1. Verify that the joint shaft is not twisted or cracked.
2. Turn the joint shaft by hand and verify that the bearing rotates smoothly and freely.

Drive shaft
Joint shaft removal/installationMazda 6 Service Manual: Dtc c1955, c1956
Caution
When attaching the tester lead to the DSC HU/CM connector the SST
(49 G066 004) must be used.
Diagnostic procedure
...
Mazda 6 Service Manual: No.9 tcs off light stays on more than 4 seconds with ignition switch on
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while
doing the inspection to discover whether poor contact points are the cause
of any intermittent malfunction. If
there is a problem, check to make sure connectors, terminals and ...