Hi, I'm new to this so I hope I'm putting this in the correct place, I have a 2001 octavia vrs engine code auq and the cat has been stolen, they also thought it would be a good idea to cut the wiring to the lambda sensors off up high so I have no sensor plugs. The new sensors just have straight colours so I have no idea what colours from the ecu go to what pins on the sensors. If anyone can help me it would be hugely appreciated. My only other option is to buy a new engine loom

I should be able to help you tomorrow morning.  Remind me by bumping the thread if I seem to have forgotten. 

Pre-cat is a wideband oxygen sensor with a 6-way connector

Pin 1 Green wire from ECU pin 70

Pin 2 Black wire from ECU pin 71

Pin 3 Blu/red heater 12V 

Pin 4 White from ECU pin 5

Pin 5 Grey/White from ECU pin51

Pin 6 Grey/red from ECU pin 52

 

Post cat is a normal 4-pin connector

Pin 1 blue/red, heater 12V

Pin 2 grey/yellow, heater control  from ECU pin 63

Pin 3 grey/white from ECU pin 68

Pin 4 grey/red from ECU pin 69

 

If you buy the right sensors and match up the pin numbers it should all work, I hope.

 

 

OK. Thank you very much for all your help, it's very much appreciated 

Hello Breezy_Pete,

 

Would you also have similar wiring information regarding the first lambda to ecu of a skoda octavia 1U2 engine code BFQ from 2004?
 

Best regards

@Treb_Kavon can you please share the VIN, so I can pick the most relevant diagram by build date?

Edited 18 December, 20241 yr by Breezy_Pete

I found this: TMBCX41U542913056

It's this I think:

 

Thanks for you prompt reply! May I ask slight help of interpreting the diagram? The upper grey area is the ecu and the lower grey is the lambda sensor. In the lambda sensor the left side depicts the sensor itself and the right side is the lambda heater. In this there would be 5 wires to the lambda sensor, but in my car in the connector there are only 4 wires. Or am i reading the diagram incorrectly? Here is an image of the lambda connector that is fitted on the car:

The second (nearer tailpipe) sensor should only have 4 wires, maybe you are looking at that?

The diagram I posted is for the one nearest the engine, which is a wideband type, these always have more than four wires, I believe.

Hmm...I will need to check the sensors again. I was pretty sure the 4 pin wires were leading to the place near the engine and the 5/6 pin to the place near the tail. Either i looked incorrectly or the lambdas are installed swapped (is that physically possible?). The OBD reader was referring to O2 sensor 1 bank 1 circuit.

 

Going back to the diagram. Are those color codes from german?
gn = green
ge = yellow
bl/ge = blue/yellow
sw = black
ws = white

 

And the number following the slashes (example: T81a/34) are the pin numbers right?

4 minutes ago, Treb_Kavon said:

Going back to the diagram. Are those color codes from german?
gn = green
ge = yellow
bl/ge = blue/yellow
sw = black
ws = white

 

And the number following the slashes (example: T81a/34) are the pin numbers right?

Yes and yes.

 

 

Colours going to sensor 2 ( bank 1 sensor 2) are:

 

From fuse to sensor pin 1 - blue/yellow

From ECU pin 5 to sensor pin 2 black (thicker one)

From ECU pin 35 to sensor pin 3 green

From ECU pin 16 to sensor pin 4 black (thinner one)

Connections 1 and 2 at the sensor are the heater.

Thanks again! I will take a look when I have the car again. Just to confirm "the second lambda (nearer tailpipe) sensor should only have 4 wires" is a firm fact and there are no reasons why it should be the other way around?

6 minutes ago, Treb_Kavon said:

is a firm fact and there are no reasons why it should be the other way around?

Yes.

Hello again, you were right. The lambda with 5 wires is the upstream one. I was checking the wrong one. Do you know what kind of readings i should get with a multimeter when testing both connector pins resistance?

Between the heater pins is probably a few Ohms, but may vary with temperature so try with cold system. I don't think any other meaningful measurement can be done on the sensor part.

 

Heater wires 3 and 4 give a resistance with lambda disconnected is 5.4 ohms. Wires 2 and 6 give 74 ohms

Edited 21 December, 20241 yr by Treb_Kavon

What problem are you actually trying to solve?

Please see images added.

I am not sure what readings should i get. S8me sources say lambda heater resistance should be somewhere between 10 and 20 ohms. And if not it could mean a short circuit. Maybe thatswhy the signal voltage is over 0.9 volts? That would mean that the lambda sensor needs to be changed. This would be an easier fix than ecu or ecu wiring issues...

The sensors voltage reading remains over 0.9 volts even when the lambda is disconnected

Wideband sensors are not easy to test,  I believe.  Try replacement. Do you want a part number?

Sure thing. Although this problem we had before and changed the lambda 1 year ago. The engine light was then off till summer when it lit up again.