Diagnostic Instructions

DTC Descriptors

DTC P0090: Fuel Pressure Regulator Control Circuit

DTC P0091: Fuel Pressure Regulator Solenoid 1 Control Circuit Low Voltage

DTC P0092: Fuel Pressure Regulator Solenoid 1 Control Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
FRP regulator High	P0091	P0090	--	--
FRP regulator Low	P0091	P0090	P0092	--

Circuit/System Description

High pressure fuel is regulated by the fuel rail pressure (FRP) regulator, which is a part of the high pressure fuel pump. The FRP regulator is a solenoid valve. The ECM provides battery voltage on the FRP regulator high circuit and ground on the FRP regulator low circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled. When activated, the FRP regulator low circuit driver connects the low circuit to ground and the FRP regulator high circuit driver pulse-width modulates (PWM) the high circuit. The ECM monitors the voltage on the circuits to detect a failure.

Conditions for Running the DTC

Conditions for Setting the DTC

P0090

P0091

P0092

Action Taken When the DTC Sets

Conditions for Clearing the DTC

DTCs P0090, P0091, and P0092 are Type A DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Engine idling, observe the Actual Fuel Rail Pressure parameter with a scan tool. The pressure should be approximately 3.5-5.5 Mpa (508-798 psi).
2. Command an increase and decrease in fuel rail pressure with a scan tool. Observe the scan tool Actual Fuel Rail Pressure parameter. The Actual Fuel Rail Pressure should increase or decrease with each command.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, raise the vehicle.
2. Disconnect the harness connector at the high pressure fuel pump.
3. Engine running, verify that a test lamp flashes between the FRP regulator low circuit terminal 1 and B+.

⇒	If the test lamp is always ON, test the FRP regulator low circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If the test lamp is always OFF, test the FRP regulator low circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Ignition ON, verify that a test lamp illuminates between the FRP regulator high circuit terminal 2 and ground.

⇒	If the test lamp does not illuminate, test the FRP regulator high circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the high pressure fuel pump.

Component Testing

Static Test

1. Ignition OFF, disconnect the harness connector at the high pressure fuel pump.

Note: The DMM and test leads must be calibrated to 0 Ω in order to prevent misdiagnosis.

2. Test for 0.49 Ω plus/minus 0.023 Ω of resistance at 20°C (68°F) between FRP regulator low circuit terminal 1 and FRP regulator hi circuit terminal 2.

⇒	If not within the specified range, replace the high pressure fuel pump.

3. Measure the resistance between each terminal and the high pressure fuel pump housing. The DMM should display O.L.

⇒	If not the specified value, replace the high pressure fuel pump.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.