Circuit/System Testing

P0087

1. If DTC P0090, P0168 or P0191 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
IMPORTANT: Ensure that the transmission is in Park or Neutral with the parking brake set.
2. Attempt to start the engine.
   • If the engine does not start, refer to Engine Cranks but Does Not Run .
3. Install the J 44638  to the fuel rail service port and slowly increase the engine speed until reaching wide open throttle (WOT). See Special Tools .
   • If more than 5 inches of vacuum was present during engine speed increase, replace the fuel filter and inspect for fuel system restrictions.
4. Command the fuel pressure control to 180 MPa (23,206 psi) with a scan tool. Observe the Actual Fuel Rail Pressure parameter. The actual fuel pressure should be the same as the commanded pressure.
   • If the Actual Fuel Rail Pressure is less than 145 MPa (21,030 psi), refer to Fuel System Diagnosis - High Pressure Side .
IMPORTANT: If the fuel temperature is near 121°C (250°F) during the duplication of the complaint, or in the Failure Records for this DTC, inspect for a restriction in the fuel cooler air flow or the fuel heater always ON. Refer to Fuel Heater Always On .
5. Operate the vehicle within the conditions for which the customer complaint occurs while observing the J 44638  . See Special Tools . You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records.
   • If the vacuum was more than 12 inches Hg of vacuum at any time in the operating range, inspect for a restriction in the fuel supply lines.

• If the vacuum was always less than 12 inches Hg of vacuum, refer to Diagnostic Aids .

P0088

1. Start the engine and operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
2. Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 30 MPa (4,352 psi) with the engine idling at operating temperature.
3. Change the fuel pressure with a scan tool, incrementing through the entire fuel pressure range. The fuel pressure should increment and stabilize through the entire fuel pressure range, with actual and desired fuel pressure within 2 MPa (290 psi) of each other.
   • If the pressure difference between the actual and desired pressure are more than 2 MPa (290 psi), replace the fuel pressure regulator.
4. Test the fuel pressure regulator (FPR) solenoid control circuit and the FPR solenoid supply voltage circuit for high resistance.
   • If all circuits test normal, replace the ECM.