P0177 OBD-II Trouble Code: Fuel Composition Sensor Circuit Range/Performance

P0177 code definition

Fuel Composition Sensor Circuit Range/Performance

What the P0177 code means

P0177 is a generic OBD-II code indicating that the diesel fuel sensor has detected water in the fuel filter, or the fuel composition sensor is out of its specification range.

What causes the P0177 code?

• The engine control module (ECM) receives input from the diesel fuel sensor that water is detected in the fuel, or the fuel composition sensor is not within specification range, and triggers the P0177 code

What are the symptoms of the P0177 code?

• The Water in Fuel illuminates on the instrument cluster
• The ECM sets code P0177 to memory and triggers the Check Engine Light

How does a mechanic diagnose the P0177 code?

• Scans codes and documents the freeze frame data, then clears the codes to verify code returns

• Drains off water in the fuel filter by opening the water drain valve on the fuel filter housing

• If the Water in the Fuel Light does not go out, removes the fuel filter and tests the sensor, replacing it if shorted or out of specification range for the vehicle being tested

• Clears codes and tests the system to see if the Water in Fuel Light goes out, and the P0177 code does not return

Common mistakes when diagnosing the P0177 code

Follow these simple guidelines to prevent misdiagnosis:

• Drain fuel from the filter until no more water is present. If excess water is still in the fuel sample, then the fuel in the tank may be contaminated with excessive water and would need to be drained and replaced.

How serious is the P0177 code?

• If excessive water is in the fuel then you will have engine starting and running issues.
• The engine may misfire, hesitate, and stall.

What repairs can fix the P0177 code?

• Draining off water in the fuel filter and clearing the Check Engine Light Codes
• Replacing a shorted water sensor
• Repairing the shorted or burned wiring or connections to the water sensor
• Replacing the fuel filter housing with sensor, and clearing the codes

Additional comments for consideration regarding the P0177 code

Not many manufactures use the code P0177, and the code is set in the computer memory to indicate the engine fuel has or had water in it.

Need help with a P0177 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.