Advice Lambda/Exhaust Temp sensors

Eoin

Eoin

Registered User
Joined
Mar 15, 2015
Messages
71
Reaction score
8
Points
8
Location
Dublin
Hi,

I’ve a 2001 S3 AMK and have been getting the engine light on for the past while-after clearing the faults the light goes off for a while but comes back on again. VCDS is showing the attached faults. I’m assuming I need new exhaust temp sensor and post cat Lambda (Bosch) - unless I find loose connections? Thanks, Eoin
79b13a8c8501faffa477c92436e73b03.jpg
 
Sadly yes... those are typical signs of faulty sensors...

Brace yourself for the EGT one...

<tuffty/>
 
If you are handy with a soldering iron you may be able to sort the EGT sensor. Had exactly the same EGT issue on my TT. Very common and it can be sorted cheaply if you are lucky. If you can log the EGT readings and monitor them whilst you tap the case / wiggle the sensor wire you may see it intermittently goto 1100 degrees which is what it reads when the sensor is open circuit.
https://www.audi-sport.net/xf/threa...car-1-8-bar-and-building.319422/#post-3034296
 
  • Like
Reactions: Alex C and badger5
Thanks for the quick responses....I know now what I need to fix or replace.....Eoin
 
I got a chance to run some logs of the oxygen sensor and EGT sensor....EGT mainly showing normal temps but some random readings from time to time so I guess that confirms there is indeed a problem with the sensor. Oxygen sensor showing mostly approx 0.9 but also shows values as high as 1.991 and as low as 0.6 - again I guess these figures are out of range hence the error message on VCDS. Am I right is interpreting that these values support the original diagnosis that both sensors are faulty? thanks.
 
cruising temps on egt would be in the 700c range, egt protection as std kicks in at 920c
under boost stock lambda request is only 0.95, and on overrun injectors are turned off so full scale lean 1.99, not a fault, wont pop up a code as this is normal. 0.6x lambda is very very rich..

post up logs of a 3rd gear pull, showing blocks 001,003,031
 
Thanks for that; I have the logs from my earlier run for blocks 001, 031 & 112 - attached are extracts for 3rd gear pulls.....I'll do for another run for blocks 001, 003 and 031 when I get a chance. Is it possible that the problem with the EGT sensor is affecting the lambda figures? thanks again, Eoin
 

Attachments

  • 20190607 S3 Run LOG-01-112-031-002.pdf
    41.5 KB · Views: 167
If the EGT is playing up it will default to max value and over fuel (rich)

<tuffty/>
 
Thanks Tuffty, I’ll have a look at the sensor and wiring to see if there are any bad connections and replace if I need to. Audi are quoting €371 for a new one so will be looking for a secondhand one if I need to replace. Eoin
 
Eoin said:
Thanks for that; I have the logs from my earlier run for blocks 001, 031 & 112 - attached are extracts for 3rd gear pulls.....I'll do for another run for blocks 001, 003 and 031 when I get a chance. Is it possible that the problem with the EGT sensor is affecting the lambda figures? thanks again, Eoin
Click to expand...
hi
egt if >920c will influence lambda yes, it will fuel dump, which you will also see as a % figure as its adding.
On your log you have dropouts, so its definately goosed.
Point less doing much else until this is replaced
 
Thanks, a new sensor it is then. While idle earlier today I cleaned the connections for the sensor and took it for a run and logs/temps now look ok. However, I don’t trust it so will be on the lookout for a new sensor.
 
Hi, could anyone tell me the pitch thread for the egt sensor on my s3 8l, it never had the egt when I bought it it was just blanked off with a bolt but that’s fallen out so I just need the pitch thread to replace it please
 
You must log in or register to reply here.

Similar threads

Dani_B19
S3 eating lambda sensors... any advice?!
Replies
3
Views
581
Dani_B19
Dani_B19
Audi_A31.8T
Lambda sensors
Replies
8
Views
2K
Audi_A31.8T
Audi_A31.8T
AL_B
Lambda Sensors
Replies
17
Views
2K
recomdos
recomdos
Cheeks
Lambda/O2 sensors
Replies
3
Views
498
Cheeks
Cheeks
S
Lambda sensors fault
Replies
0
Views
902
s3 man
S
Top
Back