Question

I got the code U2105 on my 2002 Saturn 3.0L 6 Cyl, the engine starts but go off

Answer 1

U2105 Loss communication with ECM

The vehicle should start even with U2105, when you get this code condition it can be with the TCM (Transmission control moduel) the vehicle will shift hard, this is where there is no communication with the TCM, if the vehicle just cranks and no start or start and dies this would be with the BCM (body control module) alarms installed with the vehicle are mostly the cause for this code condition.or the anti theft being active Check 3 area to resolve this issue, in the engine fuse relay box replace the main relay and check fuse listed as B+ which is a 10 amp fuse.

Comments

ECM to TCM, DVC (direct voltage current) to input ,or output, speed sensors,of transmission GM's 4t45e. 12 volts missing from TCM, from ECM. ***Programming error in ECM***. REmap ECM, try again look for voltage connection,to both sensors mentioned  on Windows 10. to OBD2 connector.

Answer 2

U2105 Code - Lost Communications with Engine Control Module
Read more: https://www.autocodes.com/u2105.html