P0194 - OBD Trouble Code

<<See All OBD Codes

Is your vehicle’s Check Engine Light illuminated? Are you experiencing sudden decrease in engine power and acceleration? Is there a drop in the fuel economy with increased level of emissions? All these indicate problem with the fuel delivery system and the Powertrain Control Module, thus flashing OBD Code P0194 error.

The Fuel Rail Pressure (FRP) sensor is a diaphragm strain gauge device where, change in resistance is directly proportional to change in pressure. This varying resistance affects the voltage drop across the sensor terminals and provides electrical signal to the Powertrain Control Module (PCM) corresponding to pressure. Such strain gauge type sensors are considered passive sensors.

A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal should be equal to the reference voltage minus the voltage drop across the fixed resistor. The FRP sensor measures the pressure of the fuel near the fuel injectors and this signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each combustion cylinder.

If the PCM detects a problem with the fuel rail pressure sensor (RPS), such as insufficient or excessive voltage feedback, or an open or short circuit, it locks out the high-pressure pump and put the engine into fail safe mode. The MIL (malfunction indicator lamp) gets illuminated, and an OBD code will be set in PCM/ECM memory. OBD P0194 error can be defined as Fuel Rail Pressure Sensor Circuit Intermittent.

What causes the problem of Fuel Rail Pressure Sensor Circuit Intermittent?

• Confined fuel filter
• Cramped fuel supply line
• Faulty FRP sensor and wirings
• Damaged connections to the sensor circuit
• Blemished or worn fuel pump
• Fuel splattering due to low fuel level
• Sudden acceleration/deceleration
• Vehicle inclining on hilly or steep roads

1. Fuel Pressure Regulator - Facing problem with the fuel pressure regulator? Buy new one now!
2. Fuel Pump - If your fuel pump is not working to its potential, it better to replace it with a new one. Buy quality products from us.
3. Fuel Filter - A fuel filter is a filter in the fuel line that screens out dirt particles from the fuel, normally made into cartridges containing a filter paper. They are found in most internal combustion engines. Fuel filters serve a vital function in today's modern, tight-tolerance engine fuel systems. Replace old and clogged fuel filters now!
4. Fuel Pump Relay - The fuel pump ca fails due to faulty relay too. Replace it with a new one.
5. Fuel Pump Fuse - Keep checking for blown fuses and replace them as necessary.
6. Fuel Pressure Sensor - This component is important to the fuel delivery system and has to be replaced if faulty.
7. Fuel Pressure Gauge - Check if the gauge is giving the right reading and if not, replace it with a new one.
8. Fuel Line Assembly - Check for damaged to the fuel line assembly unit and replace it if it can’t be repaired.
9. Diagnostic Tools - Choose from our wide variety of diagnostic tools to detect and correct the OBD code error.

The engine control module (ECM) uses pressure sensors to determine the pressure in the fuel system. If the voltage goes beyond limits, the PCM will set code P0194. Some of the prime symptoms of this problem are mentioned below;

Common Symptoms

• Low engine power and limited output
• Abnormal throttle response and hard cold starting
• Declined fuel economy
• Sluggish Engine and lot of noise
• Engine smoking on start-up with increased emissions

• Check for fuel levels and refill
• Repair broken or shorted wires
• Replacement of clogged fuel filter
• Replacement of fuel pump relay
• Replacement of fuel pump fuse
• Replacement of fuel pump
• Replacement of fuel rail pressure sensor

At Parts Avatar Canada, get quality replacement parts and performance parts at the best prices for all your car makes and models.

• Check the wiring and connectors for melted wires, broken wires, & corrosion, and repair the wiring and connections if necessary.
• Use an OBD-II scanner to retrieve freeze frame data and trouble codes stored by the power control module. Test drive the car, after clearing the codes, to see if the P0194 trouble code returns.
• If the OBD code P0194 does not return immediately, this indicates the possibility of an intermittent issue and can be hard to resolve.
• Check for the fuel in the fuel tank if the car doesn’t start. Use a fuel pressure gauge to test the fuel pressure. Low fuel pressure is an indication that the car has little to no fuel.
• To make sure the fuel pump is operating properly, listen to it carefully. If the car won’t start, but they can still hear the fuel pump, the fuel injector circuitry could be faulty or a fuel filter could be clogged.
• If the car won’t start and you also cannot hear the fuel pump, then try starting the car while another person taps on the bottom of the fuel tank. If the car starts, this means that the fuel pump needs to be replaced.
• Check the battery voltage at the fuel pump connector. If there is no battery voltage at the fuel pump connector, check the fuse circuit, fuel pump relay circuit, and power control module circuit for any faults.
• If these components are operational, check the fuel rail pressure sensor. Test the reference voltage of the fuel rail pressure sensor, using a digital volt ohm meter, while the car is running. The voltage reading should be 5-volts. If this test is successful, test the ground wire.
• Test the sensor resistance next. If the sensor resistance test results do not meet the manufacturer’s specifications, the fuel rail pressure sensor might be faulty and needs replacement.

Common Mistakes When Diagnosing The P0194 Code

Most of the time we tend to diagnose the problem without completely identifying the real cause of it. It is important to follow all the diagnostic steps and examine each component carefully before correcting. Some of the components to be focused on are listed below;

• Clogged fuel filter
• Fuel pressure regulator failure
• Fuel pump failure
• Leaking fuel lines
• Powertrain Control Module (PCM) failure
• Wiring/harness issue