In the past, when your car broke down, it would have to be towed to the mechanic, where they would spend ages diagnosing your vehicle, just to overcharge you.

Today, check engine light codes, like the P0193, make DIY diagnosis possible. Such codes allow you to pinpoint the system that is at fault, order the parts that you need, and be back on the road ASAP. However, knowing the trouble codes you have is not enough. 

This guide will walk you through the P0193 code. What it means, the causes, symptoms, and anything else you might need to know to tackle it head-on.

What is the P0193 Code, and What Does It Mean? 

The OBD-II system defines the trouble code as “Fuel Rail Pressure Sensor A Circuit High Input.” The code means the PCM has detected a higher than normal voltage coming from the fuel rail pressure sensor. Fuel pressure issues lead to such as stalling and cylinder misfires.

What Causes the P0193 Code?

Fuel rail sensor issues are often related to either an electrical problem with the harness or an issue somewhere else in the fuel delivery system. Here are some of the common causes:

• Failed fuel rail pressure sensor
• Wiring harness issues
• Clogged fuel system
• Damaged fuel pump

Failed Fuel Rail Pressure Sensor

Your fuel rail pressure sensor monitors the fuel pressure in the fuel rail and sends that information to the ECU. The ECU then uses that information to adjust fuel injection and ignition timing. Failure often leads to an increase in fuel pressure, which will cause the P0193 trouble code.

Wiring Harness Issues

Transmission of power, signal voltage, and grounding all happen in the wiring harness. Breaks are common at the sensor connector, but can also occur inside the wiring harness sheath. These breaks will cause the engine computer to log the P0193 fault code.

Clogged Fuel System

Modern vehicles use high-pressure fuel rails in smaller turbocharged engines to improve efficiency. This high fuel pressure increases the risk of introducing foreign particles into the system. Depending on the size of the debris, you could develop a bottleneck in the fuel delivery system, which will often cause a P0193 error. 

Damaged Fuel Pump

Your fuel pump supplies fuel to the injectors and, by proxy, maintains fuel pressure. A failed pump leads to a lack of pressure and the P0193 code. It’s a common misconception that fuel pumps either work or they don’t. In reality, a fuel pump can suffer an intermittent failure, which will cause issues with the fuel pressure in the system. 

What Causes High Fuel Rail Pressure?

A failed fuel pressure regulator and fuel line clogging are the primary causes of this issue. The fuel pressure regulator ensures the correct amount of fuel is flowing to the rail by diverting any excess fuel back to the fuel tank. If this system fails, the fuel will either leak from the regulator or it will let the fuel pass through. The latter of which causes an increase in fuel pressure.

What Are the Common Symptoms of P0193 Fault Code?

When you know the symptoms of a trouble code, you can narrow down the root cause and shorten diagnosis times. Being able to recognize the symptoms will also help you identify issues before they progress further and cause damage. Here are the common symptoms of the P0193 trouble code:

• Check engine light
• Reduced performance
• Poor starting behavior
• Black exhaust smoke

Check Engine Light

The check engine light is the number one sign of car trouble. Here, it doesn’t spell disaster and only illuminates. Fuel injection issues either cause your vehicle to run rich or lose power, both of which aren’t a safety,9 times out of 10.

Reduced Performance

A reduction in performance is a given when you have any fuel injection issues. It isn’t a negligible performance loss either. Jerky acceleration and lack of power when you depress the throttle fully are both potential signs of the P0193 code.

Poor Starting Behavior

This is similar to suffering reduced performance, only this time the symptom appears when you’re starting the car. If it is struggling on a cold start, stalling after it barely started, or stalling when the vehicle slows down, you probably have a P0193 code.

Black Exhaust Smoke

Black exhaust smoke is one of the common signs of a rich running condition. Most air intake and fuel injection issues will cause this to happen, so it doesn’t tell you much about the trouble code. However, it’s important to note it as it will bring you closer to diagnosing your issue.

How to Diagnose and Fix the Cause of P0193 Code 

Diagnosing the P0193 code means getting up close and personal with the fuel delivery system. However, the very first step in finding out what’s wrong with your car is to run a full scan of the vehicle using an OBD-II reader. 

OBD-II Reader

This is your method of identifying the P0193 trouble code. Just plug your scan tool into the OBD-II port and select the “scan for trouble codes” or whatever similar option is present on your particular scanner. This will give you all the relevant trouble codes for your issue.

Visual Inspection 

Inspecting your vehicle is a vital first step in diagnosing your P0193 code. We need to look for damage to the wiring harness and sensors first. Any external damage, corrosion, or exposed parts on either the fuel rail pressure sensor or harness are signs of failure. 

Now we need to look at the fuel lines and rail for any damage. These leaks almost always occur when the vehicle is on. So a sure-fire way of finding leaks is to start your vehicle with the rail connected. The fuel will either spurt from the rail itself or break in the fuel line.

Additionally, you should inspect your fuel filter, tank, and pump for any signs of external damage. Do not remove these components at this point as we will be conducting less invasive diagnostic techniques before we conduct more internal diagnoses.

Wiring Harness Test

Of course, ruling out external damage doesn’t mean that there is no internal damage to the harness or connector. The best way to test this is using a multimeter. Some OBD-II scan tools allow you to read sensor voltage, but that option is relegated to professional-grade scan tools.

For this test, your car should be in the “key on engine off state.” You should first check whether the harness itself is good by back probing the sensor connector. Take your red probe and contact it with the wire you want to test. Your black probe should make contact with the vehicle chassis for the ground. We don’t know whether the harness is shorted to the ground, so we don’t probe the ground wire with the black probe yet.

Your power (red), ground (black), and signal (blue) should read around 12V, 0V, and 5V, respectively.

Checking for Fuel Pressure

This is another non-invasive test that you can conduct to check whether your fuel pressure is correct. You need a fuel pressure gauge or vacuum tester for this test.

Connect your tester to the fuel system. A good connection point is near the Schrader valve on the fuel rail. If everything is alright, you should get around 30-60 PSI. Turbocharged vehicles return pressures closer to 60 PSI. Remember to always consult your owner’s manual for specific numbers.

Diagnosing the Fuel Rail Pressure Sensor

So you’ve ruled out harness damage, time to move on to the fuel rail pressure sensor. Conducting this test is exactly like the wiring harness test. However, here we want to test whether the voltage rises based on the engine state. When your vehicle is in the “key on engine off” state, it should read around 0-0.5V. When the engine is idling it will read around 1.5V and when applying throttle it should read around 4V.

These numbers differ between manufacturers, so it’s always helpful to check your owner’s manual for exact values. 

Diagnosing Fuel System Issues

Although fuel system issues aren’t uncommon, they often happen in older vehicles, or when you run into a particularly low-quality batch of fuel. First thing first, relieve the pressure from the fuel system. That way you’ll avoid excessive spillage. 

There are two ways of doing this; One is using the Schrader valve on your fuel rail. It’s a small screw-in valve designed to relieve pressure from the fuel system. Take your screwdriver and unscrew the valve slowly. If this is not possible, you can disconnect the fuel pump relay and run your vehicle until there is no gasoline in the system.

Once you’ve completed that, you can remove the fuel filter and pump for inspection. In case your car only features an in-tank fuel pump, you can skip the step above. Just remember that once you pop the gas tank open, you’re working in a fume-rich environment.

How to Fix a P0193 Code

Cleaning your fuel system will often quickly resolve this trouble code. There are dedicated fuel system cleaners that you can flush your rail and lines with. 

You can also clean the fuel rail pressure sensor contacts if you suspect that your issue is electrical in nature. The contacts often corrode and cleaning them will solve your P0193. If the sensor itself is fine, you’re probably looking at a clogged filter or a faulty fuel pump, both of which will most likely need a replacement. 

If you’ve replaced the fuel pump, make sure to prime the system by turning the key to the accessory position a few times. 

Does P0193 Clear Itself?

It’s always better to clear trouble codes with an OBD-II reader. However, if you have fixed the root cause of the problem, the code will clear itself within a drive cycle.

Is It OK to Drive With the P0193 Code?

If you have this code, chances are you have been driving with it for a while. Fuel injection issues can cause long-term damage to your engine. In the short term, you shouldn’t worry too much about driving with this trouble code.

Fix the P0193 With Quality Parts

The only way to make sure that your engine is getting all the fuel that it needs is to use quality replacement parts when fixing the P0193 code. 

Here at eEuroparts.com, we carry a wide range of genuine, OEM, and quality aftermarket parts for a variety of European makes and models. Head over to our shop and input your vehicle’s info into our navigation tool. That way you’ll gain access to the list of products that are a guaranteed fit for your car!