There are two way for Data Logging:

1. Data Logging through stock DLC Data Link Connector. For more information, see DLC communication

2. Data Logging using ECUs inside serial connector (CN2/CN3) with a modified serial handler of ECU code

Stock OBD1 ECUs have datalogging capability built-in as part of the standard on-board diagnostics. However, the serial port operates at a baudrate which is not standard for PC serial ports. I can't remember offhand what baudrate it actually is, and PCs may be capable of using it, but most of us who do OBD1 datalogging use code based off of Doc's original datalogging code (which contained a bug).

Stock OBD1 and OBD0 ECUs have datalogging capability built-in as part of the standard on-board diagnostics OBD. However, the serial port operates at a baudrate which is not standard for PC serial ports. I can't remember offhand what baudrate it actually is, and PCs may be capable of using it, but most of us who do OBD1 datalogging use code based off of Doc's original datalogging code (which contained a bug).