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Error Code P0190 is described as Fuel Rail Pressure Sensor Circuit Malfunction. This code is strictly about the incoming signal from the FRP (fuel rail pressure) sensor falling below the calibrated limit for a certain period of time. This code can either be a mechanical or electrical problem, which largely depends on the manufacturer, fuel system or fuel type of the vehicle.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II equipment, particularly fuel injected engines, both gas and diesel vehicles made in 2000 up to present., and usually to manufacturers such as Ford, GMC, Volvo, Volkswagen, etc. Specifications on the definition, troubleshooting and repair of course, vary from one make/model to another.
Error Code P0190 appears when the PCM (powertrain control module, also known as ECM or engine control module) has determined a problem in the fuel rail pressure sensor, particularly on its ability to stay within range. The range has been set by the manufacturer. When the PCM determines the particular sensor is outside its predetermined range, it triggers the Check Engine light and registers the trouble code.
Symptoms for this error code include:
- Hard or no starting at all
- Engine cranks but will not start
- Engine hesitates upon acceleration
- Lack of power
Potential causes for this error code are:
- Damaged FRP sensor
- VREF open circuit
- VREF having excessive resistance
- Bad fuel pump, fuel pump driver or relay
- Vacuum leaks
- Clogged fuel filter
- Exposed, damaged, corroded or melted wiring or connectors
- Low or no fuel
How to Check
Mechanics diagnose this code by inspecting the wiring in the FRP sensor and injectors. They will search for broken, corroded, or melted wires and conduct the necessary repairs.
Then, they will proceed to use the OBD-II scanner, record the free frame data as well as other registered trouble codes in the PCM.
After clearing the trouble codes, the vehicle will be taken for a test drive. If the code doesn’t come back right away, then that means the problem is intermittent.
If the code comes back however, the mechanic will proceed by using the fuel pressure gauge to check the fuel pressure. If there’s a low pressure, then there’s a good chance there’s no gas. If the vehicle does have gas however, they will proceed on checking the fuel pump and make sure it’s running properly.
If the vehicle will not start but the fuel pump is still running, there’s a good chance the fuel filter is clogged, or there’s an issue in the fuel injector circuits and/or the PCM.
If the fuel pump doesn’t make a sound, they will check whether it’s defective by tapping the tank and try to start the car.
If the vehicle starts successfully, that means the fuel pump is damaged and must be replaced. If the car doesn’t start, they will proceed by testing the voltage at the fuel pump connector and see if the fuel pump relay, fuse, and PCM circuitry should be inspected. If all three are operational, they will proceed with checking the FRP sensor itself.
From here, they will check the wiring of the sensor and look for signs of broken or melted wiring.
Then, they will use their OBD-II scanner to determine whether the FRP sensor is still operational. If the wires pass the inspection and the FRP still doesn’t work properly, that means the sensor must be replaced.
In some rare occasions however, the problem is caused by bad PCM. With this, the mechanic will need to go through advanced diagnostics to prove it’s what is causing the problem.
How to Fix
Repairs for this code are pretty straightforward, and you can definitely pin point the necessary repairs based on your diagnosis. Common fixes include:
- Checking of the fuel level and refilling the tank if necessary
- Repair or replace corroded connectors or wirings
- Repair or replace broken or shorted wires
- Replace clogged fuel filter
- Replace fuel pump, fuse and/or relay
- Replace FRP sensor
Error Code P0190 is considered a serious problem, as the drivability issues make driving difficult and dangerous. Thus, it definitely requires immediate attention.
In many cases, the problem is caused by empty fuel tank, and simply filling the gas tank can resolve the problem. Fuel rail pressure sensor replacement must not be your first option for repair.