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Error Code P0193 is described as Fuel Rail Pressure Sensor Circuit High Input. Meaning, the PCM (powertrain control module, also known as ECM or engine control module) has determined that the fuel pressure is outside the predetermined range of the vehicle’s manufacturer.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II equipment, more specifically to fuel injected engines, both gas and diesel vehicles made in 2000 up to present. It’s used by manufacturers such as Ford, GMC, Volvo and Volkswagen. Specifications on the definition, troubleshooting and repair of course, vary from one make/model to another.
The PCM needs to know the fuel pressure at all times so it can control the fuel injectors effectively and deliver the right amount of fuel to the engine’s combustion chamber and allow it to have the maximum power and fuel economy, all while maintaining the lowest possible emission on the tail pipe.
Error Code P0193 is about the incoming signal from fuel rail pressure sensor and set when the PCM reads the signal is above calibrated limit for a specified amount of time, indicating the fuel pressure condition is abnormally high. Depending on the make and model of the vehicle, this can be a mechanical or an electrical fault.
As with other error codes, this trouble code illuminates the check engine light. Other symptoms include:
- Engine hesitation or stalling
- Engine cranks but will not start
- Engine dies or stall at stop signs
- Excessive fuel consumption
- Either Rich fuel trim (P0172)
- Tail pipe emission has unusual smell
- Vehicle fails emission test
Some of the most common causes of this error code include:
- Low or high fuel pressure
- Low or no fuel
- Defective FRP sensor, circuit or connector
- Defective fuel pressure regulator
- Vacuum leaks
- Excessive circuit resistance
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 on using 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 considered intermittent.
If the vehicle refuses to start, then there’s a good chance there’s not enough fuel inside the fuel tank. Using a fuel pressure gauge, test the fuel pressure. If the test says low fuel pressure, that means there is little to no fuel in the tank.
Make sure the pump is running properly, mechanics usually conduct a test by listening to it. If the car still won’t start, but there’s a sound you can hear from the fuel pump, then there must be a problem in the fuel injector circuitry or a clogging in the fuel filter.
If the vehicle still refuses to start and the mechanic cannot hear the fuel pump, they will test it further by starting the car with another person tapping on the bottom of the fuel tank. If the car starts after that, then that suggests a defective fuel pump, and it must be replaced.
If the fuel pump is okay and the car still doesn’t start, the mechanic will proceed on checking the battery voltage at fuel pump connector. If he determines there is no voltage from the battery, then he will proceed on checking any faults on the fuse circuit, fuel pump relay circuit, and the PCM circuit.
If these components are running in good condition, the mechanic will proceed to check the fuel rail pressure sensor. Using a digital volt ohmmeter, he will test the sensor for reference voltage while the vehicle is running. The reading must be 5V. If it’s in good condition, he will then check the ground wire.
If both the reference signal and ground wire are in good condition, he will then proceed to check the sensor resistance. If this sensor doesn’t meet the specifications set by the manufacturer, then that means the fuel rail pressure sensor must be replaced.
If both the circuitry and the sensors are working properly, that may suggest a problem in the PCM. This is a rare condition, but would need reprogramming, if not replacement.
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
One of the most common mistakes people do when dealing with this trouble code is overlooking other components and proceeds on repairing or replacing the fuel trail pressure sensor.
In many cases, the problem is caused by an empty fuel tank, and simply filling the gas tank can resolve the problem. A fuel rail pressure sensor replacement must not be your first option for repair.