MembersPage/BMW M50 turbo LSU4

Support will reproduce the issue after .vemscfg is provided - the one actually in use, saved from VT. (and it's newest fw, or 1.2.38 or 1.2.31). Waiting for that, no further action until that.

See FileArea

Edit this page to include reference.
- related to WideBandNernstVoltageTooLow page, but actual stat of project specific .vemscfg file and notes must be written here.
- if there are several messages, "merge them" and only include the uptodate actual state (no copypaste of chronological junk)
NOTE: For non-nonsense constructive work, always use real PC or notebook, not tablet or Android or Iphone

NOTE: thematically organized project page is required for technical support

any email must contain the reference to thematically organized project page.
Required for technical support, otherwise optional.
page name starts with "MembersPage/..." and

Sending multiple emails without reference to thematically organized project page is a waste of time, and is not supported. (This important requirement has been neglected multiple times).

IMPORTANT: any request must include saved .vemscfg, otherwise neglected (no matter how much measurement or other info is included) - saved with VemsTune (after "update ini files from web") any fw older than 1.2.31 will not be reproduced or supported)

Any report or request MUST include:

VemsTune version
- confirmation that "update ini files from web" was done
saved vemscfg file (which actually includes:
- many useful information
- firmware version
  - if fw is older than 1.2.31 it will not be supported. Eg. if 1.1.96 works for you, it's good, but we don't recommend modifications without/before firmware upgrade; The HW is supported for 30 years, but at this time there is no support for 1.1.96 fw when there are 10+ years newer firmware versions

Officially the newest fw is supported => there will be no fix if the newest works perfectly

in practice fw 1.2.38 and 1.2.31 should also work for 99% of the setups
- and (if the setup does not require newer features of fw) we reproduce setups with 1.2.31 or 1.2.38 to help diagnosis. But there will be no fixes if newest fw works well for the required features (also, newest has most features)

Speculation - should not waste time without .vemscfg

After testing v3/4603 with 1.2.31 and 1.2.38 (with real LSU4 sensor) and found it working we suspect that problem at site can be: some extremely old (<1.2.31) firmware, or something is misconfiguration

and in any case the vemscfg saved with "update ini files from web" (needed even with newest VT, because improvements come via "update ini files from web", VT reinstall not needed if newest).

It might be something weird in the "pump" (voltage controllerd current source with protection/limit) circuit, perhaps even something intermittent that worked consistently for hours when we tested in lab but fails consistently after shipping

very rare, something related to software/configuration related is much more likely, especially that .vemscfg was not supplied - that would be step nr.1 in ANY support or investigation case.

Please fire an ECU order in webshop just to specify desired ECU specs (might be slightly different than old ECU; 6 IGBT-s is most practical because it supports 6 passive coils, or 6 active coils also, using 2 logiclevel ign + 4 stepper outputs)

choose "IBAN/pay later" option (no need to pay; we prepare a new ECU but not sending until the even the most basic .vemscfg is provided so we can verify that it's not something like using old firmware, especially 1.1.96)

https://vems.hu/vemstune/bugreports/reports.php?cmd=view&key=lcI14X

Link to the current vemscfg file

config 1.2.31

ini files updated from web

Update 13/07/2026:

New ECU received from VEMS

Tested the new ecu in the car and the issue has remained the same.

The WBO2 Nernst DC Target is still low, with both ECUs outputting ~175mV between pump- and nernst.

Created Google Doc with test (https://vems.hu/vemstune/bugreports/reports.php?cmd=view&key=h6BXfH) results and pictures of vemstune settings and wiring for testing. (Link below)

https://docs.google.com/document/d/1omz35HRyJOtAs9ZGqcWJtmqf9KgUv2p_ePh1mVulZuc/edit?usp=sharing

I have also tested all of these things on the hardware to eliminate any issues there:

-New LSU 4.2 O2 Sensor (Original suspected fault)

-Original ECU returned to VEMS for testing/ repair

-Brand new ECU sent by VEMS (23326)

-Tested normal O2 sensor wiring harness for high resistance and continuity between wires (check for damaged or shorting wires)

-Tested ECU with custom O2 sensor test harness (see document)

-Powered ecu directly from battery (eliminate power feed issues)

-Tested all ECU grounds for high resistance

With the issue repeating on the new ecu and having tested all the hardware I can only assume the issue must be with my config?