P1186 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P1186 – Fuel Pressure Monitoring-Minimum Pressure at Engine Speed Too Low

 

P1186 Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

P1186 Possible Causes

 

Faulty Fuel pressure regulator valve (Stuck Open),Faulty Rail pressure sensor,Rail pressure sensor harness is open or shorted,Rail pressure sensor circuit poor electrical connection

 

P1186 Description

 

As inputted rail pressure sensor signal, Engine Control Module (ECM) of Common rail diesel engine controls Fuel pressure regulator valve(integrated with high press. pump) in order to maintain optimum rail pressure according to current engine rpm and load. However when the problem that leads rail pressure to out of target value intended by ECM occurs due to mechanical or electronical reason, ECM shuts engine down and sets Diagnostic Trouble Code (DTC) by limiting fuel (stops injector operation) in order to prevent engine from being controlled abnormally. “rail pressure monitoring error” is the DTC which diagnose 1).supplying state of low pressure fuel and 2).mechanical operating conditions of high pressure pump and 3) indirectly based on RPS output voltage and RPS duty. thus, repair relevant to this DTC requires mechanics the total understand of fuel system.