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Post Cat o2 Sensors / Check engine light

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Hi all


I've had an intermittent CEL which has been diagnosed by my local Indy as as both rear o2 sensors. He suggested genuine senors are about 150-160/each, so potentially a fairly expensive job for something that should be straightforward.


I was considering getting a Carnewal exhaust (although not until the Summer), but now I'm wondering whether it's worth doing this at the same time/instead.Might be a silly question, but does the Carnewal exhaust still need/use the post-cat sensors?


Assuming I still need the sensors, I've seen Bosch ones for about £60. I'm assuming those will be decent? (I'm ignoring the £19 ones from ECP!). 



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47 minutes ago, extanker said:

doubtful that 2 sensors fail at the same time 


True, I might have misheard him. When we looked at the readings yesterday it was the right hand one that had the lowest readings, and the other side was just about ok I think.


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I get a CEL most months, normally after being stuck in slow traffic. it is always bank 2 cat warm up threshold exceeded. this is most likely a failing secondary lambda sensor, the one after the primary cat. I have a bluetoothed OBD scanner plugged in to the OBD port under the glovebox, that sends realtime data to my IPhone, I can use this to read and reset fault codes. Porsches do not store codes after clearing, unlike BMWs for example that then shut down the ecu once a factory preset limit is reached, My issue has been going on for well over a year and a half and whilst irritating, that's all it is and it does not affect engine performance or economy. ( ive never left the CEL go on for more than a week though).

Once Ive finished building my new exhaust with no secondary cats, I will probably replace the sensors. The fault might just go away once the cats are gone, without having to replace any sensors. as I understand it a partially choked cat will cause lambda sensor faults.

I believe that Carnewal system still uses all 4 sensors but has no secondary cats.

hope this helps Owain

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