spokesman added: “If an incident arises with the vehicle that has been directly or indirectly caused by the modification, the repair or rectification costs would not be our responsibility.”

Bridge questioned the impact of remapping on regulated emissions, against which vehicles are certified.

However, engine remapping company Viezu Technologies said its Blue Optimize tuning process does not increase the amount of NOx levels a vehicle emits.

It has remapped 24,000 vans for BT Openreach and 400 for Homeserve.

According to BT Fleet, the introduction of remapping delivers an average fuel saving of 15% and a 25% reduction in CO2 emissions. It also launched its own remapping service last year.

Homeserve’s use of the technology has not been without incident, however.

Linda Busby, managing director of Viezu, said: “A very limited number of vehicles, which have been through the Homeserve programme, have experienced an in-service issue and we are currently working together to investigate this fully through our normal independent warranty process which is available to all of our remapping clients.”

A spokesperson for Homeserve told Fleet News it was “an ongoing matter” but declined to comment further.

Viezu believes it is wrong for manufacturers to void warranty cover if a vehicle has been remapped.

Paul Busby, Viezu chief executive, said: “Customers should have the right to make changes to a vehicle with a clear understanding that if there is a component failure, this is fully investigated by the manufacturer on a case-by case basis, before making a warranty decision.

“Viezu is committed to this approach and will always support such investigations.”

However, Busby said fleets should be wary of how other companies operate and encouraged them to carry out due diligence when looking at remapping vehicles to fully understand the impact it will have on emissions.

He explained: “It’s important that any fleet operator considering remapping or other tuning devices as a strategy to reduce their fuel costs perform their due diligence with a great deal of care and attention, making sure that the tuning company can deliver on its promises and doesn’t inadvertently make any emissions problem even worse.”

European Union emission regulations for new light duty vehicles (passenger cars and light commercial vehicles) state that Euro 6 diesel engines must not emit more than 0.08g/km NOx.

This has been reduced progressively since Euro 1 was introduced in 1992, when the limit was 0.97g/km, this calculates to a 92% reduction in the last 23 years.

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