had the lambda sensor replaced yesterday, code P0156 sensor 2, bank 2, drove it today and the engine light has come back on, garage are saying it could be a wiring issue or the cat? any ideas, thanks, its a 2006 1.6 ti-vct

Need to check whether it's the same code first.  If it is, I'd suspect a wiring fault, the cat shouldn't cause that particular code.

same code as before, just found out the code was still pending when i got the car back, so wasnt cleared afterwards, 

13 minutes ago, steplce74 said:

same code as before, just found out the code was still pending when i got the car back, so wasnt cleared afterwards, 

Have you cleared it now then?  Hopefully it won't return if so.

thanks, so far so good, 

engine light is back on, ive had no end of electrical problems, it had an after market cat put on it before i bought the car, then a bad misfire which ended up being a wiring issue, 

I think this is right but I might be wrong. I think the sensor creates the voltage itself from the reaction of the gas on the precious metal in the sensor. So with the engine running you should be able to check the voltage output from the sensor when the engine is running even when the sensor is unplugged from the loom. You need the correct colour wires of course. Then with sensor plugged in use obd code reader and software to see the voltage.  Big difference?   Of course this would be no good if  it was the sensor before the cat as it uses the voltage signal to adjust the fuelling many times per second.  But the sensor after the cat just takes a reading to see if it thinks the cat is effective, it does not cause any fuelling adjustments. At least that’s how I understand it.  So everyone feel free to say if they agree or if I’m talking rubbish

Has the right sensor been replaced? On the 1.6 ti vct there's 2 upstream and 2 downstream from what I remember. 

when my cat was replaced before i got the car it only has a single bank on the cat

Yours must be a late 2006 vehicle then. Change over was from around sept/Oct 2006. But the code is for bank 2 sensor 2 . Non existent on your cat now. 

 

mine is march 2006, got a feeling the garage put a cheaper one on instead of the double one

4 hours ago, steplce74 said:

mine is march 2006, got a feeling the garage put a cheaper one on instead of the double one

Sounds like it. I would check if there are spare plug connectors next to the ones you already have. 

it's defo a single cat 

What about any spare connectors? Probably find an image so you can see where to look. 

This is all I could find , gives an idea on where they are. Connectors in pairs. 

its only got the one connector on the cat

1 hour ago, steplce74 said:

its only got the one connector on the cat

Yeah, I know that, I mean are there spare connectors 

no spare ones

 

Well that's me done. I can't offer any other solutions. Is a bit weird. 

is there anyone in kent who could have a look for me as i have spent loads on it and dont want to replace the cat as its only 3 years old, thanks

How does a mechanic diagnose the P0156 code ?

An OBD-II scanner is used to record any trouble codes that have been stored by the power control module (PCM).

Real-time data from the oxygen sensor on the OBD-II scanner is examined to determine if the oxygen sensor is functioning properly.

They will be able to draw a conclusion by noting if the oxygen sensor transitions from low voltage to high voltage as it should.

Using the OBD-II scanner, they will see real-time data for the fuel injectors to ensure they are working properly.

The oxygen sensor wiring will be inspected for shorts, breaks, or exposed wires.

The engine will be checked for escaping air.

This could be an indication of vacuum leaks or broken vacuum lines, then the exhaust will be inspected for holes.

Common mistakes when diagnosing the P0156 code :

The most common mistake when diagnosing the P0156 trouble code is automatically replacing the oxygen sensor without inspecting any other components.

The oxygen sensor isn't always the problem, and replacing it doesn't always fix the problem.

Consideration should be given to the condition of the wiring, exhaust, vacuum lines, intake and fuel injectors.

 

You should look for a leak in the exhaust, from the manifold to the catalyst, change the gaskets, put some special exhaust paste and tighten with new bolts/nuts

had a look myself and the cat i have only has 2 sensors, the one i should have has 4, i do have some spare connectors, sorry iantt

On 9/16/2022 at 9:40 AM, steplce74 said:

no spare ones

 

 

24 minutes ago, steplce74 said:

had a look myself and the cat i have only has 2 sensors, the one i should have has 4, i do have some spare connectors, sorry iantt

🤣🤣, So you do or don't have spare connectors. So if you do have spare then you need the correct cat system and 4 sensors 

it was put on before i got the car, trusted the car dealers, 4 years later it needs replacing, been quoted 600 for a  replacement but no warranty as it would be genuine otherwise over 1000 and i have no end of electric issues, the car runs well just has a engine light on

yeah there are spare connectors