What is OBD-II Code P0090 – Fuel Pressure Regulator A Control Circuit/Open

What is OBD-II Code P0090 – Fuel Pressure Regulator A Control Circuit/Open

As a mechanic, one of the most important tools in diagnosing engine problems is the On-Board Diagnostics (OBD) system. OBD-II is the second generation of this system, which has been used since 1996. This system provides a standard set of diagnostic codes that help to identify engine and vehicle problems. One of these codes is the P0090 code, which relates to the fuel pressure regulator A control circuit being open.

In this article, we will be looking at what the P0090 code means and how to repair its underlying issue. We will also be providing additional information and examples to help you better understand this code.

What is the P0090 Code?

The P0090 code indicates that there is an issue with the fuel pressure regulator A control circuit. This means that the engine control module (ECM) has detected that there is an open circuit in the control circuit. The fuel pressure regulator is an important part of the fuel system and is responsible for maintaining a consistent and optimal fuel pressure to the fuel injectors.

The fuel pressure regulator A control circuit is responsible for sending signals to the ECM about the fuel pressure regulator’s operation. If the circuit is open, the signals cannot be transmitted, and the fuel pressure regulator will not be able to function optimally. This can cause various engine problems and can eventually cause the vehicle to stall.

What are the Causes of the P0090 Code?

There are several causes of the P0090 code, including:

1. Faulty fuel pressure regulator: A malfunctioning fuel pressure regulator can cause the circuit to be open and trigger the P0090 code.

2. Wiring issues: Damaged or corroded wiring can cause open circuits and prevent the fuel pressure regulator’s signal from being transmitted to the ECM.

3. Faulty ECM: A malfunctioning ECM can sometimes cause the P0090 code to appear.

4. Loose or damaged connectors: Damaged or loose connectors can cause the fuel pressure regulator control circuit to become open.

What are the Symptoms of the P0090 Code?

When the P0090 code appears, several symptoms can indicate that there is an issue with the fuel pressure regulator’s control circuit. These symptoms include:

1. The engine is difficult to start: Because the fuel pressure regulator cannot regulate fuel pressure accurately, the engine may be challenging to start or may fail to start altogether.

2. Poor engine performance: If the fuel pressure regulator is not functioning correctly, the engine’s performance may be affected, and it may run roughly.

3. Decreased fuel efficiency: When the fuel pressure regulator is not functioning correctly, the engine may use more fuel than necessary, reducing fuel efficiency.

4. Failed emissions testing: If the P0090 code appears, the vehicle is unlikely to pass a required emissions test.

How to Fix the P0090 Code

When trying to fix the P0090 code, it is important to understand that several underlying issues can cause this problem. Therefore there is no one-size-fits-all way to fix this code. However, the following steps can help:

1. Use an OBD-II scanner to retrieve the code and check freeze frame data. Freeze frame data can provide additional information that can help in identifying the cause.

2. Check the wiring and connectors for any damage or corrosion. Repair or replace any damaged parts.

3. Check the fuel pressure regulator’s operation, and if defective, replace it.

4. Repair or replace any faulty ECM components.

5. Use the scanner to clear the code and monitor the readiness status to ensure that the issue has been resolved.

Frequently Asked Questions

Q: Can the P0090 code appear without the check engine light coming on?

A: No, the Check Engine Light will indicate that the P0090 code has been triggered.

Q: What happens if I ignore the P0090 code?

A: Ignoring the P0090 code can cause damage to the engine and other components. It can also cause the vehicle to stall or fail to start.

Q: Can I drive my vehicle with the P0090 code appearing?

A: While you can still drive your vehicle with the P0090 code appearing, it is not recommended as it can cause severe engine damage or result in the car failing to start.

Q: How much does it cost to fix the P0090 code?

A: The cost of fixing the P0090 code depends on the underlying issue. It can cost anywhere from $50 to $1000.

Q: What is the best way to prevent the P0090 code from occurring?

A: Regular vehicle maintenance, including fuel system checks and replacing damaged or corroded wires, can prevent the P0090 code from occurring.


The P0090 code indicates an issue with the fuel pressure regulator A control circuit being open, which can cause the vehicle to stall and lead to engine damage. Several issues can cause this code to appear, including faulty fuel pressure regulator, wiring issues, and malfunctioning ECMS. To resolve this issue, a mechanic needs to check wiring, fuel pressure regulator operation, and replace any faulty components. Remember, regular vehicle maintenance can prevent the P0090 code from appearing.

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