Mazda 6 Service Manual: No.9 abnormal shifting

No.8 does not shift to fourth gear (4gr)

No.10 frequent shifting

Other materials:

Mazda 6 Service Manual: Intermittent concern troubleshooting
  Vibration Method 1. If malfunction occurs or becomes worse while driving on a rough road or when engine is vibrating, perform the steps below. Note There are several reasons vehicle or engine vibration could cause an electrical malfunction. Some of the things to check for are: ...

Mazda 6 Service Manual: Starting procedure for on-board diagnostic test mode
Note All DTCs displayed in the on-board diagnostic test mode should be entered in the Audio Repair Order Form. 1. Turn the ignition switch to the ACC or ON position. 2. First press the POWER button, then simultaneously press the AM button and TAPE/MD button for 2 seconds or more. N ...