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 01: Fuel Pressure Regulator Solenoid 1 Control Circuit Short to Battery
DTC P0090 02: Fuel Pressure Regulator Solenoid 1 Control Circuit Short to Ground
DTC P0090 04: Fuel Pressure Regulator Solenoid 1 Control Circuit Open
DTC P0090 54: Fuel Pressure Regulator Solenoid 1 Control Circuit High Temperature

### Circuit/System Description

The fuel pressure regulator solenoid 1 is used to control the fuel pressure from the high pressure fuel pump to the fuel rail. The fuel pressure regulator solenoid 1 is pulse width modulated (PWM). An ignition voltage is supplied to the fuel pressure regulator solenoid 1. The ECM controls the solenoid by grounding the control circuit with a solid state device called a driver.

### Conditions for Running the DTC

• | The ignition is ON, or the engine is running.

• | The ignition voltage is less than 16 volts.

• | The DTCs runs continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0090 02

The ECM detects the fuel rail pressure regulator solenoid 1 control circuit is open for less than 1 second.

#### P0090 04

The ECM detects the fuel rail pressure regulator solenoid 1 control circuit is shorted to ground for less than 1 second.

#### P0090 01, P0090 54

The ECM detects the fuel rail pressure regulator solenoid 1 control circuit is shorted to voltage for less than 1 second.

### Action Taken When the DTC Sets

DTC P0090 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P0090 is a Type B DTC.

### 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. Ignition ON, observe the DTC information with a scan tool. DTCs P0090, P0091, or P0092 should not set.
2. 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 Q18 fuel rail pressure regulator solenoid 1.
2. Ignition ON, verify a test lamp illuminates between the ignition 1 voltage circuit terminal 1 and ground.

⇒ | If the test lamp does not illuminate, repair the ignition 1 voltage circuit for a short to ground or an open/high resistance.

3. Ignition ON, test for 3-4 V between the control circuit terminal 2 and ground.

⇒ | If less than the specified range, test the control circuit for an open or a short to ground. If circuit tests normal, replace the K20 ECM.

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If circuit tests normal, replace the K20 ECM.

4. Ignition OFF, test for less than 5 Ω between the control circuit terminal 2 and the K20 ECM.

⇒ | If greater than the specified range, repair the control circuit for a high resistance.

5. If all circuits test normal, test or replace the Q18 fuel pressure regulator solenoid 1.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the Q18 fuel rail pressure regulator solenoid 1.
2. Test for 2-4 Ω between the control terminal 2 and the ignition 1 voltage terminal 1.

⇒ | If not within the specified range, replace the Q18 fuel pressure regulator solenoid 1.

3. Test for infinite resistance between each terminal and the fuel pressure regulator solenoid 1 housing.

⇒ | If not the specified value, replace the fuel rail pressure regulator solenoid 1.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Fuel Injection Pump Replacement

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

### Repair Verification

Ignition ON, observe the scan tool DPF soot accumulation parameter. The parameter should be less than 24 grams.

⇒ | If greater than the specified range, perform a DPF service regeneration. Refer to Exhaust Particulate Filter Cleaning.