The FRP sensor is like a diaphragm which calculates the pressure changes between the atmospheric pressure and the fuel rail, and sends a signal to the PCM (Powertrain Control Module) that corresponds to the reading of the pressure of the rail gas.
The Power Train Control Module (PCM) uses this signal to control the injection time and the correct impulse amplitude for the required fuel supply under speed and load conditions.
With the fuel volume regulator, the Fuel Rail Pressure Sensor (FRP) establishes a closed-loop fuel pressure control system. In the event that this sensor has an electrical fault, the result is that the fuel injection pump is deactivated.
A code P0191 may have one or more of the following problems:
Fuel pressure can be very high or very low.
The FRP (Fuel Rail Pressure) sensor may be defective.
An excessive resistance of the circuit.
Low fuel level.
Possible solutions of the DTC code P0191 Generic
To solve the diagnostic code P0191 OBD II you must first make sure you do not have a code related to the fuel pressure pump. If so, diagnose that code first, since it may be the cause of the P0191 code. This occurs in particular when there are startup problems.
Otherwise locate the Fuel Rail Pressure Sensor (FRP) and visually check the cables and their connectors, make sure they are not burned or have any friction. Change if necessary.
Examine the terminals inside the connectors, check for burns or have a green color compared to the usual metallic color. If you have any of these characteristics, you can use an electrical contact cleaner or a solution that has 91% alcohol and a brush to clean the terminals, or you can replace them.
Check that the vacuum hose that is connected to the intake manifold is not leaking. Change if necessary.
With your preference scanner, delete the P0191 code and see if this code reappears. If it does, you can change the FRP (Fuel Rail Pressure) sensor and check the connections of the Power Train Control Module (PCM).