Possible Causes

WARNING: This page is about a different car, the 2002 Mazda 626 and 2001 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

Following items are possible causes for DTC P0755:

Shift solenoid "B" malfunction.
Open or short to ground or power in shift solenoid circuits between PCM and shift solenoid "B".
Damaged connectors or wiring harness between shift solenoid "B" and PCM.
PCM malfunction.