If there is a BCM. My previous 1995 GMC C1500 had a PCM and the automatic transmission was controlled by mechanical linkage to a hydraulic computer in the transmission along with shift solenoids from the PCM. It also had "throttle-body injection" with two injectors replacing the carburetor. The OBD 1 system would switch to "open loop control" with preprogrammed injection in the event of a malfunction which would make the thing challenging to drive until you fixed the problem. So very simple compared to the multitude of computers and control systems in use today.

A nice feature on that system was that you could put a paperclip between two pins on the diagnostic port and it would blink out the trouble codes on the SES light.