Undershoot in Auto modeDT507/508 encountered the above symptom at few stations. Event record analysis show Average Brake Cyclinder Pressure Bogie 1 & 2 abnormal for 3507 & 3508. Please investigate and follow up further, thanks. ~~~~~ 507/508 Undershoot in Auto mode at few stations. Event record analysis show Average Brake Cyclinder Pressure Bogie 1 & 2 abnormal for 3507 & 3508.  507/508 found having under-run fault from ER records. Found ACU having intermittent high BC pressure on both DT cars. Replaced both ACU & function test both 3507/3508 - OK. ACU S/N :        OLD                 NEW 3507 :         1037-019           1934-083 3508 :         9948-045-08        1048-032  Chan SW/Hanafi 43840