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.
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.
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.
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.
P0090 and Common Rail Fuel Systems
P0090 is a very important code on vehicles that use “common rail” fuel injection (CRI), such as light truck diesel engines, i.e., the GM Duramax Diesel, Ford Powerstroke, or Dodge Cummins. This code is also listed on certain gasoline direct injection (GDI) platforms, which are also common rail fuel systems.
The fuel rail on GDI or Common Rail Diesels has a feedback sensor that the ECM uses to determine what needs to be done with the High Pressure Pump solenoid in order to meet the necessary pressure target.
Code P0090 points to a problem with the pump solenoid circuit. The Fuel Pressure Regulator solenoid has different names on different platforms, but it typically always does the same job. Both sides of the pressure control solenoid circuit are typically switched by the PCM/ECM, a design for solenoid control that is becoming very common on newer platforms, even for injector operation.
Some of the high pressure pumps default to high pressure when the solenoid circuit is open (no voltage at the solenoid) – others default to low pressure. A system that defaults to low pressure will usually idle but will have very little power. The systems that default to high pressure will snort and carry on like a plug wire is crossed.
NOTE: If any of the fuel supply lines or the fuel rail pressure sensor are removed on a common rail system, the component must be replaced, so don’t remove a line or a sensor unless you have a new one with which to replace it. The soft iron seat will only seal once.
Also, DO NOT remove any fuel line unless you know for sure there’s no pressure in the rail to avoid serious injury.
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.
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).
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