Lambda Sensor Replacement (B1S2) and Wiring

An information post really - purely because even though posts refer to the wiring of the lambda sensor, I could only find information about the plug and I needed the socket. For any other poor souls stuck on a cold windy day at 6pm here is the information!

I bought a genuine (£105.91) B1S2 (post catalytic converter) lambda sensor for my 1.4 petrol Mk1 Classic Fabia. Thinking it would be easy to replace (apart from awkward access). How wrong I could be!

First things first - WRITE DOWN THE PIN NUMBERS (shown on the plug and socket terminals) AND THE COLOURS OF THE WIRES!!!

The socket needed replacing - obviously due to a change in the design. No problem, new socket included. Instructions state (in pictures) pull wires out old socket and push into new socket. Oh yeah! First secret - look in the end of the socket and you will see a purple bit. This is actually a locking clip that holds the pins in place. Use a flat headed screwdriver to slide this completely out the side of the socket. With care it will go. The same will be true on the new socket.

Second point: The wires have a rubber bung in the socket. This will simply slide out, but since it may (like mine) have been there for 10 years, it can be pretty stuck. I used a flat headed screwdriver to push the metal socket terminals out back out of the plug - pushing the wires with them.

Third point: The terminals are very fiddly to get into the new socket. If they are not perfectly aligned they will not go. When they do, it is relatively easy, although the rubber bungs can be a bit difficult to encourage in! Be careful to make sure the wire is in line with the pin, and make sure you can see, and reach, what you are doing. Good access is the key!

Finally, the actual wire colours. This is specific to my chassis number (well, that's what the dealer needed to find the correct colours since I was stupid and forgot to write them down).

Terminal ----- Socket (From ECU) ----- Plug (From Lambda sensor) ----- Function (don't quote me!)

1 ----- Blue, Red stripe ----- White ----- Heater

2 ----- Brown, White stripe ----- White ----- Heater

3 ----- Grey, White stripe ----- Grey ----- Earth OR Power

4 ----- Grey, Red stripe ----- Black ----- Signal

I simply hope the above information helps someone. If anyone feels the need to add, please do!

Alan