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Audi A6 C5: How to Replace Engine Coolant Temperature (ECT) Sensor

The engine coolant sensor is an important component in your Audi A6 C5; it's designed to give your car alerts when your car is overheating. Read on to learn how to replace it.

By Bassem Girgis - April 5, 2016

This article applies to the Audi A6 C5 (1998-2004).

The Audi A6 C5 is equipped with a lot of sensors, which are designed to detect any faulty components. The engine coolant temperature sensor is designed to alert you when the car is overheating. A faulty sensor can result in serious overheating problems. Replacing the engine coolant temperature sensor ensures you're aware of the correct temperature of your engine. This guide will show you how you can replace the sensor the quickest and easiest way. So if your engine is cool and you're ready, read on to learn how you can do this procedure on your own in the Audi A6 C5.

Audi A6 C5: How to Replace Engine Coolant Temperature (ECT) Sensor

Materials Needed

  • Phillips screwdriver
  • Flat head screwdriver

Step 1 – Remove top covers

First, remove the engine cover by removing the four Phillips screws holding it in place. Then remove the plastic cover on top of the air box. You can do so by just pulling it up, and it will come right off. Finally, remove the plastic cover connected to the fresh air scoop, again, by pulling it out and away.

  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 1. Remove engine cover.
  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 2. Remove air box cover.
  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 3. Remove fresh air scoop.

Step 2 – Remove MAF sensor

Remove the mass air flow sensor by just squeezing its plastic tab, then pulling it out. Move the wires away from the intake tube, because you will soon remove the intake tube.

AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
Figure 4. Remove MAF sensor.

Step 3 – Remove air box

To remove the air box, locate the four metal clamps around it, then unclamp them by pushing them down with your finger. Then, disconnect the intake tube from the side that's away from the air box, simply loosen the worm screw on it, then pull it off. Finally, remove the air hose that goes on the side of the air box; you can do so by turning it clockwise until it comes off. Pull the air box as a whole.

  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 5. Unclip four clips.
  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 6. Disconnect intake tube.
  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 7. Remove air hose.

Step 4 – Replace coolant temperature sensor

The sensor is located under the intake tube, and you will see it through the narrow space you have. It is held in place by a c-clip. Insert your flat head screwdriver, then push the clip to the side towards the windshield to open it. Try to put your hand in to catch the clip. Pull the sensor out, then disconnect its electrical harness by squeezing its plastic tab.

  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 8. Remove c-clip.
  • AUDI A4 A6 C5 C6 ECT ENGINE COOLANT TEMP TEMPERATURE SENSOR REMOVE REPLACE LOCATION CHANGE HOW TO
    Figure 9. Disconnect electrical harness.

Step 5 – Install components

Installation is the reverse of removal.

  • Connect the new sensor to the electrical harness, then install it in place and push the clip in.
  • Install air box, intake tube, and side air hose.
  • Install MAF sensor.
  • Install fresh air scoop, air box cover, and engine cover.

Featured Video: How to Remove and Replace Coolant Temp Sensor

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