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Thread: Exhaust Emission Light.

  
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    Exhaust Emission Light.

    Hi all,

    I have a 2002 astra 1.6, and 2 weeks ago the emissions light came on. I took it to a local garage and they carried out a diagnostic on it, and it came up with the fault code of P0420, which relates to the cat, or the H052 sensor?

    They tested, and both the sensors were working fine, they also put the car through a emissions test and it passed fine, so they reset the light on the dash and it was sorted, but friday just gone, I had been out for a drive with a friend and it came back on again

    The mechanic said that there could be carbon getting on the ends of the sensors? If thats not the case has anyone ever had this problem and could point out what it is?

    Thanks.
    Astra GSi 03 in Arden Blue

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    Follow jam On Twitter
    Have it check out again for emmissions and if your emmission are inline with guidelines then replace the sensor itself. The sensor is in a very hostile environment +300degrees C, water, wind, fast heating periods ect so I would expect them to occasionally go faulty.

    Also look for a hole in the manifold too. A good sign of a hole in the manifold is a ticking sound when cold which goes away when hot. This can also cause it.

    jam

    Edit: As the code points at your second H02S (after CAT) make sure that the plug is firmly connected from the sensor to the car. After having my exhaust done it became detached and gave me the same codes as you have. Once I plugged it back in all was good. (you'll find the sensor on the top of the exhaust pipe at the back of the engine bay.
    Its a jam thing

    Haec credam a deo pio, a deo justo, a deo scito?



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    Are the sensors expensive to replace? I will have a look at the conncetion on both the sensors.

    Thanks.
    Astra GSi 03 in Arden Blue

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    dont worry they arent that expensive if u source them from a trusted independent dealer but dont worry about that now

    remove both sensors and clean the ceramic ends with petrol or carb cleaner - spray some WD40 on the other end (ie the electrical connector end)

    disconnect battery for 30mins or so to clear any stored codes and reset the ECU (thus turning off the warning light) **remember to have your stereo code at hand if u still have the original head unit - if u dont have the code then unplug the 2 plugs on the ECU for a few mins - this will clear the ECU in the same way but retain power to the stereo therefore no need to input a code** OR see method below for code reader

    Hopefully that will be it...

    if of course the light reappears then first of all check its for the same reason (do the pedal test instead of paying for a diagnostic check - details here

    if its the same fault code then maybe the only cure is replacing the sensor(s)

    personally though Id spend £20 on a code reader (such as this)and whenever the light appears just plug it into the OBD port under the handbrake - press RESET and the light goes off - providing the emissions are correct and its running sweet (as u say it is) then why pay to replace the sensors!! (thats my personal opinion of course)

    HTH

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    Cheers Bandit, Ill give the cleaning method a try sometime over the weekend, as im too ill at the moment
    Astra GSi 03 in Arden Blue

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    Bumping this. It came back on again 2 weeks later. I have just done the pedal test you suggested, Bandit. I got P0420, which is the same as the last time.

    Think I'll have to clean the lambda sensor under the car this week or sometime at the weekend.

    If I clean them both, should the light on the dash go away straight away? Or will I need to get reset it myself by disconnecting the battery?

    Thanks.
    Astra GSi 03 in Arden Blue

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    P0420 Catalyst System Efficiency Below Threshold (Bank 1)

    usually the cat itself iirc

    but defo clean both lambdas and see if it improves

    if u can get to the ECU on your car - just unplug the 2 big plugs for 5mins to reset and faults - this retains power to the HU unlike disc the battery

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    TBH Bandit, I have absolutly no idea where the ECU is :| Will it show you in a haynes manual?
    Astra GSi 03 in Arden Blue

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    This pic shows it on the side of the block but i know in some cases its located to the right of the battery

    if u wanna disc the battery instead do that - it just means u dont have to faff around with stereo codes if ur using the original HU

    if not, then just disc the battery before u do the work - clean all the lambdas and when u finished it should be reset


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    I wouldn't attempt to clean the sensors, you risk contaminating them. The code P0420 refers to the catalyst itself - it usually means it's reached the end of its life. I assume the emissions test you refer to is the standarrd MOT emission test which bears no relation to the EuroIII rolling road emissions test, upon which the diagnostic thresholds are set to determine a failed catalyst.
    mking

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