NISSAN FAN said:
have you all seen the new mot failures list ?? ,as of next yeartuning box's = fail </font>
As far as diesel engines go, all they do is raise the fuel rail pressure. They fit in between the rail sensor and the original wiring loom and kid the ECU that the pressure is lower than it actually is, thus raising the actual pressure to a point that can be adjusted by a wheel or jumpers in the 'box'.
Yes, they will be a fail item in the new UK MOT. These boxes are so easily and quickly installed that it only takes a few moments to whip them off and re-fit after the MOT.
They generally work better on some engines than others.
I would prefer to have a proper ECU re-map than a tuning box. However some of the latest ECU's fitted have anti-remap protection.