Can anyone explain this 'checking the earth' process, preferably specific to the vehicles that Rafa & I have, leaf cab chassis. I have lived with the same problem. If it's just a matter of the main earth to chassis connections, that' not the problem, at least not in my case. I have added extra earth connections. Dropping the fuel tank to get at the connections on top of it seems like a big drama. Is this what is required? It is so frustrating to be able to see all those connections on top of the tank, but just out of reach.
Really though I think it is more likely a dry solder joint in the pcb behind the dash, as someone else has described previously, which is nightmare stuff for me. Not a job I want to attempt myself, but fearful if I take it to Nissan or an auto electrician it could take a long time (& LOTS of cash) to find the cause. Rafa does your sub tank misread too? Mine does, & occasionally the speedo needle, but the problems are intermittent & unpredictable. Much of the time it works ok, but I cannot trust it. Shits me.

Cuppa