2005 c5 petrol error code P0420
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  1. #1
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    Default 2005 c5 petrol error code P0420

    Looking at buying a c5 from auction. Its a 2005, with 150k on the clock. Seems in great condition for its age. But has a fault coming up.

    P0420 - Powertrain Catalyst System Efficiency Below Threshold (Bank 1)

    Also, looks like the last service was done around 120k from the log book. But starts easy, sounds fine, no weird noises, suspension works.

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    Question, should I reconsider even its dirt cheap? Did the 2005 facelift have the AL4 (been an auction I can't test drive)? Anyway to check the gearbox is playing up without driving it?

  2. #2
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    Can you put Diagbox onto it and get the two oxygen sensor readings. It might be both are too similar, or one is cactus. The car is old enough to need a new one. Cheap fix.

    A more expensive possibility is that too much unburnt petrol has been there - from misfiring or retarded ignition in the past. It doesn't appear to be happening now. Give the cat a hard knock and listen for anything detached.

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    PS With that sort of servicing, it might be a spark plug not giving a complete burn.

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    Hi Gareth
    I guess you are using a generic scanner to read that fault code ! C5 are prone to that code ! It could be the car needs a new set of plugs and filters check over etc and then a good long hard run with 98 petrol. Then see what happens. But it will be OK anyway if that is the only problem.
    I would give it a go if it seems OK and the price is right.
    Jaahn

  5. #5
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    Yes, AL4 carried over in the petrol 4. Vin has RF? in it. Was RFN, but it changed in facelift cars.
    The facelift 2.2HDi (4HX) gained the 4HP20 instead and the V6 petrol the AM6 instead of the 4HP20.
    In 2006, the 4spd 2.2HDi was replaced with the AM6 6spd 2.0 (RHR) and 2.2TT (4HS) HDi versions.

  6. #6
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    Thanks for the replies!

    Quote Originally Posted by jaahn View Post
    Hi Gareth
    I guess you are using a generic scanner to read that fault code ! C5 are prone to that code ! It could be the car needs a new set of plugs and filters check over etc and then a good long hard run with 98 petrol. Then see what happens. But it will be OK anyway if that is the only problem.
    I would give it a go if it seems OK and the price is right.
    Jaahn
    Correct jaahn, generic scanner.

    Quote Originally Posted by David S View Post
    Yes, AL4 carried over in the petrol 4. Vin has RF? in it. Was RFN, but it changed in facelift cars.
    The facelift 2.2HDi (4HX) gained the 4HP20 instead and the V6 petrol the AM6 instead of the 4HP20.
    In 2006, the 4spd 2.2HDi was replaced with the AM6 6spd 2.0 (RHR) and 2.2TT (4HS) HDi versions.
    The VIN starts with VF7RCRFJF. VIN date says 10/06 but build date is 09/05, which one do I go off if 2006 was the cutoff?

    Quote Originally Posted by seasink View Post
    Can you put Diagbox onto it and get the two oxygen sensor readings. It might be both are too similar, or one is cactus. The car is old enough to need a new one. Cheap fix.

    A more expensive possibility is that too much unburnt petrol has been there - from misfiring or retarded ignition in the past. It doesn't appear to be happening now. Give the cat a hard knock and listen for anything detached.
    Only have a generic scanner, so there could be more faults lurking deeper?

  7. #7
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    The generic scanner will get any fault code logged. It won't usually be able to get sensor readings from the engine, and the cat converter status is determined by an oxygen (lambda) sensor at each end of it. Those signals can be affected by wiring faults also.

  8. #8
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    Quote Originally Posted by garethb View Post
    ... The VIN starts with VF7RCRFJF. VIN date says 10/06 but build date is 09/05, which one do I go off if 2006 was the cutoff?...
    RFJ means EW10 engine. My limited experience with these suggests the earlier RFN (also EW10) cars probably had a little more pickup. That is probably just down to emission issues affecting the software, but it can sometimes feel a bit flat off the mark especially if you alternate between this car and something more powerful. The manuals do feel more alive.

    That difference between build and compliance dates just means it had a birthday in the bond store, it wasn't shipped to a dealer before 10/06 and may not have even been registered until sometime in 2007. The European model year seems to still run September through to the following August, although that may vary. So the car in question would likely be regarded as a 2006 model year car being built in Sept 2005. The rego papers probably regard it as a 2006 model. The petrol cars did not change when the HDi offerings did in 2006.

    The RP (aka DAM or ORGA) number on the build sticker (or in Citroen Service) converts to the build day. When chasing parts for these cars, it is useful for looking at production changes or whether something will fit or not. The supposed year of the car is less useful as it could be mean more than one model. The letters after the RP number may tell you the factory. In some cases, the same change was made in different factories using the same components or assembly at a different time. So the change points are expressed slightly differently by also quoting the letters.
    Last edited by David S; 15th August 2017 at 10:10 PM.

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    According to my book, David, compression ratios differed, 11 against 10.8:1
    RFN is 100 kW @ 6000 rpm; 190 Nm @ 4000 rpm
    RFJ is 103 kW @ 6000 rpm; 200 Nm @ 4100 rpm.

  10. #10
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    Hi
    My point about the generic scanner is that Citroen, PSA, use different descriptions to the standard american code descriptions that you find on the web. Sometimes the Citroen description may be more indicative of the actual fault. However the standard faults will be shown on a generic scanner by law. However how the software interprets the available information is variable, that is why you have to go to the crap factory software for the full effect.
    I guess that this fault is common too as I believe PSA set a high standard to pass and as the cars get old it is hard to achieve, but still running OK.
    Jaahn

  11. #11
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    That can be so. There is no bank 1 or bank 2 distinction on this engine. The CitroŽn code is:
    P0420: Efficacitť du catalyseur insuffisante
    Last edited by seasink; 16th August 2017 at 10:45 AM.

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    Hi
    I see that the car referred to has a different cat to the early ones. The cat is built into the manifold in a chamber not in a seperate metal unit underneath. Not sure what that means for a replacement, does it have a replaceable cannister unit or what ?? Nothing shown on the parts list
    Jaahn2005 c5 petrol error code P0420-20170816_204119-1024x576-.jpg2005 c5 petrol error code P0420-20170816_223030.jpg
    Attached Thumbnails Attached Thumbnails 2005 c5 petrol error code P0420-20170816_222505-1024x576-.jpg  
    Last edited by jaahn; 16th August 2017 at 11:38 PM.

  13. #13
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    Hi Gareth
    Anything happen at the auction ?? I am all agog
    Jaahn

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