Technical Description of OBD-II Trouble Code
The control circuit for Fuel Pressure Regulator 1 is open.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles (GMC, Chevy, Chrsyler, Dodge, Jeep, Mitsubishi, VW, Toyota, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
A stored code P0090 indicates that the powertrain control module (PCM) has detected an open control circuit in the electronic fuel pressure regulator (designated 1). This designation is used in systems that have multiple electronic fuel pressure regulators. This designation may refer to the engine bank, but not exclusively. Additionally, the word “open” could be replaced with “disconnected” or “broken.”
The PCM typically controls the electronic fuel pressure regulator. A battery voltage signal and a ground signal are used to control a servo motor that positions a valve to achieve the desired level of fuel pressure for any given circumstance. When voltage is applied to the servo motor, the valve opens incrementally and fuel pressure increases. When voltage is decreased, the servo retracts and a strong spring closes the valve, decreasing fuel pressure.
The fuel pressure sensor, usually located in the fuel injector rail, allows the PCM to monitor fuel pressure and adjust fuel pressure regulator voltage accordingly.
The fuel pressure regulator and fuel pressure sensor may be separate components, but they are often integrated into a single housing with one electrical connector.
If the actual fuel pressure does not meet the desired fuel pressure calculated by the PCM, a P0090 code may be stored and the malfunction indicator lamp (MIL) may illuminate.
Related fuel pressure regulator engine codes:
Symptoms & Severity
Excessive fuel pressure can cause various drivability issues and damage to the internal engine and catalytic converter. Therefore, a code P0090 should be considered severe.
Symptoms of a P0090 code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
Diagnosing a code P0090 will require a diagnostic scanner, a digital volt/ohmmeter (DVOM), a suitable fuel pressure gauge, and a reliable vehicle information source (such as All Data DIY).
NOTE: Exercise extreme caution when connecting a manual fuel pressure gauge, as high pressure fuel that comes into contact with hot surfaces or open sparks could ignite and cause a dangerous vehicle fire.
Begin by visually inspecting the system wiring and connectors, focusing on harnesses and connectors on top of the engine. Pests in cold climates are attracted to this area due to the warmth, and they can damage (gnaw) the system wiring and connectors.
Next, connect the scanner to the vehicle diagnostic port and retrieve the stored codes and freeze frame data. Write down this information, as it may be helpful during the diagnostic process. Clear the codes and, if possible, test-drive the vehicle.
If the code is immediately reset, check for voltage and ground at the fuel pressure regulator. If no voltage is found, test the power supply relays and fuses according to the wiring diagram from the vehicle information source. If there is no ground, follow the wiring diagram to locate the appropriate location of the fuel pressure regulator control system ground(s) and ensure that all connections are secure.
If there is voltage and ground at the fuel pressure control regulator, obtain fuel pressure specifications from the vehicle information source and test the fuel system pressure using the fuel pressure gauge. Follow the manufacturer’s recommendations for connecting the fuel pressure gauge and observe the fuel system data on the scanner while visually monitoring the manual fuel pressure with the gauge. If the fuel pressure displayed on the scanner does not match the actual fuel pressure, suspect a faulty fuel pressure sensor.
Fluctuations in actual fuel pressure should occur with variations in fuel pressure regulator control voltage. If this is not the case, suspect that the fuel pressure regulator is defective, there is an open or shorted circuit in one of the fuel pressure regulator control circuits, or the PCM is faulty.
Follow the manufacturer’s recommendations for testing the electronic fuel pressure regulator and the individual fuel pressure regulator control circuits with the DVOM. Disconnect controllers from the circuit before testing with the DVOM to prevent damage to control modules.
Additional diagnostic notes:
Other fuel pressure trouble codes include:
