n_Tu and n_Ab failed
Switch off ignition; Disconnect electronics from transmission; Connect terminal tester between TCU and transmission; Switch on ignition; Measure voltage between pin 10 (EF2) and pin 15 (AU2), nominal value: 9 V; Measure voltage between pin 2 (EF1) and pin 6 (AU1), nominal value: 9 V; Switch off ignition; Disconnect electronics; Measure resistance between pin 15 (AU2) and ground / housing, nominal value: > 10 Mohm; Measure resistance between pin 10 (EF2) and ground / housing, nominal value: > 10 Mohm; Measure resistance between pin 6 (AU1) and ground / housing, nominal value: > 10 Mohm; Measure resistance between pin 2 (EF1) and ground / housing, nominal value: > 10 Mohm; If you find deviations from the nominal value, check wiring, component, and TCU;
What you'll see
No driver-visible symptom recorded.
System reaction
Deactivate Neutral Standby;Deactivate Automatic Idle Shift;Open lock up clutch;Switch off retarder;Switch off engine brake (If available);;;;;;;;EFP restrictions;short time slip of lock up clutch locks;No reverse gear possible;Change only into a certain high gear if Neutral -> D is pressed on the Shift Console;
Diagnostic depth
Read-back voltage outside permitted value Speed drops to 0 rpm in a few milliseconds Output stage of TCU (TREX) reports hardware failure; Normal mode
Increased fuel consumption; Limited driving operation; Reduced driving performance; Reduced retarder braking performance;;