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When the input from your vehicle’s sensors or output devices do not match the expected values, the powertrain control module (PCM) stores the issue as a trouble code. A trouble code is a combination of letters and numbers that indicate the potential location and nature of a problem within your vehicle.

The P0090 is a trouble code that indicates a potential issue with the fuel pressure regulator circuit. Find out more about this code, its causes, and symptoms with this brief guide.

What Does the P0090 Code Mean?

Diagnostic trouble code (DTC) P0090 stands for “Fuel Pressure Regulator Control Circuit/Open.” This code sets when the PCM has determined that there is an open control circuit in the electronic fuel pressure regulator. This code may also set when the PCM is unable to control the fuel pressure regulator, or if the actual fuel pressure does not match the desired fuel pressure.

fuel pressure regulator P0090
The P0090 is a trouble code that indicates a potential issue with the fuel pressure regulator circuit.

In some vehicles, this code is defined as “Fuel Pressure Regulator 1 Control Circuit/Open”. The “regulator 1” in this code’s definition refers to the designated 1 fuel pressure regulator. Designation is typically used in systems that have multiple electronic fuel pressure regulators. In some cases, the designation may refer to the engine bank. However, this may not be the case for other vehicles.

Note: The definition of code P0090 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

The fuel pressure regulator, together with the fuel pump, maintains the required pressure drop at the fuel injector tips. This component typically has a spring-loaded, diaphragm-operated valve in a metal housing. The fuel pressure regulators on fuel-return-type injection systems are mounted on the return or downstream side of the injectors at the end of the fuel rail.

A battery voltage signal and a ground signal are used to control the fuel pressure regulator servo motor. The servo motor positions a valve in such a way that the desired fuel pressure may be achieved. When voltage is applied to the fuel pressure regulator servo motor, the valve is opened in small increments, increasing the fuel pressure level. When the voltage is increased up to a certain point, the motor retracts a spring that forces the valve to close and the fuel pressure to drop.

The PCM monitors the fuel pressure using a fuel pressure sensor located in the injector rail. This allows the PCM to control the fuel pressure regulator voltage according to the demands of the system. The fuel pressure regulator and the fuel pressure sensor are two separate components that are typically enclosed together in a single housing with a single electrical connector.

Some vehicle models are more prone to code P0090 than others. Have a technician check your vehicle immediately if you own a Mazda (especially Mazda Protege), Nissan, Volvo, or Chevrolet and your diagnostics show P0090.

car ECM
Issues with the PCM can trigger the P0090 code.

What are the Possible Causes of the P0090 Code?

There are multiple possible causes for each diagnostic trouble code. After all, a DTC indicates the nature and potential source of the problem and not the specific root cause. Below are just some of the possible causes of the P0090 trouble code:

  • Wiring issues, such as shorted or open wiring and/or connectors in the fuel pressure regulator control circuit
  • Defective fuel pressure regulator
  • Faulty fuel rail pressure sensor
  • Faulty PCM
  • PCM programming error

What are the Common Symptoms of the P0090 Code?

When some OBD-II codes set, there may be a few noticeable signs of a potential issue. However, this might not always be the case, as other OBD-II codes may only cause the PCM to trigger the check engine light. As for the P0090 code, below are some of its most common symptoms:

  • Check engine light/malfunction indicator lamp illuminated
  • Delayed startup
  • Black smoke from the exhaust
  • Decreased fuel efficiency
  • Decreased engine performance
  • Presence of other engine drivability codes

How to Diagnose the P0090 Code

Troubleshooting OBD-II codes may seem intimidating for some because there are multiple possible causes for each trouble code. Without the proper technical knowledge, tools, and resources, it will be difficult to diagnose and repair the P0090 fault code.

However, there are several sources you can use to help you understand the issues behind the DTC P0090 better. Repair manuals and databases are the best primary sources for code P0090 troubleshooting information. Not only do these sources contain detailed instructions, but they also have helpful diagrams and illustrations, which make it easier to understand automotive concepts.

Aside from repair manuals, there are also other credible sources online, such as how-to videos and blog articles.

delayed startup car engine
Delayed startup is one of the noticeable signs of P0090 code.

How to Fix the P0090 Code

As mentioned above, there are several possible reasons why an OBD-II code, such as P0090, may set. This makes OBD-II code diagnosis and repair challenging for many DIYers. Another factor that comes into play is that repair instructions differ depending on the vehicle’s manufacturer. This means that the solution to the P0090 in Nissan vehicles may not address P0090 in Mazda vehicles.

If you’re a seasoned DIYer, you can fix the DTC P0090 on your own, as long as you have the right tools and a reliable repair manual or repair database subscription. However, if you’re not confident in your repair skills, you can have a certified mechanic or technician do the repairs for you.

Other Notes About P0090

The P0090 fault code points to a potential issue with the circuitry of your vehicle’s fuel pressure regulator. You’ll need to address this code right away to avoid internal engine damage and catalytic converter problems. Unregulated fuel pressure may also lead to several drivability issues.

The P0090 code has several related codes, such as the P0089 (Fuel Pressure Regulator 1 Performance), P0091 (Fuel Pressure Regulator 1 Control Circuit Low), and P0092 (Fuel Pressure Regulator 1 Control Circuit High).

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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