I believe the DPFE sensor is at the back of the 5.0 L by the throttle body
On the 4.0 L - OHV - engine , its on the drivers side of the upper " plastic " intake manifold
I'm not a mechanic / technician but I had the DPFE sensor changed on my Ford Explorer . As far as I know it is used to control the amount the Exhaust Gas Recirculation ( EGR ) valve opens
On my 1995 Ford Explorer with the 4.0 liter OHV engine the DPFE sensor ( differential / or delta pressure feedback Egr sensor ) is located on the upper intake manifold on the drivers side of the engine
you needs a dpfe sensor
On the right rear of the engine by the throttle body.
The delta pressure feed back egr sensor is located on the intake manifold. It is a metallic rectangular thingy with vacuum lines and a connector on it.
The DPFE is located on the left side of the upper intake manifold across from the battery. It has two rubber hoses on the bottom with a wire connector attached.
Ford is the only American car company that uses a DPFE sensor. GM dpfe sensor are built into the EGR.
On a 2000 Ford Explorer XLS, the DPFE (Differential Pressure Feedback EGR) hoses are typically located near the EGR valve, which is mounted on the intake manifold. The DPFE sensor itself is usually situated on the firewall side of the engine bay, connected to the EGR system. The hoses run from the DPFE sensor to the EGR passage, enabling it to monitor pressure differences. For exact locations, consulting the vehicle's service manual or a repair guide is recommended.
I dont believe the Impala 2003 uses a DPFE sensor as part of there Emissions system.
P1401 is DPFE sensor circuit high, check out this tutorial to replace the sensor on your Ford