n_Ab, n_Tu, and n_Mot 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: 5 V; Measure voltage between pin 2 (EF1) and pin 6 (AU1), nominal value: 5 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; Check signal source of engine speed; 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;Open lock up clutch;Switch off engine brake (If available);;;;;;;;
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
Retarder is no longer available;;