Dorman 904-377 Diesel Exhaust Fluid (DEF) Heater

Dorman 904-377 DEF Heater for Mercedes-Benz

This Dorman Diesel Exhaust Fluid (DEF) Heater is a specific-fit replacement for select Mercedes-Benz diesel applications, including GL350 and GL320 models. Dorman OE FIX engineering updates the factory design to address a common failure point caused by fluid intrusion, helping restore DEF system function with a more durable layout.

Key Features

• Specific-fit DEF heater for select Mercedes-Benz vehicles
• OE FIX design modifies the original heater layout to address fluid intrusion concerns
• Plastic housing with black finish
• Female inlet and outlet fittings
• Level sensor type: resistor
• Electrical connector quantity: 2
• Mounting hardware included
• Part number: 904-377

Detailed Description

Dorman 904-377 is a Diesel Exhaust Fluid heater built for direct replacement on select Mercedes-Benz diesel models. It is engineered around the factory DEF heater failure mode described by the manufacturer, where fluid intrusion can lead to premature breakdown. This OE FIX solution updates the OEM design to improve reliability while maintaining the correct fit and connection points for the application. It is a specific-fit component with plastic housing, female inlet and outlet fittings, and a resistor-style level sensor. This part cross-references URO 1644711275 for the same application. Use this DEF heater when servicing Mercedes-Benz GL350 and GL320 vehicles that require a replacement heater assembly.

Vehicle Fitment

• Fits 2015-2016 Mercedes-Benz GL350, N/A, w/166.825 Body Code
• Fits 2010-2012 Mercedes-Benz GL350, N/A, w/166.825 Body Code
• Fits 2007-2009 Mercedes-Benz GL320, N/A

Common Issues This Part Can Address

• DEF heater failure from fluid intrusion
• Loss of DEF heating function in cold conditions
• DEF system fault codes related to heater performance
• Improper DEF tank temperature control
• Replacement needs on Mercedes-Benz GL350 and GL320 diesel models

Installation Notes and Tips

Verify the vehicle’s body code and model year before installation. Confirm connector style, inlet and outlet fitment, and sensor configuration against the original unit. Mounting hardware is included, and the part is intended for specific applications rather than universal use. Always inspect the DEF tank and related wiring for contamination or damage before installing the new heater.

Quality Assurance

Dorman OE FIX parts are engineered to address known failure points in original equipment designs while preserving application-specific fitment. Part number 904-377 is built for select Mercedes-Benz GL350 and GL320 diesel applications and follows the OE-style connection and mounting layout required for proper service replacement.