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Discussion Starter #1
Got a call the other day that the Malibu displayed the CEL/Reduced Engine Power.
Pulled the codes and got P228C and P00C6.
Started by replacing the Fuel Pressure Switch (ACDELCO) on the front of the tank. Cleared the codes, drove the vehicle and codes came back. Replaced the Mechanical High Pressure Fuel Pump (ACDELCO) on the Engine itself. Started the vehicle up and the same codes reappeared. Scan tool stated 43.5psi fuel pressure on the freeze frame data. Am I looking to have to replace the in tank fuel pump assembly?
 

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Year and engine size would help. If you have a 2.5 see below.
DTC Descriptors

DTC P0089
Fuel Pressure Regulator Performance

DTC P00C6
Fuel Rail Pressure Low During Engine Cranking

DTC P228C
Fuel Pressure Regulator Control Performance - Low Pressure

DTC P228D
Fuel Pressure Regulator Control Performance - High Pressure

Circuit/System Description

The high fuel pressure necessary for direct injection is supplied by the high pressure fuel pump. The high pressure fuel pump is mounted on the rear of the engine and is driven by a three-lobe cam on the intake camshaft. This high pressure fuel pump also regulates the fuel pressure using an actuator in the form of an internal solenoid-controlled valve. In order to keep the engine running efficiently under all operating conditions, the engine control module (ECM) requests pressure ranging from 2 to 15 MPa (290 to 2,176 PSI), depending on engine speed and load. Output drivers in the ECM provide the pump control circuit with a 12 V pulse-width modulated (PWM) signal, which regulates fuel pressure by closing and opening the control valve at specific times during pump strokes. This effectively regulates the portion of each pump stroke that is delivered to the fuel rail. When the control solenoid is NOT powered, the pump operates at minimum flow rate. In the event of pump control failure, the high pressure system is protected by a relief valve in the pump that prevents the pressure from exceeding 17.5 MPa (2,538 PSI).

The fuel rail pressure sensor provides the feedback necessary to the ECM to control the high pressure fuel pump and the fuel injectors. This sensor is diagnosed separately from the fuel pressure control system.

The ECM monitors the fuel rail pressure sensor and the high pressure fuel pump actuator to determine if the commanded and actual pressures are within a predetermined range during engine cranking and at all times while the engine is running. The ECM also monitors the fuel pump actuator to make sure it is operating within expected limits.
 
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