Mod Description
These sensors measure the air/fuel mixture ratio and adjust the engine parameters. If either of these are faulty you can have an engine light on, poor running or bad mpg.Mod Details
PremiumNo Difficulty
Mod ID193
CreditEvilution
Cost££80 each
For
Linkhttps://evilution.co.uk/mod/451-lambda-sensors.htm Copy to ClipboardEuro 4 Exhausts
The 451 has 2 lambda sensors. The upstream sensor 1 is located in the exhaust manifold over on the right.
The downstream lambda sensor 2 is located in the middle of the exhaust can.
Follow the wiring to the connections and disconnect before undoing the sensors.
These can both be removed using a 22mm spanner and they spin out in an anticlockwise direction. It is always a good idea to spray them with PlusGas before removal to free them a bit. Also, a dab of copper grease can save them from seizing up next time. You can get special lambda sensor removal tools that are a socket, so you have more points of contact, but it has a split to accommodate the wiring. Click HERE for a link.
Alternatively, disconnect the connector and slide a 22mm ring spanner over the wiring to the lambda sensor. This is an option for both sensors on the Euro 4 exhaust.
On refitting, retighten the sensors to 40Nm if you have the correct tools. If not, just make sure it is tight, you don’t need to swing on the spanner though.
Sensor Part Number
A0045425318 is the part number that smart give for both sensors. So they should be interchangeable with the same connectors.
Euro 5 Exhaust
The Euro 5 setup is a little bit more complicated but the lambda sensor positions are the same.
The upstream sensor is over the to right and can be removed with either a lambda sensor socket or a 22mm ring spanner. However, the downstream sensor has a collar that really restricts access so ideally you’ll need the special 22mm lambda sensor socket.
Click HERE for a link.
Sensor Part Number
Non Turbo
Upstream – A 0055429818
Downstream – A 0045420718
Turbo
Upstream – A 0065422018
Downstream – A 0085428218
Sensor Bank Position Number
Apart from very early 600cc fortwos, all other petrol fortwos have 2 lambda sensors. Bank 1, sensor 1 and bank 1, sensor 2.
Normally, sensor 1 is in the upstream position (nearest the engine) and sensor 2 is the downstream sensor (furthest from the engine).
The downstream sensor is usually in the catalytic convertor can. The upstream sensor is either in the turbo or the exhaust manifold.
Be careful with generic error code readers because they don’t always give out the correct data.
As I said earlier, the upstream sensor should be 1 and the downstream sensor should be 2.
However some OBD readers will label the upstream sensor as 0 and the downstream sensor as 1.
If you want to be 100% sure, disconnect both sensors and see if your code reader brings up error codes for 1 and 2 or 0 and 1.