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Audi A3 and A4 B7: How to Replace Engine Coolant Temperature (ECT) Sensor

A bad coolant temperature sensor in the Audi A3 or A4 B7 could cause your car's temperature gauge to read the wrong temperature. Read on to learn how to replace it.

By Bassem Girgis - March 23, 2016
Contributors: Audiforums.com

This article applies to the Audi A3 and A4 B7.

A bad coolant temperature sensor in the Audi A3 or A4 B7 can cause your car to use more fuel than usual. You can always detect a bad coolant temperature sensor by reading the engine diagnostic code, but you can also detect it by the increase in fuel consumption, the sudden change in the temperature gauge, or by seeing black smoke coming out of the exhaust. You will most likely see a check engine light on the dashboard when your sensor is faulty. This guide will show you how to replace your coolant temperature sensor.

Audi A3 and A4 B7 How to Replace Engine Coolant Temperature (ECT) Sensor

Materials Needed

  • Flat head screwdriver
  • New O-ring

Step 1 – Remove engine cover

The engine cover is held in place by a few clips. Gently pull it up to remove it from the engine.

AUDI A3 A4 ECT ENGINE COOLANT TEMPERATURE SENSOR REMOVE REPLACE HOW TO
Figure 1. Remove engine cover.

Step 2 – Remove coolant temperature sensor

The temperature sensor is in a tight area, behind the engine, closer to the passenger side. It has an electrical connection connected to it, so remove that by inserting your flat head screwdriver in the small opening to push on the tab, then pull it away from the sensor. Pull the sensor out slowly, and note that some coolant will drip, so be prepared.

AUDI A3 A4 ECT ENGINE COOLANT TEMPERATURE SENSOR REMOVE REPLACE HOW TO
Figure 2. Coolant temperature sensor.

Step 3 – Install new sensor

Be sure to install a new O-ring on the new sensor, then install the sensor back in its place. You will have to get a visual before putting your hand through; the area is small, so it's either your hand or your vision. Install the electrical connector by pushing it into the sensor.

AUDI A3 A4 ECT ENGINE COOLANT TEMPERATURE SENSOR REMOVE REPLACE HOW TO
Figure 3. Coolant temperature sensor.

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