Error Code P0090: What It Means & What To Do?

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Is your car engine not starting again? Do you notice increased fuel consumption over recent period of time? And is your car engine performance degrading? If all this is true, then there might be a problem with the Fuel Pressure Regulator Control Circuit indicating the OBD Code P0090 error.

OBD-II Code Decreased engine performance is defined as a Fuel Pressure Regulator 1 Control Circuit/Open

High fuel pressure is necessary, to overcome cylinder pressures, as direct injections systems need to inject fuel on the compression stroke, unlike low-pressure port fuel injection systems, which injects fuel into a partial vacuum. At the same time, such high fuel pressures can be inherently dangerous and destructive, which makes fuel pressure regulation critical. Within specifications, high fuel pressure is necessary and expected. Low fuel pressure would result in poor engine performance and fuel economy. On the other hand, a spike in fuel pressure could actually damage the system.

The engine control module (ECM) controls fuel rail pressure (FRP) by modulating the FRP regulator, using feedback from the FRP sensor. If the ECM detects a problem in the FRP regulator circuit, it will set a DTC (diagnostic trouble code), P0090 Fuel Rail Pressure (FRP) Regulator Control Circuit Malfunction, and illuminate the MIL (malfunction indicator lamp).

What causes the problem of Fuel Pressure Regulator 1 Control Circuit?

• Defective Electronic Fuel Pressure Regulator
• Faulty Fuel Pump
• Faulty Fuel Pump driver/relay
• Defective Fuel Rail Sensor
• Open/short electrical wiring and connections
• Faulty ECM/PCM

1. Fuel Pressure Regulator Control Valve - Minor issue with the valve can also vary the fuel pressure into the engine thus impacting the combustion process and degrading the engine performance. Replace old and damaged valves now.
2. Electronic Control Module - OBD Error Code P0090 can also be due to faulty EVMs. This may lead to engine stalling or not starting, and check engine lights being on. It’s better to get the faulty electricals replaced as soon as possible.
3. Fuel Pressure Regulator - P0090 error code may also flash due to problems with the pressure regulator. Irregular fuel pressure in turn hampers the engine’s performance. Replace the fuel pressure regulator now.
4. Fuel Pump - A damaged fuel pump will not be able to supply proper fuel to the engine resulting in engine stalling and sometimes not starting resulting the OBD error code P0090. Immediate replacement of fuel pump is advisable.
5. FVR Wiring/Harness - This harness in a link between different components of the car and collects data to be later converted into meaningful information for decision making. Thus, this part should always be checked for any faults or damages and immediately replaced.
6. Diagnostic Tool - In order to be that DIY guy, you need few diagnostic tools to get your car problems pointed out easily. Our diagnostic tools collection will come handy to do so, so why not have a look?

Common symptoms include no start condition, extended cranking before engine starts, loss of acceleration, and reduced fuel mileage, along with a stored trouble code and Check Engine Light illumination. Other major symptoms include engine misfire codes, lean and/or rich exhaust codes, and mass airflow sensor codes.

Common Symptoms

• Engine Running Poorly
• Engine gone into failsafe mode
• Check Engine Light illumination
• Reduced Fuel Economy

Use a DVOM (digital volt-ohm meter) to diagnose this OBD code problem. Focus your attention on the FRP regulator and the harness between the FRP regulator and the ECM. The FRP regulator may be mounted on the fuel rail or on the high-pressure pump.

• Wire Harness and Connector Check – Make sure the wire harness is free of damage. Make sure the FRP regulator connector is in good condition, no bent or blacked-out pins, corrosion, or water entry, and is firmly seated. Repair as necessary.
• FRP Regulator Circuit Check – FRP regulator is disconnected and checked for resistance. Check the repair manual for proper resistance specifications. If there is excessive coil resistance or a short to ground, replace the regulator.

Checking for any diagnostic trouble codes (DTC’s). DTC’s will have freeze frame data associated with each code that this tells us important information for the test drive.

• Next, clear the code and performed a road test. The road test should be under similar conditions to the freeze frame data.
• A visual inspection is performed to look for any damaged or broken wiring, sources of poor connection, and proper operation of the fuel pressure sensor.
• An OBD-II scan tool will be used to monitor fuel pressure control system operation. If the fuel pressure regulator control solenoid operates properly, then a manufacturer specific ECM test must be performed and the faulty components should be replaced.

Common Mistakes When Diagnosing The P0090 Code

When steps are not followed in order or are skipped altogether, then there are chances of misdiagnosis. Though the fuel pressure regulator is the typical cause, it must be tested before it is condemned and replaced. This will prevent repairs from being performed that do not address the actual fault. Also, check for faulty wiring and connections to avoid unnecessary costly diagnosis.