FSi Lambda faults - Help needed

muggles

Member
I'm hoping a fellow FSi owner can help.

I've recently had a new Pre-cat Lambda sensor fitted - Bosch direct fit equivalent for P/N 047906262

Unfortunately I continue to have poor running, fluctuating idle, loss of power when cruising / accellerating intermittently.

Using VCDS

Group 032 Fuel Trims display 0 and 0 which doesn't seem right - this is after 200miles of runnign and surely there should be some fuel trim.
Group 031 1st Lambda value sits around 0.977 and 2nd Lambda value stays permanently at 1.0
Group 030 gives Lambda status values as 00111 for Bank1 S1 and 0100 for 2nd block ?Bank1 S2 -- please could someone read this block on their FSi and let me know what it gives

VCDS Scan shows the following codes:

16523 - Oxygen (Lambda) Sensor B1 S2: Response too Slow
P0139 - 35-00 - -
16518 - Oxygen (Lambda) Sensor B1 S1: No Activity
P0134 - 35-00 - -
17441 - Sensor for NOx (G295): Signal too Low
P1033 - 35-10 - - - Intermittent

These all recur after about 200miles when cleared.

All of these could be caused by an exhaust leak - althouhg nothing obvious and I've checked the EGR connecting pipe again (previously replaced) -unlit blowtorch doesn't affect revs

I'm trying to work out if the new Lambda sensor is in some way defective.

I've never replaced the Nox Sensor, and dont' know if a faulty Nox would cause the B1S2 error (as I can't work out which other sensor would correspond with B1 S2 . I dont' want to shell out £199 for a new NoX sensor if not needed.

I can clean connectors and refit to ensure not a poor connection.

Any other ideas welcome- I would appreciate readings for blocks 030 and 031 from a fellow owner to compare.

Thanks for all your help which over the years has been invaluable.
 
Hi,

Us FSI owners have to stick together!

Only got VCDS kit a couple of weeks ago and plugged it for the first time yesterday.
Managed to do an autoscan and buoyed up by my success I thought I would try and help you.

I really do not yet know what I am doing with VCDS and stumbled blindly in.
Hope this is what you want, if it's not tell me what to do.

vcds blocks 30 + 31.jpg

From memory which might be flawed...

In block 030 the first figure varied between 00111 and 00011, the second remain the same.
In block 031 the first figure oscillated between 0.98 and 1.016 with 1.000 being the most showed value, the second figure did not change at 1.000.

Hope it assists.

Andy

PS I have a second FSI I could I can do the same with if you think it will help.
 
Hi Andy.
Absolutely fantastic - thanks for taking the time to do this.

So my figures look the same other than the readiness codes in block 30 where the second figure of 00011 is different - this may be the problem, that a signal isn't generated from somewhere - what I'm not sure of is if this value is from the Front Pre-cat lambda sensor or the Post cat NoX sensor -

I wonder if unplugging the NoX from the box in the passenger footwell and rescanning would denonstrate this? I might give this a try and see if my values in Block 030 change.

If no difference I'm suspecting wiring problem on pre-cat lambda and will have to trace / test back to ECU.

If anyone else can help with interpreting the scan codes in the 1st post I'd be very grateful

Thanks,

Pete
 
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