P0091

DTC P0091

Circuit Description
The suction control valve (SCV) is installed to the fuel supply pump and controls the suction fuel quantity into the fuel rail. The SCV is fully opened in the normal state and larger drive current results in smaller opening. The engine control module (ECM) calculates desired fuel rail pressure and fuel flow rate and it compares the calculated desired fuel rail pressure to the actual value to determine the SCV position. When the actual fuel rail pressure is higher than the desired value, the SCV is closed to decease the flow rate. If the ECM detects an excessively low SCV solenoid drive current, this DTC will set.

Condition for Running the DTC
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.
- The fuel supply pump control is normal.
- The SCV operating duty cycle is between 20-50%.
- The deviation of SCV operating duty cycle is less than 10%.

Condition for Setting the DTC
- The SCV operating current is less than 400 mA.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
- The ECM limits fuel rail pressure within 11600 psi (80 MPa).
- The ECM limits accelerator control range to idle.
- The ECM closes the EGR valve and holds to close position.
- The ECM inhibits the cruise control.
- The ECM inhibits the PTO control.

Condition for Clearing the DTC
- A current DTC clears when the ignition is turned OFF.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
If an intermittent condition is suspected, the following may cause an intermittent:
- Poor connections.
- Misrouted harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.

Check for the following conditions:
- Poor connection at ECM: Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness for damage. If the harness appears to be OK, observe the "Actual Suction Control Valve Control Current" display on the scan tool while moving connectors and wiring harness. A change in the display will indicate the location of the fault.

Test Description
The numbers below refers to the step number on the diagnostic table.
8. If the SCV low control circuits between the ECM and the SCV are short to ground, this DTC may not stored. This condition will cause engine stall or no engine start.

DTC P0091

Schematic Reference: Engine Controls Schematics

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