2020 Mercedes Benz Truck ML 350 Technical Service Bulletin # LI91-40_P-050718 Date: 120405
Restraints - Great Effort To Pull Out Front Seat Belt
Driver or front passenger seat belt can only be pulled out with great effort.
Topic number LI91.40-P-050718
Version 1
Design group 91.40 Seat belts, emergency tensioning retractors
Date 04-05-2012
Validity Model series 164 and model series 251 as of production date 06.2009 (code 800) and model series 221 as of production date 09.2009.
Reason for change
Complaint:
Driver or front passenger seat belt can only be pulled out with great effort.
Cause:
During the seat belt adjustment sequence after buckling up (belt slack elimination) the control unit A76 (left front reversible emergency tensioning
retractor) or A76/1 (right front reversible emergency tensioning retractor) detects an undervoltage. The undervoltage can occur briefly during the
starting procedure.
The undervoltage causes the belt slack elimination process to abort before it is complete. The drive unit of the reversible reel tensioner remains
engaged.
Remedy:
Pull out the seat belt with greater effort. This causes the drive of the reversible reel tensioner to disengage mechanically.
Do not replace the seat belt!
If the undervoltage occurs due to the engine start procedure, the problem can be avoided by starting the engine first and then putting on the seat belt.
2020 Mercedes Benz Truck ML 350 4MATIC (164.186) V6-3.5L (272.967) Page 66
On customer request the "belt adjustment" function can be deactivated using the multifunction buttons on the steering wheel. See operator's manual
"Switching seat belt adjustment on and off".
For BR 221 as of production date 09/2009 (code 800) up to 09/2010 (code 801) with old software release (part no. A2214420269, read out via quick
test), new software (part no. A2219026302, read out via quick test) is required. The new software can be flashed with DVD 05/2011 (Xentry) with
add-on 1857 or with DVD 07/2011(Xentry) with add-on 1877.
For BR 221 as of production date 09/2010 (code 801), BR164, BR 251 as of production date 06/2009 (code 800), the new software is available as of
DVD11/2010 (Xentry). The new software is installed by repeating initial startup of control units A76 (left front reversible emergency tensioning
retractor) or A76/1 (right front reversible emergency tensioning retractor).
Software releases:
Model series 221 - old software A2214420369 - new software A2219026402
Model series 251 - old software A2519020700 - new software A2519021800
Model series 164 - old software A164420069 or A1649023000 - new software A1649025600
Note:
The part numbers of the software can be read out via quick test / control unit log.
Symptoms
Control unit/fault code
2020 Mercedes Benz Truck ML 350 4MATIC (164.186) V6-3.5L (272.967) Page 67
