Selective Ride cannot send DTC info over the serial data line. You have to use flash code diagnostics for SRC.
The most any scan tester can do is ground the appropriate termainal on the DLC such that the SRC controller will send data, so buying a scanner to work on SRC is a waste of money.
You can duplicate that function by turning the key on not starting the engine. Ground diagnostic link connector (DLC) terminal C of the '89-'93, 12-pin connector, or terminal 3 of the '94/'95, 16-pin connector, then observe the flashing Service Ride light to get the fault codes.
For more diagnostic info on SRC,
see this story on the CAC site