The Truth About Diesel Tuning Boxes

Diesel tuning boxes are supplied by many different types of company, some with just profit in mind and a very small number who think they are helping people improve the performance of their vehicles or save money by increasing miles per gallon/litre

Are Tuning Boxes Safe?

The truth is that while a few of these products work to some extent, the effect that they have on your engine can be mind boggling. Unfortunately as they work by changing the data that your engine ECU actually sees (it changes the data from things like MAF Sensor, MAP Sensor, Fuel Rail Pressure Sensor, etc.) it cant actually see what effect it is having on your engine and if that is safe or not.


We regularly get vehicles come to our workshop that are suffering with excess smoke, poor fuel economy, blocked DPF Filter's etc. Often these symptoms are caused by tuning boxes, sometimes where the owners have no knowledge that they have been fitted! Simply removing the Tuning Boxes and resetting the calibrations in the Engine ECU resolve the problems completely and the owners go away happy without noticing any difference in performance and see huge increases in MPG.

Tuning Box Failure Can Be Difficult to Diagnose.

We had a Range Rover L322 TD6 arrive at the workshop recently with symptoms that suggested serious fuelling issues, heavy smoking, jerking at various engine/vehicle speed combinations. The vehicle was pretty much undrivable due to the jerking and heavy smoking. This vehicle had been inspected at a number of Land Rover Dealers and independent specialists before coming to us. There were no fault codes stored and looking at all the live data showed all readings within manufacturers specifications. We were told that the vehicle definitely had no tuning boxes fitted and the car had not been remapped. It is our practise to check sensor readings at the Engine ECU connectors and compare the information with the data that the ECU is seeing. It was at this point that we noticed that the wiring harness appeared to have been re-wrapped with loom tape, we removed the loom tape and discovered a well hidden Tuning Box underneath the rest of the control units etc. in the box on the offside of the engine bay. We disconnected the tuning box and the engine was transformed, after resetting the adaptions in the engine and gearbox/transfer box the vehicle drove just as it should. Fortunately there appears to be no further damage caused by the tuning box, however this did highlight an issue that we hadnt thought of before, tuning boxes, unlike remaps, can fail due to hardware problems and cause problems that are not easy to determine normally. The customer had already wasted almost £1000.00 on sensors that were not within specifications and labour elsewhere.