Possible causes

– Faulty Power Steering Pressure Sensor
– Power Steering Pressure Sensor harness is open or shorted
– Power Steering Pressure Sensor circuit poor electrical connection

When is the code detected?

An out of range voltage from the Power Steering Pressure Sensor is sent to Engine Control Module (ECM).

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Power steering inoperative

P0551 MITSUBISHI Description

Power steering pressure (PSP) sensor is installed to the power steering high-pressure tube and detects a power steering load. This sensor is a potentiometer which transforms the power steering load into output voltage, and emits the voltage signal to the Engine Control Module (ECM). The ECM controls the electric throttle control actuator and adjusts the throttle valve opening angle to increase the engine speed and adjusts the idle speed for the increased load.