How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Kevin Your Own Question
Kevin, UK Car Mechanic
Category: UK Car
Satisfied Customers: 2088
Experience:  Diagnostic technician at vw /audi specialist
Type Your UK Car Question Here...
Kevin is online now
A new question is answered every 9 seconds

I've had anti pollution fault come up on my 1.4 Peugeotreg.

Customer Question

Hi I've had anti pollution fault come up on my 1.4 Peugeot(###) ###-####reg. Had fault codes read which said it was rear lambda sensor. I've changed this and fault light went off only to reappear two days later. Car is running absolutely fine though, any ideas?
Submitted: 2 years ago.
Category: UK Car
Expert:  Kevin replied 2 years ago.

Hi my name is***** will try and help you first do you know the exact code that is stored?

Customer: replied 2 years ago.
Expert:  Kevin replied 2 years ago.

Ok do you have any exhaust leaks at all and was lambda a correct fit or a universal lambda?

Customer: replied 2 years ago.
No exhaust leaks and peugeot sensor fitt
Expert:  Kevin replied 2 years ago.

Ok do you have any machine to read live data ?

Customer: replied 2 years ago.
No i dont
Expert:  Kevin replied 2 years ago.

This really needs to be done next the code is basically saying that the voltage before the cat is low on the live data you will be able to see this and see what engine is doing at the time also an emissions test will help to see exactly what fuelling system is doing have you visually checked the wiring from connector ?

Customer: replied 2 years ago.
Everything is as it should be. Just cant understand why the fault has come back up
Expert:  Kevin replied 2 years ago.

At some point the car must have seen low voltage for a period of time on multiply occasions to have registered the fault code . We used data recorders and reset system then the recorder plugs into 16 pin diagnostic plug and records all the data whilst customer drives car they then return car to us when light returns and we can analyse data and capture the moment of failure

Customer: replied 2 years ago.
Right ok so basically its just gonna have to go back on diagnostics. I wondered if the cat was maybe on its last legs would that report up separately or could it cause it to report as rear lambda sensor?
Expert:  Kevin replied 2 years ago.

It's highly unlikely that it's your cat as the front lambda is what the fault code if referring too and the front lambda is there for fuel control ( to make sure car doesn't run to rich or too lean ) and the rear lambda is there to give the air value after the cat to show the difference between the two lambdas . This shows that the cat is doing it's job

Customer: replied 2 years ago.
Now I am confused that fault code said rear lambda sensor but you its front?
Expert:  Kevin replied 2 years ago.

You are correct I misread code I'm my look up it refers to rear lambda that could suggest that you have a cat starting to age