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 Posted: Mon Nov 14, 2011 5:23 am |
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Joined: Nov 14, 2011
Posts: 3
Trade Rating: 0
Location: UK
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Hi
I have a Peugeot 206 1.1lx (reg Nov 2001). A couple of weeks ago, after about 10mins of motorway driving I had the engine management light come on. There was no difference in the car performance. A friend of mine plugged in his ODB2 reader which gave a P0420 error code (catalyst efficiency below threshold bank1).
I will now check the exhaust system for leaks and check the O2 sensors and cat. Sounds like a faulty O2 sensor as the Cat is about 2 ½ years old, the rest of the exhaust system is 6 months old. It also passed a MOT a month ago so the emissions were in spec at that point.
Using the ODB2 reader we selected to erase the code but this failed. My question is why can’t we erase/reset the code. I would expect the code to reset whilst the car is not running but with ignition on. Ok the light may come back on when you start the engine, as I have not yet changed anything, but surely the code should reset.
I also have noticed that the ODB2 reader says the O2S, HO2S & Cat are ‘Not Ready’. Is this anything to do with the failure to reset?
Can anyone explain this? or tell me how to reset the engine light.
Many Thanks
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Posted: Mon Nov 14, 2011 5:59 am |
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Joined: Feb 07, 2010
Posts: 13077
Trade Rating: +65
Location: England
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It's not going to reset if you haven't fixed the fault is it? 
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Posted: Mon Nov 14, 2011 6:46 am |
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Joined: Nov 14, 2011
Posts: 3
Trade Rating: 0
Location: UK
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Lee. Forgive my ignorance but surely you should be able to erase codes using the ODB2. I was hoping to reset, then see if the error re-occurs. As it is a "below threshold" error I would expect the error to re-occur after the engine was at normal running temperature.
Is it possible that one of the O2 sensors have shorted? i.e. they are in a constant error condition thus stopping the code from being reset.
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Posted: Mon Nov 14, 2011 8:27 am |
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Joined: Feb 07, 2010
Posts: 13077
Trade Rating: +65
Location: England
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It will be a permanent error hence it not deleting.
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Posted: Sun Nov 20, 2011 12:50 pm |
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Joined: Oct 28, 2011
Posts: 4
Trade Rating: 0
Location: Cornwall
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Had this happen to me last night on the way back from the NEC bike show, engine light came on, cars performance was unchanged, temp/oil gauges all normal. When i got home i plugged my OBDII reader in and it showed the same fault code, mine cleared but would'not extinguish the engine management light. The error has cleared now so i just disconnected the battery for ten mins then reconnected it. EM light is now off - until i'm next on the motorway i guess!!
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Posted: Sun Nov 20, 2011 1:03 pm |
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Joined: Apr 09, 2011
Posts: 445
Trade Rating: +1
Location: letchworth
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i get this but im able to reset it and it comes back every 3 weeks
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| if it dont scuff the ruff it aint low enuf | |
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Posted: Mon Nov 21, 2011 4:13 am |
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Joined: Nov 14, 2011
Posts: 3
Trade Rating: 0
Location: UK
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Update:-
Because the problem seemed to point to the downstream O2 sensor or the Cat, I decided to first change the sensor. This proved almost impossible as the sensor was rusted in and I could not unscrew it. I ended up applying heat to remove it, which unfortunatly damaged the thread.
So I ended up with both a new sensor and and a new Cat. Fitted these and went for a run to get the car to normal running temperature. Note:- the engine light was still on. I then plugged my ODB2 reader back in and tested. It came back with no problems, so I then selected the erase feature. The ODB2 reader then said erase successful and the light then turned off.
I then gave the car a good run up the motorway. All ran fine with no sign of the engine management light.
I will proberly never know if it was the sensor or the Cat, but hopefully it's sorted now.
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