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A4/S4/RS4 B7 2005-2008

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Old 28th May 2018, 02:35 PM
HPsauce HPsauce is offline
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Location: Chilterns, almost over HS2!
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Default Lambda sensor problem, possible MOT fail - thoughts please

My son's S4 again...…
His Engine Management Light came on a while back (not that long after a service at Audi )and being unaware of the upcoming MOT changes I told him it wasn't a problem, but I'd scan it sometime.

Did that a few weeks ago, cleared the 3 errors, the light went out and so far, hasn't returned. But scanning it today 2 of the errors are there so maybe it's just a matter of time?

Initial 3 errors, cleared 3 weeks ago:
19711 - Oxygen (Lambda) Sensor B1 S1; Heating Circuit P3255 - 001 - Regulation at Upper Limit - Intermittent - MIL ON
18683 - Oxygen (Lambda) Sensor B1 S1: Negative Lead P2251 - 004 - Open Circuit - Intermittent
18675 - Oxygen (Lambda) Sensor B1 S1 P2243 - 004 - Reference Voltage Open Circuit - Intermittent
Readiness: 0000 0000
Errors found and cleared today:
19711 - Oxygen (Lambda) Sensor B1 S1; Heating Circuit P3255 - 001 - Regulation at Upper Limit - Intermittent
18675 - Oxygen (Lambda) Sensor B1 S1 P2243 - 004 - Reference Voltage Open Circuit - Intermittent
Readiness: 0000 0000

Note the 18683 error hasn't returned. We ran the car after clearing the errors and none returned so I guess they are genuinely intermittent.
My thoughts are:
1. Is the sensor failing or could it be a wiring fault?
2. What level/frequency of which error cause the MIL to come on?
3. If it does come on presumably that will now be an automatic MOT fail if not cleared before the test?
4. Could the 18683 error be a red herring related in any way to the work done by Audi on the power steering disaster in April; all completed before I did these scans?
2003 D2 FL S8. Irish Green Pearl/Beige. Solar sunroof, auto-dim mirrors, electric rear seat functions and extended leather. Ski hatch retrofit. Aftermarket reversing camera. DVB-T and XCarlink now removed as redundant.
2016 Volvo V40 T5 Cross Country (4WD) with ALL the toys including adaptive cruise etc. etc. Osmium Grey with Blonde/Charcoal leather interior. Polestar performance "optimisation". (A much rarer model than a D2 S8 by the way!) Oh, and a brand new engine at just under 30,000 miles on the factory one!
Finally: gone, but not forgotten.....
1998 D2 PF S8. Agate Grey/Platinum. Every option (I think) except electric rear seats, Tiptronic steering wheel, ski hatch, towbar & dimming door mirrors.
e.g. Cruise control, NavPlus/TV, Bose, GSM, Xenons, Solar roof, Parking sensors, Alcantara/leather everywhere of course. (internal dimming mirror added later)
1998 (very early) Ford Focus 1.8 Zetec; ABS/TCS, Heated screen/mirrors, Aircon. Added Auto-dim mirror, Leather seats, Trip computer, Cruise control, OEM Ford SatNav with CD changer.
And before that a lot of Rover 800s, a few oddities, a lovely Triumph Dolomite 1850HL with Overdrive and way back in my schooldays an Austin Seven aka Mini 850!

Last edited by HPsauce; 28th May 2018 at 02:39 PM.
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Old 28th May 2018, 09:08 PM
27litres's Avatar
27litres 27litres is offline
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Join Date: Jan 2014
Location: Belgrave, Australia
Posts: 803

Open circuit and heating failures are pretty common when O2's get a bit of age on them.
I know the steering rack is in the same general vicinity, just depends whether or not they disturb the wires getting it in or out.

For the sake of 100 in parts, it may be prudent to replace them.
Check if the plug is the same as the D2 (bit over 1" x " with round ends), as Bosch no longer supply the early plug as a direct replacement. I buy NTK now.


2001 Audi S8 - Brilliant Black with Black interior, C5 RS6 rims (whenever I actually put them on...), Solar Sunroof, Tinted side and rear glass, RNS-D, Grom, Bose, clunky old phone in arm rest!
2002 Audi S8 - Project
Replacement head coming arrived thanks to MJ
Silver with Black interior. All features as the '01, with the 'S' mode auto shifter. Dodgey rear tint (need to find a way to get rid of that).
2009 Volvo XC90 V8 R Design
- has a louder more obnoxious exhaust than the S8, sounds great! Love this thing - Q7 was double the price, and certainly not double the car!

1997 Audi A4
- Hamilton's Club Sport, Achat Grey (will miss the old girl)
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