Blue Coolant Temperature Sensor – 025-906-041A

Optimize your engine’s fuel mixture and ignition timing with the 025-906-041A Blue Coolant Temperature Sensor. This critical sensor, often referred to as the "Temp Sensor 2," provides real-time coolant temperature data to the Engine Control Unit (ECU) in fuel-injected Volkswagens. By monitoring engine heat, the ECU can adjust the fuel-to-air ratio—providing a "choke" effect for cold starts and leaning out the mixture as the engine reaches operating temperature.

This is a 2-pin, 20mm clip-in style sensor easily identified by its distinct blue color. Over time, these sensors can fail or drift in accuracy, causing symptoms such as hard starting when cold, poor fuel economy, or a "hunting" idle. Because the ECU relies heavily on this data for almost every aspect of engine management, replacing a suspect sensor is a standard first step in troubleshooting drivability issues.

Detailed Vehicle Compatibility

This sensor is used in a wide variety of water-cooled Volkswagen & Audi models with fuel injection (Digifant, Jetronic, etc.) continuously across these years:

Audi S6 (2.5L):

1995, 1996, 1997

VW Vanagon (2.1L):

1990, 1991

VW Passat (1.8L, 2.8L):

1993, 1994, 1995, 1996, 1997

VW Golf (1.8L, 2.8L):

1990, 1991, 1992, 1995, 1996, 1997, 1998

VW Jetta (1.8L. 2.8L):

1990, 1991, 1992, 1994, 1995, 1996, 1997, 1998, 1999

VW Cabriolet:

1990, 1991, 1992, 1993

VW Corrado (1.8L, 2.8L):

1990, 1991, 1992, 1994, 1995

VW EuroVan (2.5L, 2.8L):

1993, 1994, 1995, 1996, 1997

Product Highlights & Features

Accurate ECU Data: Specifically calibrated to provide the precise resistance-to-temperature curve required by factory VW fuel injection systems.
OEM Identification: The blue plastic housing ensures you are installing the correct sensor for the ECU, distinguishing it from the black or grey sensors used for dashboard gauges.
Easy Installation: Features a 20mm clip-in design that seats into the coolant flange with a simple plastic retaining clip and O-ring.
Prevents Rich Running: A fresh sensor ensures the engine doesn't stay in "cold start mode," which can save your catalytic converter and improve gas mileage.

Technical Specifications

Part Number: 025-906-041A
Connector Type: 2-Pin
Diameter: 20mm
Color: Blue
Sensor Type: NTC (Negative Temperature Coefficient)

Installation & Maintenance Tips

Replace the O-Ring: Always install a new rubber O-ring (N-903-168-02) and a fresh plastic retaining clip (032-121-142) when replacing this sensor. Reusing an old O-ring is a guaranteed way to develop a coolant leak.
Cold Engine Only: Never attempt to replace this sensor while the engine is hot. The cooling system is under pressure, and removing the clip will spray scalding coolant.
Clean the Flange: Before inserting the new sensor, use a clean rag to wipe out the inside of the coolant flange. Even a small piece of grit can prevent the O-ring from sealing properly.
Electrical Contact: Check the pins inside the wiring harness plug for green corrosion. If the plug is corroded, the ECU will receive a "false" high-resistance signal, making it think the engine is colder than it actually is.

025906041A

V107209091

V10-72-0909-1

025-906-041A VW/Audi Blue 2 Pin Coolant Temperature Sensor - Vanagon & Golf

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025-906-041A VW/Audi Blue 2 Pin Coolant Temperature Sensor - Vanagon & Golf

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