OBD-II DTC · SAE J2012
U0679
Lost Communication With Transmission Fluid Pressure Sensor/Switch A
What U0679 means
U0679 is a standard SAE J2012 powertrain diagnostic trouble code with the defined meaning: Lost Communication With Transmission Fluid Pressure Sensor/Switch A. This is the OEM-agnostic definition; specific manufacturer interpretation may add detail (subsystem, bank, sensor location) but the core meaning is consistent across all OBD-II compliant vehicles since 1996.
Common symptoms when U0679 is active
Gearbox limp, harsh shifts, TCM communication MIL, ratio / solenoid / pressure DTCs.
Can this code be suppressed via ECU tuning?
Whether this code is safe to suppress depends on the underlying cause. Diagnose first, suppress only after confirming the mechanical issue is benign or rectified.
How to remove U0679 with Softechpro V5
Recommended service: DTC OFF (TCM) — limited use. Step-by-step workflow:
- Transmission DTCs usually require the actual TCM dump, not the engine ECU. Confirm the code is on the TCM side.
- Softechpro V5 supports DTC OFF on common TCM platforms (DSG, ZF, Mercedes 722.6 / 722.9, GM 6L80, BMW ZF8HP).
- Load TCM .bin, select DTC OFF + transmission DTC group, save, flash.
Softechpro V5 supports 1,400+ ECU firmwares across Bosch (EDC15, EDC16, EDC17, MD1, MG1, ME7, MED17), Siemens / Continental (SID, SIMOS, EMS), Delphi (DCM, DDC), and Magneti Marelli platforms.