Fault code P0093 – fuel system leak detected – large leak

Fault code P0093 is called “Fuel System Leak Detected – Large Leak” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0093

This diagnostic trouble code (DTC) is a generic code. Error P0093 is considered a generic code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

To extract maximum power from every drop of fuel, it must be atomized enough inside the cylinder to be ignited efficiently. This is why an internal combustion engine does not burn liquid fuel, but rather fuel vapor.

To achieve sufficient fuel ignition, most fuel injection systems operate at a moderate pressure of 2-5 atmospheres. Pressure and atomization combined with high intake and cylinder temperatures help the fuel evaporate even better. This provides better power output and fuel economy.

Diesel engines and some modern gasoline engines use a different form of fuel injection, injecting the fuel directly into the cylinder. In this case the fuel is injected in the compression stroke, when the pressure in the cylinder is close to its maximum. Therefore, the fuel injectors must operate at a much higher pressure.

A fuel pump mounted in the fuel tank supplies fuel to a mechanical fuel pump, usually mounted directly on the engine. The mechanical pump increases the pressure in the direct injection system. Most gasoline direct injection (GDI) systems operate at pressures up to 170 atmospheres. And diesel fuel injection systems are pressurized to over 270 atmospheres.

To properly measure fuel injection, the engine control module (ECM) closely monitors and adjusts the high-pressure system even between injector pulses.

If the controller detects an unexpected drop in pressure on the high pressure side of the fuel system. Anywhere between the mechanical fuel pump and the fuel injectors.

The control module sets a diagnostic trouble code (DTC) P0093, which means that a large fuel leak is detected in the fuel system. Also, the engine warning lamp (MIL), on the instrument panel, lights up after that.

Symptoms of vehicle malfunctions

The main signal that an error P0093 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

1. The “Check engine” control lamp on the control panel will light up (the code will be written in the memory as a fault).
2. The engine may start emergency mode and completely shut down.
3. Large loss of power under load.
4. The engine stalls or starts poorly.
5. Increased fuel consumption.
6. Fuel odor coming out from under the hood.
7. Decreased fuel pressure.

The error P0093 is quite serious, since its occurrence may cause problems with the engine and vehicle controllability. If this code is detected, it is recommended that you contact a qualified technician as soon as possible to diagnose and correct the error.

Factors that can cause this error code

The error code P0093 can mean that one or more of the following problems have occurred:

• Fuel injector malfunction.
• Leak in the fuel line.
• Worn or damaged hoses related to the fuel system.
• Faulty fuel pressure sensor.
• Loss of power at fuel pump due to failure.
• Short circuit in injectors wiring harness or engine control unit.
• Clogged fuel filter, resulting in reduced fuel line volume.
• Failure of fuel pressure regulator.
• Fuel pressure sensor is out of order.
• Sometimes the cause is faulty PCM module.

How to fix or reset OBD-2 code P0093

Some suggested steps for troubleshooting and fix the error code P0093:

1. Inspect injectors for leaks.
2. Check the fuel pressure.
3. Test the fuel pump.
4. Inspect the fuel lines.
5. Make sure the regulator on the fuel rail is working properly.
6. Pay attention to the fuel pressure sensor.

Diagnose and repair of problems

When the cause of the error, in this case P0093, lies on the surface and can be easily fixed, it is one thing. But sometimes it happens that the cause is very difficult to find, so let’s go over the most important places.

Fuel pressure as well as the fuel pump

Fuel pressure can be checked with a mechanical gauge attached to the fuel ramp. If the pressure is within factory specifications, there may be a faulty fuel pressure gauge giving false readings to the PCM/ECM.

If you can’t get to the test point with a pressure gauge, you can connect some fittings between the fuel lines and the fuel ramp. You can also use a diagnostic tool to check, which will show the results in real time.

Check the fuel pump for sufficient power by finding the wiring harness. Measure the battery voltage at the positive terminal of the fuel pump with a digital voltmeter.

If not enough power, test the wiring to the fuel pump. See if there is excessive resistance, loose wires, or faulty connections.

High pressure fuel system

Check all connectors and wiring harnesses. Make sure they are free of bent or twisted contacts or corrosion. Replace or repair if necessary.

Pay attention to the fuel injector driver (FID). If the driver or fuel injector has been replaced, the FID should run a re-learning program. Which sets it up for the high pressure pump and fuel injectors.

Inspect the system for fuel leaks, also check the oil level. If the oil level is higher than normal and smells like fuel, look for a fuel injector leak. Especially if you also have fuel correction malfunction codes or ignition skips.

If you can’t find any problems with the high-pressure fuel system. But you have other fuel system related trouble codes. Diagnose and correct them before returning to error P0093.

Fuel lines and regulator

Look for physical damage or kinks in the fuel lines that may be causing difficulties in the supply or return line. It may be necessary to remove the fuel filter to determine if it is clogged and needs to be replaced.

Fuel should flow freely in the direction of flow indicated by the arrow on the fuel filter. On some vehicles the filter is located at the inlet of the fuel pump itself, you will need to remove the module. To determine if there is a lot in the tank, which can also restrict the flow of fuel to the pump.

On vehicles equipped with a reverse fuel system, the regulator is usually located on the fuel rail itself. The fuel pressure regulator has a vacuum line that mechanically limits the fuel supply based on the amount of vacuum created by the engine.

Check for damaged or loose vacuum hoses to the regulator. If there is fuel in the vacuum hose, there may be an internal leak in the regulator, resulting in a loss of pressure.

On non-return systems, the fuel pressure regulator may be located inside the gas tank on the fuel pump module, and the fuel pump module assembly may need to be replaced.

Fuel pressure sensor

Check the fuel pressure sensor by removing the connector and checking the resistance at the terminals using a voltmeter. Resistance should be within factory specifications. Check the reference voltage to the fuel pressure sensor, it should be about 5 volts, depending on the vehicle.

If the voltage is not within specifications, inspect the wiring to determine if there is excessive resistance in the wire. It should be very low, close to 0 ohms. If resistance is present, a ground fault may have occurred and the wiring will need to be traced to locate the fault.

By performing a check on these points, you should be able to determine the problem of error P0093. And once determined, it should be easy to solve.

On which vehicles does this problem occur most frequently

Fault code P0093 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

• Citroen (C4, C5)
• Fiat (Ducato)
• Ford (Ranger)
• Hyundai (HD78)
• Isuzu (NPR75)
• Mazda (BT-50, MPV)
• Mitsubishi (L200, Pajero)
• Nissan (Cabstar, Navara, Pathfinder)
• Opel (Astra, Meriva)
• Peugeot (4007, 407, Boxer, Partner)
• Toyota (Avensis, Hilux, Land Cruiser, Prado, RAV4)
• GAZelle (Next)

Fault code P0093 can sometimes be found with other errors. The most common are the following: P0087, P0094, P1113, P1351, P3003.

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