position sensor (transducers)
These are all potentiometers
All engine sesnors. ie TPS, MAP, O2 sensors, EGR, etc.......
All sensors, air pump, and EGR
This code indicates a problem with the EGR valve's pintle position. The EGR Valve's pintle could just be stuck in which case the problem could be fixed by cleaning the EGR valve. If the EGR valve is electronically controlled or cleaning the valve does not fix the problem, you will most likely have to replace the EGR Valve. Keep in mind that the EGR valve relies on inputs from other sensors to determine the pintle position. If one of these other sensors is not operating correctly, it could be giving you a false P1406 error code.
check that the vacuum hose is not clogged up
The P1406 trouble code typically relates to issues with the EGR (Exhaust Gas Recirculation) system, specifically indicating a problem with the EGR position sensor. Other sensors that could potentially contribute to this code include the throttle position sensor (TPS), which affects the EGR operation, and the intake air temperature (IAT) sensor, which can influence engine performance and emissions. Additionally, issues with the vehicle's mass airflow (MAF) sensor could impact the EGR system's functionality. Checking these sensors and their connections may help in diagnosing the underlying issue.
the 02 sensor on my 1994 4.9 6 cyl is located just pass the first converter in the exhaust pipe and the egr is to the right of the air tubes coming from the air box on the intake other sensors depend on which ones as to location
According to Alldata the 4.0L engine is not equipped with an EGR Valve. You don't have one on the 4.0
Have the system checked for codes. That will lead you to the problem.
Check the plug to the EGR sensors hasn't come loose or a wire broken to it.
type of sensors used in aeroplanes
Those are thermoswitches. They open and close vacuum supply to the egr valve and the distributor advance.