Sensor for exhaust valve?

There is no sensor. The thermocouple temperature at the bypass valve is read by the engine ECU to calculate the air temperature after the valve and infer what state the valve is in versus what state the valve should be in.

You have to reprogram the ECU to disable that function. However, there are opinions that wiring the valve always open lead to engine problems.

 

Not necessarily.

If the computer thinks the valve shoud be closed (at 2000 rpm) and it reads a temperature of 500 degrees as when the valve is wired open (like yours), it thinks the valve is bad and sets a CEL.

If it thinks the valve should be open (at 5000 rpm) and it sees a temperature of 100 degrees (as when you relocate the thermocouple), it thinks the sensor or the valve is bad and sets a CEL.

 

So, what you need to figure out is how to fool the ECU into thinking hte valve is closed when it is in fact open. You do this by using the electrical signal used to open the pneumatic valve that in turn opens the exhaust valve, and using this signal to create a voltage (resistor divider) and route it to the ECU. The ECU, then sees a low temperature when it thinks the valve is open and a higher temp when it thinks the valve should be open.

The only question left is at what voltages does the ECU think one thing versus the other. The rest is first year EE.