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 Posted: Fri Nov 17, 2017 9:18 am |
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Joined: Dec 09, 2014
Posts: 28
Trade Rating: 0
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Peugeot 206 sport 1.1 HFX (2005) 82k miles.
This has been a bit of a project car that I've been working on in my spare time and hasn't been driven much in the last couple of years. Have replaced brakes, headgasket to cure oil leak, fully serviced and have just replaced the entire exhaust system including cat and both lambda sensors but I'm still getting error code P0170.
This code shows up as a pending fault code, and sometimes P0131 will also show as pending. It will not go into closed loop while the code is pending with a message on my scanner saying "open loop due to detected system fault (bank 1 or both). The exhaust system was in a bad way and also had a broken stud on the manifold to cat (well 2 broken studs after another snapped trying remove it) so I have replaced the manifold studs, gaskets and entire exhaust system including cat and for completeness fitted two new NTK upstream & downstream direct fit lambdas.
If I clear the code, the next start up will start normal and idle as it should and once warmed up will go into closed loop but as soon as it goes closed loop the revs at idle start to hunt up & down from near stall to around 900rpm, the O2 voltages don't switch and stay high at 1v with the fuel trim excessively high and after a few moments will set the MIL light with code P0170. If I restart the car the P0170 code moves from confirmed code to pending code and won't go into closed loop. I've thoroughly checked the inlet side of things for any leaks, cracks or splits and temporarily blanked off the servo & vacuum outlets on the manifold to eliminate any leaks in the pipework but made no difference.
Although both O2 sensors are new, what I have noticed is if I clear the fault code and try again but with the downstream post cat O2 sensor unplugged, the car starts and runs great and goes into closed loop with the pre cat O2 switching as it should and fuel trims spot on maintaining a steady 0% with no error codes reported or MIL. As soon as I plug back in the rear O2 it runs like crap again with the error code P0170. At the moment I'm going to leave the rear O2 disconnected as it runs fine with no error codes or MIL but would like to get to the bottom of this if anyone could shed any light.
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Posted: Fri Nov 17, 2017 5:03 pm |
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Joined: Jun 19, 2010
Posts: 1600
Trade Rating: +4
Location: South Bucks
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NTK?
If they are anything like the one I fitted to my Alfa years ago, they are your problem .. they are the wrong ohm rating .. you need Bosch parts!
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| Down to just the 1.4 HDi. Cayman Green 2.0i CC sold. | |
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Posted: Fri Nov 17, 2017 6:06 pm |
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Joined: Dec 09, 2014
Posts: 28
Trade Rating: 0
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Cheers. I'm aware of the problems of spiked coil/ecu from using NGK plugs and have fitted bosch plugs but thought NTK lambdas were a decent brand. The main front one seems to be doing its job when the rear one is disconnected. I didn't think the rear one had any influence on fuel trims and was there just to measure the performance of the cat. Will have to look into this in more detail as the error code was still showing before I changed the exhaust and O2's.
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Posted: Fri Nov 24, 2017 6:49 pm |
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Joined: Dec 09, 2014
Posts: 28
Trade Rating: 0
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Well I think I may have got to the bottom of this. What was confusing me is that the front o2 worked perfect when the rear was unplugged, but with the rear plugged in the front o2 remained at 1v and wouldn't switch and threw the fuel trim out. Before going through the hassle of checking all the wiring I first checked the fuses in the engine bay and re-seated all the connectors in there. Connected the rear o2 and started up and got it to closed loop and it now works perfect with both o2's doing what they should and fuel trim maintaining a steady 0%. The only thing I did was check and jiggle the fuses and unplug and reconnect the connectors in the fuse box so I can only think it must have been a dodgey connection.
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Posted: Fri Nov 24, 2017 11:47 pm |
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Joined: Jun 19, 2010
Posts: 1600
Trade Rating: +4
Location: South Bucks
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NTK is a reputable brand ... they are just the wrong ohm rating for many cars.
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| Down to just the 1.4 HDi. Cayman Green 2.0i CC sold. | |
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