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850 / S70 & V70 '96-'99 / C70 '97-'05 General Forum for the 850 and P80-platform 70-series models |
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Grrrrrrr. Lambda SensorsViews : 11470 Replies : 123Users Viewing This Thread : |
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Jan 17th, 2011, 22:37 | #11 |
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The only O2 sensor reading i can see on that print out is Bank 1 sensor 2 which is the sensor after the cat that one doesn't move much as it's reading the exhaust gas after the cat has filtered it, you need to know what the sensor before the cat (bank 1 sensor 1) is doing thats the one you've been playing with this is the one that controls the fueling and is the one that fluctuates constantly when the engine is warm up and idling can you bring that reading up on your scanner
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Jan 17th, 2011, 22:42 | #12 |
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Ah yes, totally correct! My bad!
Will have a play tomorrow at lunch and see what I can bring up. I'm sure I had a Bank 1 Sensor 1 there at one point! |
Jan 18th, 2011, 14:14 | #13 |
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Right - it seems either the software I have, or my ECU, don't support reading the front sensor through OBD/OBDII. Pics have been linked to so I dont have to faff about with resizing them etc - Just got back to work!
Screenshot of Supported PIDs according to OBD2007 After clearing the codes, restarting the engine, and idling for a few mins (with a bit of throttle usage while sat in "P" ...) Linky It was in and out of Closed Loop / Unused though. On the Dashboard view the Fuel/Air was around 14.something - couldnt tell exactly as its a sliding scale. There are a few other pics in the directory - http://brutalhosts.com/carparts/ A few are obvious and have nothing to do with this, but the ones to look at are named with proper names rather than IMAGxx etc. After driving back to work the car is running rough and is smoking again, but the managment light is currently off. I expect it will turn on while I drive home. I will reset the codes and pull the battery for an hour when I get home tonight and see how she takes it when I go for a drive later tonight. Any more thoughts dpbayly? (Other than sort my Avast out!) |
Jan 18th, 2011, 19:56 | #14 |
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OBDII often does not support the display of wideband O2 sensor activity, I think this is what you are seeing.
Basically the fault code you are seeing is triggered by a disparity between the front and rear sensors. So given the front one is correct part and new the balance of probability is the problem is either with the rear sensor or the CAT. I'd try disconnecting the rear sensor and see what happens. |
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Jan 18th, 2011, 20:07 | #15 |
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Thank you Chris! Can you advise what *should* happen if I disconnect the rear sensor please?
James |
Jan 18th, 2011, 20:22 | #16 |
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I'd expect a couple of fault codes for the rear sensor and CAT monitoring to be disabled.
But I'd also expect the front sensor to be in use to establish fuel trim. Note the system will only go to closed loop operation if the engine is up to temperature and the either at idle or cruise. |
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Jan 18th, 2011, 22:11 | #17 |
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do you have access your self or know anyone who would let you do an emission test at a MOT test station to see whats going on see what the lambda, CO and hydrocarbons are doing this could give you a clue whats going on.
normally the 2nd sensor (after cat) is there just to check the cat is working and doing its job and if its not it will flag up a fault with the ECU As for switching all the time between open and closed loop this is strange as it should run open loop (car runs off pre set fueling maps) while cold till warmed up then switch to closed loop (uses the O2 sensors for feed back and makes adjustments) a car will also normally run open loop when at WOT (wide open throttle) as well. You need to find out why it keeps switching constantly between open/close this could be a temp sensor also modern of O2 sensors have a heater circuit to bring the sensor up to operating temp quicker i don't know if this plays a part in when it switches if it does this could be a fault. |
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Jan 18th, 2011, 22:12 | #18 |
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If you disconnect the rear sensor it will instantly put the management light on
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Jan 19th, 2011, 09:44 | #19 |
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Cool, thank you both. Will get home at lunch and have a look at the rear sensor and try and unplug it while the laptop is hooked up.
Reset the codes and had the battery off for an hour last night, and although the light has come back on again the revs are almost rock solid on about 950. Edit - If the problem is with the rear sensor (wouldnt be surprised after the smoke and muck that was coming out of the exhaust for a few days!) is it possible to clean it, or is it a whole new sensor jobbie? Last edited by JamesV70R; Jan 19th, 2011 at 09:47. |
Jan 25th, 2011, 19:25 | #20 |
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Thread revival!!
Been hunting for all the possible and varied vacuum leaks possible after the car started running lumpy again - chugging and throwing foul smelling smoke out of the exhaust. Can't see any obvious leaks, but the small rubber pipe that comes off the intake just before the Turbo (Part of PCV i think?) has a small split in it where it attaches, so we chopped the split bit off, reattached, and it has made no difference, so its not that ... If anyone fancies grabbing a copy of that and marking a few places to look where any obvious problems with vacuum related things could be ... it would be appreciated. Slowly giving up on this car. Would be a shame to see her have to go to the great scrapyard in the sky, but I can't afford to keep looking for problems and replacing things - nor can I afford to go to local garage and say "Here is my chequebook, tell me whats wrong ... " |
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