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TSB 12-7-7 (and previously TSBs 11-4-22 and 11-4-15) deals with the code P0088. Per the TSB, if the P0088 is the only code present, if states to reprogram the Powertrain Control Module (PCM) to the latest calibration. The previous TSBs stated to replace the high pressure fuel pump which may not need to be done. If reprogramming the PCM makes no difference, check the circuits going to the fuel Volume Control Valve (VCV) and fuel Pressure Control Valve (PCV) solenoids in the high pressure fuel pump. First access connector C1926 (this is a square 4 terminal connector) located at the rear of the Right Hand (RH) valve cover. The wires for the VCV are pin 2, Yellow (YE) wire and pin 4, Green/White (GN/WH) wire. The wires for the PCV are pin 1 Yellow/Violet (YE/VT) wire and pin 3, GN/WH wire. Put a voltmeter between each pair of wires and run the meters inside the truck to monitor while driving. Also monitor the VCV and PCV command readings on the scanner when driving. As the duty cycle increases on the scanner, the voltage across the wires for each solenoid should increase and as the duty cycle decreases, the voltage should decrease. If the voltage ever goes up when the command is going down, indicating that the control circuit for either solenoid could be shorting to ground, the harness for the solenoids will need to be accessed to check for chafed or shorted wires. Repair the wires as needed. Also check the Fuel Rail Pressure (FRP) Sensor voltage reading with key on. The sensor should read roughly 0.49 V with no pressure in the system. While monitoring voltage, wiggle the wiring at the Right Hand (RH) valve cover looking for the voltage to become erratic, indicating a possible connection problem that could skew the FRP Sensor reading. If the voltages on the FRP Sensor and control solenoids check OK and follow the command on the scanner when the code sets, then suspect a mechanical fault with either the VCV or PCV solenoid in the high pressure fuel pump and follow the TSB for replacing the pump as needed.
Here is the TSB that addresses it:
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