Nissan Repair: Automatic g/box not shifting, comm error, nissan serena

Question
dear Calvin,
My nissan serena 2001 is not changing gears  and is giving faulty code po600. Mech has tried to cancel code but it still comes buck.At times it respones only for a short while then back to just one gear and reverse.
Changed oil which was clean still the same.
What should I do?
Best regards
Anshel

Answer
Hi Anshel
Code PO600 is a comm error. This may be the ECU. Clear the code and turn ignition off. Turn the ignition back on and observe the check engine light. It should go off after a few seconds. If not then the ECU is bad
Hope this helps
Aloha
Calvin