You can find information about the P0191 fault code on this page.
We have given it a seriousness of 7/10 with 1 being the least serious and 10 being the worst.
Looking To Fix This Yourself?
By using a workshop/repair manual you could diagnose and even fix this issue yourself.
You can find a collection of free manuals containing loads of information specific to your car on our partner site.View Workshop/Repair/Service Manuals »
Fault code P0191 is logged when the powertrain control module (PCM) has detected an issue within the fuel rail pressure sensor circuit.
This happens when the signal received from the sensor does not match the expected value that is calculated by the PCM.
The fuel rail, which is used in common rail fuel injection systems, is a component that is critical to supplying fuel to the various fuel injectors in the engine. The fuel rail sensor is used to signal the amount of fuel flowing through the rail at all times.
This signal, given as a voltage, is then sent to the PCM to determine air-fuel mixture parameters for increased performance and efficiency.
Other Signs of This Problem
There can be several fairly noticeable signs of this issue when it comes to changes in the performance of the engine. However, it is possible that there will be no noticeable symptoms at all.
The most obvious sign will be the Check Engine light on the dashboard.
Other signs will be related to decreased driveability. These can be things like the engine running lean. This will likely result in fault code P0171 being logged.
Other issues like increased fuel consumption and running rough can also occur.
What Could Be The Problem?
The cause for this issue will likely be found within the fuel rail pressure sensor circuit itself, rather than an actual issue within the fuel system.
One of the most likely causes is a fault in the circuit. These can be things like damaged wiring and loose or corroded connections in the circuit.
Additionally, a faulty fuel rail pressure sensor can be the cause as well. This can be a result of damage or a simple defect.
Outside of the sensor circuit itself, it is possible that there is insufficient or excessive fuel pressure. This can be a result of a wide array of things like defective parts or leaks.
In rare cases, the PCM itself can be at fault. However, this will likely come with a number of other fault codes being logged as it malfunctions.
The fixes will likely be found within the fuel rail pressure sensor circuit due to the nature of the fault code. This means the fix will likely require electrical skills. The issue may require parts to be replaced as well.
Any other logged codes that relate to the fuel system should be fixed first.
If the fuel pressure sensor is faulty, it should be replaced.
Any damaged wires or loose connections need to be fixed or replaced.
If the PCM is running on outdated software, an update needs to be installed. Additionally, if the PCM is defective, it needs to be replaced.
Fault code P0191 should be considered a moderately serious issue. It can decrease the driveability of the vehicle and in some cases cause damage to the various components in the engine.
It is a good idea to have this issue fixed immediately.
Popular Fault Codes
These are the most popular fault codes that people are searching for.
Intake Camshaft Position Actuator Circuit / Open (Bank 1)Read about code...
Intake Camshaft Position Timing - Over-Advanced (Bank 1)Read about code...
Intake Camshaft Position Timing - Over-Retarded (Bank 1)Read about code...
Exhaust Camshaft Position Actuator Circuit / Open (Bank 1)Read about code...
Exhaust Camshaft Position Timing - Over-Advanced (Bank 1)Read about code...
Crankshaft Position Camshaft Position Correlation Bank 1 Sensor ARead about code...