It's called the oil pressure relief valve, people tend to put a 1mm washer in and it gives a higher reading, what gauge have you got in at the moment? 1 bar is 14 psi, believe this or not toyota recommend no lower then 7 psi, which is abit low if you ask me, on first start up when cold is it only going to 1.4 bar? If you got one of them dodgy eBay cheap gauges in, that would be a good start to change that.