P0191 Fault Code

Long Description

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.

Some of the most commonly searched manufacturers along with this code include Ford, Toyota, and Volkswagen.

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.

Be sure to look out for other fault codes as well. These will typically be codes like P0170, P0172, and others.

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.

Fixes

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.

Seriousness

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.