P0240 repeatedtly showing up

Nkosi · Oct 1, 2012

But before you start blaming the catalyst and sensors. This has only started after a new exhaust was fitted along with a new lambda sensor to my 2001 51 plate 3 door 1.8i. after the first two resets from the garage I bought a cheaper scan tool (£25) and have reset the code around 5 times since the exhaust replacement which was done around 2 months ago.

Nodge68 · Oct 1, 2012

Post cat sensors can be a pain as the cat ages. You could wire in a Mil eliminater. That way the code shouldn't re-log!! If the exhaust wasn't an OE part it could be partially blocked reducing gas flow over the O2 sensor. Or the new O2sensor is faulty?

Nkosi · Oct 2, 2012

Thanks, I think it was an after market and not OEM exhaust the whole job to do the exhaust and fit the sensor was just over £300 including catalyst. So that could be the problem, in which case I have to live with resetting frequently or shell out for the more expensive OEM parts.

Nodge68 · Oct 2, 2012

Nkosi said:
Thanks, I think it was an after market and not OEM exhaust the whole job to do the exhaust and fit the sensor was just over £300 including catalyst. So that could be the problem, in which case I have to live with resetting frequently or shell out for the more expensive OEM parts.

If that included the cat then yes it's a cheap one!! The most annoying thing with having reset the Mil on a regular basis is it could come on whilst at it's Mot which would now be a fail!! I'd look into fitting a Mil eliminater!!

Diesel Do · Oct 2, 2012

Why was the cat replaced? Not sure about a mil eliminator isn't it like pretending it's not broken?

Nodge68 · Oct 2, 2012

Diesel Do said:
Why was the cat replaced? Not sure about a mil eliminator isn't it like pretending it's not broken?

Technically a Mil eliminater is pretending there is nothing wrong but if it's only the post cat sensor that is giving a fault it's nothing more than a silly EU reg that says a really strict emission requirement must be monitored and put a light on if the cat is'nt quite up to scratch!! I've had one in my MG ZS180 for years as the light comes on sometimes due to the sports cat but it flies through the Mot no problem!!

Diesel Do · Oct 2, 2012

Nodge68 said:
Technically a Mil eliminater is pretending there is nothing wrong but if it's only the post cat sensor that is giving a fault it's nothing more than a silly EU reg that says a really strict emission requirement must be monitored and put a light on if the cat is'nt quite up to scratch!! I've had one in my MG ZS180 for years as the light comes on sometimes due to the sports cat but it flies through the Mot no problem!!

I admit I know nothing about mil eliminators! What happens if it comes on for a completely different reason? Does that mean you're unaware of another possibly serious fault!

DD

Nodge68 · Oct 2, 2012

Diesel Do said:
I admit I know nothing about mil eliminators! What happens if it comes on for a completely different reason? Does that mean you're unaware of another possibly serious fault!

DD

Not at all. The Mil eliminater is simply soldered into the Post Cat O2 wiring under the seat so is undetectable. It's function is to fool the ecu that the Post cat sensor is seeing the correct O2 in the exhaust gas after the cat has converted it!! It is simply a monitor and has nothing do do with the way the engine runs or sees the other sensors!!

Diesel Do · Oct 2, 2012

Nodge68 said:
Not at all. The Mil eliminater is simply soldered into the Post Cat O2 wiring under the seat so is undetectable. It's function is to fool the ecu that the Post cat sensor is seeing the correct O2 in the exhaust gas after the cat has converted it!! It is simply a monitor and has nothing do do with the way the engine runs or sees the other sensors!!

Ah that makes a lot more sense!

Nodge68 · Oct 2, 2012

Diesel Do said:
Ah that makes a lot more sense!

Good!! The silly part is the Post Cat O2 sensor monitors the exhaust gas to such a fine control window that even a tiny leak in the pipe will put the Mil on even though the Mot analyzer would pass the cat!!

Diesel Do · Oct 2, 2012

Nodge68 said:
Good!! The silly part is the Post Cat O2 sensor monitors the exhaust gas to such a fine control window that even a tiny leak in the pipe will put the Mil on even though the Mot analyzer would pass the cat!!

Yeah I've had troubles in the past with them just never come across this before! Where do you get em from? does it just put out a no oxygen flatline to fool the ecu then?

Nodge68 · Oct 2, 2012

Diesel Do said:
Yeah I've had troubles in the past with them just never come across this before! Where do you get em from? does it just put out a no oxygen flatline to fool the ecu then?

They are easy enough to make and only require 2 passive consonants. A resistor and ceramic capacitor. It basically tricks the ecu into thinking the O2 sensor is working and the exhaust gas is in spec!! Because it's a post cat sensor it won't alter the mixture at all as that is controlled by the signal from the Pre-cat O2 sensor!! There is loads of info on the net about them!!

P0240 repeatedtly showing up

Nkosi

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