I've been attempting this problem regarding the usage of Thévenin's Theorem to find the value of Io. I am able to get the correct Thevenin Resistance, however attempting to find the Thevenin Voltage has been confusing me. When breaking the circuit at the 4kOhm resistor I tried to do a kVl loop around the bottom left square containing the 5V source and the open voltage from opening the resistor and got a value of 5 which is incorrect. I'm confused as to why it is incorrect and am wondering if it is because there is a voltage attributed to the 2mA independent source which I am not considering. I have attached the problem, any guidance would be greatly appreciated.