Changing the Lambda sensor

If you’re experiencing poor fuel economy in your 106 GTi, one of the primary culprits is the Lambda (or Oxygen) sensor malfunctioning. The Lambda sensor reads how much oxygen remains in the exhaust after the combustion process. This tells the ECU whether to inject more or less fuel into the cylinders. If the sensor is not working correctly, the ECU often injects too much fuel, harming the fuel economy and not doing much good to the Catalytic Convertor. To find out if your 106 could be suffering poor economy, use the MPG calculator here. Around 35mpg is usually the average returned by a GTi.

Replacing the Lambda is a bit of an awkward job as it is located behind the cast iron exhaust manifold which does not make it easy to get a spanner on the sensor. The oil filter also hinders the process. To solve this problem I bought a lambda sensor spanner, designed to hinge and make getting a grip on the sensor easier.

First remove the plug on top of the gearbox. To get to the loom plug, you have to remove the Airbox. This comes out easily enough, just disconnect the hose from the throttle body and cold air feed and lift the box out. This should expose the lambda sensor plug on top of the gearbox with a red tab. Pull the red tab out and remove the plug from the loom.. Now get the car up in the air and secured on Axle stands. Get underneath the front end, and you will see above the oil filter and behind the manifold the lambda is visible. Try placing the spanner on the plug. Hopefully after some trying (and swearing) you will get a grip on the lambda and you can undo it with some force. Withdraw the sensor and pull through the wire. You may find you have to remove the oil filter to gain enough access. In this instance you may as well carry out an oil change (see how to do an Oil change here) as you will lose a lot of oil from the filter anyway.

I removed the filter, and even then there wasn’t enough room to get a spanner on the lambda. So I ended up unbolting the lower part of the manifold and dropping it down. This gave enough room to manouver the spanner and remove the sensor.
The replacement sensor I bought was part number 238 038 717 available from any good Bosch dealer and some stockists on ebay. The Peugeot part number for reference is 1429 N2

In true Haynes style, fitting the new part is the reverse of removal but take car not to touch the end of the sensor as it is very delicate.

Leave a Reply

Your email address will not be published. Required fields are marked *