Technical Description of OBD-II Trouble Code
Circuit for Fuel Rail Pressure Sensor “A”
What is the meaning of this code?
This generic code is applicable to most fuel injected engines, both gasoline and diesel, manufactured since 2000. It is relevant to all car manufacturers such as Volvo, Ford, GMC, VW, etc.
This code specifically deals with the issue of the incoming signal from the fuel rail pressure (FRP) sensor falling below a calibrated limit for a specific duration. The fault can be either mechanical or electrical, depending on the vehicle manufacturer, fuel type, and fuel system.
The troubleshooting steps may vary depending on the manufacturer, type of fuel rail pressure system, and type of fuel rail pressure sensor and wire colors.
Symptoms
The symptoms of an engine code P0190 may include:
Causes
The potential causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) specific to your vehicle. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during diagnosis.
Next, locate the Fuel Rail Pressure Sensor on your vehicle. It may have a similar appearance to the one shown in the image below:
Once located, visually inspect the connectors and wiring. Look for any signs of chafing, rubbing, bare wires, burn spots, or melted plastic. Separate the connectors and carefully examine the terminals (the metal parts) inside. Check for signs of corrosion, burning, or a green color, which is abnormal compared to the usual metal color. If necessary, use Electrical Contact cleaner or rubbing alcohol and a light plastic bristle brush to clean the terminals. After cleaning, let them air dry and apply some dielectric silicone compound to the contact points.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if this code reappears. If it doesn’t, then the issue was most likely related to the connections.
If the code does reappear, further testing of the sensor and its associated circuits is necessary. Typically, there are 3 wires connected to the FRP sensor. Disconnect the harness connected to the FRP Sensor and use a Digital Volt Ohm Meter (DVOM) to test the 5V power supply circuit (Red lead to the 5V power supply circuit, black lead to a good ground). If there is 12 volts instead of 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts or consider a possible issue with the PCM.
If the power supply circuit is functioning correctly, use a DVOM to check if there is 5V on the FRP Sensor signal circuit (Red lead to the sensor signal circuit, black lead to a good ground). If there is no 5 volts or if you measure 12 volts, repair the wiring from the PCM to the sensor or consider a possible issue with the PCM.
Next, check if there is a good ground at the FRP sensor. Connect a test light to the positive terminal of a 12V battery and touch the other end of the test light to the ground circuit connected to the FRP Sensor circuit ground. If the test light does not illuminate, it indicates a problem with the circuit. If the test light illuminates, wiggle the wiring harness connected to the FRP sensor to check for any flickering of the test light, which indicates an intermittent connection.
If all the tests have passed and you still receive a code P0190, it is likely that the PCM has failed. Before considering a PCM replacement, it is recommended to perform a hard reset (disconnecting the battery). Additionally, the Fuel Rail Pressure Sensor may need to be replaced.
CAUTION! For diesel engines with Common Rail Fuel Systems: if a fuel rail pressure sensor is suspected, it is advisable to have a professional technician install the sensor. This sensor may be installed separately or as part of the fuel rail. In either case, the fuel rail pressure on these diesel engines is generally no less than 2000 psi at warm idle and can exceed 35,000 psi under load. If not sealed properly, this fuel pressure can cause cuts on the skin, and diesel fuel contains bacteria that can cause blood poisoning.
