For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### 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
--- | --- | --- | --- | ---
High Pressure Fuel Pump Actuator High Control | P0091 | P0090 | -- | --
High Pressure Fuel Pump Actuator Low Control | -- | P0090 | P0092 | --

### Circuit/System Description

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

### Conditions for Running the DTC

• | The ignition 1 signal parameter is between 6-18.1 volts.

• | The DTCs run continuously within the enabling condition.

### Conditions for Setting the DTC

#### P0090

• | The high pressure fuel pump actuator voltage is between 1-4.5 volts with the actuator commanded OFF.

• | The DTC sets when the above condition is present for more than 4 seconds.

#### P0091

• | The high pressure fuel pump actuator voltage is less than 2.7 volts with the actuator commanded OFF.

• | The DTC sets when the above condition is present for more than 4 seconds.

#### P0092

• | The high pressure fuel pump actuator voltage is greater than 4.5 volts with the actuator commanded ON.

• | The DTC sets when the above condition is present for more than 4 seconds.

### Action Taken When the DTC Sets

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

• | A message center or an indicator displays Reduced Engine Power.

### 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### 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 pressure with a scan tool. Observe the scan tool Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure parameters. The Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure should closely match in all the commanded states.
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, disconnect the harness connector at the high pressure fuel pump.
2. Engine running, verify that a test lamp flashes between the high pressure fuel pump actuator low control circuit terminal 1 and B+.

⇒ | If the test lamp is always ON, test the high pressure fuel pump actuator low control circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒ | If the test lamp is always OFF, test the high pressure fuel pump actuator low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify that a test lamp illuminates between the high pressure fuel pump actuator high control circuit terminal 2 and ground.

⇒ | If the test lamp does not illuminate, test the high pressure fuel pump actuator high control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

4. 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.
2. Test for 0.49 ohm plus/minus 0.023 ohm at 20°C (68°F) between low control circuit terminal 1 and high control circuit terminal 2.

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

3. Test for infinite resistance between each terminal and the high pressure fuel pump housing/case.

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

#### Dynamic Test

Engine idling, command the Fuel Pressure Control to Increase with a scan tool. The Actual Fuel Rail Pressure should increase with each command.

⇒ | If the Actual Fuel Rail Pressure does not increase with each command, replace the high pressure fuel pump.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Control Module References for ECM replacement, setup, and programming

• | High Pressure Fuel Pump Replacement