OBD 1605
Nissan Altima OBD code 1605 P1605 NISSAN - Automatic Transmission Communication The 1605 code for your year Altima is either due to a weak battery or a bad AT control unit. Weak battery - Faulty Transmission Control Module (TCM) - Harness is open or shorted between TCM and Engine Control Module (ECM) - Poor circuit electrical connection between TCM and ECM Here is the steps to check the system out yourself. https://dl.dropboxusercontent.com/u/105565483/1d.pdf If the transmission seems to function fine,then it is more likely to be either a weak battery or an opened or shorted communication line between the ECM and the A/T control unit? Malfunction is detected when an incorrect signal from Transmission control module (TCM) is sent to Engine Control Module (ECM). I would start by clearing the code and see if it returns. If it does, I would check the battery and the charging system voltage before replacing a control unit or getting crazy about checking wiring. Thi...