Sensor problems

Can you tell me if motor factors’ sensors are inferior to genuine main dealer parts? Also, I was told that the 02 sensors on my car could have failed due to using cheap supermarket petrol. Is there any truth in this?

Finally, if my engine management light is illuminated, does this mean an automatic MOT failure? Michelle Osborne-morgan

As there is such a broad range of sensors on the market, and as I have come across non-genuine sensors that have failed after a short time, I would advise that Oe-quality sensors should be used whenever possible. This does not necessarily mean using a main dealer part, as sensors from many reputable manufacturers can be bought from a motor factors.

An 02 sensor can fail if the silicone content of the fuel is too high. Silicone is used as an antifoaming agent. In 2007, an incident occurred where tankers used to supply fuel to supermarkets had not been correctly cleaned, leading to a high content of silicone in the fuel, which did lead to a number of 02 sensors being damaged. This is not a reflection on the standard of supermarket fuel, but rather a problem with contamination of the fuel on the journey to the filling station. The quality of petrol and diesel is governed by a European standard and applies to all fuel. Supermarket fuel is sourced from all the major producers and is controlled to the same standards as branded fuels. Supermarkets also sell premium fuels and, like branded premium fuels, these should also offer better performance and lower fuel consumption.

In itself, the engine management light being on is not a failure item for the MOT. If it is illuminated because the 02 sensor has failed and the emissions are not within the limits set by the MOT, then the vehicle will fail on the emissions, not the light.