Carbon cleaning is not as such a fix, its original purpose is cleaning as a preventative measure as carbon build-up is the root cause of 85% of the failure of components. If the component is simply clogged with carbon using not just our basic Hydrogen cleaning system but also our proprietary chemicals (that our competitors do not have access to) it is often possible to restore the operation of some components such as an EGR valve. However, if the component has failed then of course cleaning cannot fix something that has already failed. If you have an engine management system fault or a component diagnosis we recommend speaking to your local technician to discuss success ratios and options.