Here are the command codes for 8192 BAUD ECM/PCM (Most copied from Internet?)
Mode 0 – Clear All ALDL Modes
Mode 1 – Data Frames (There are many different message frames)
Mode 2 – Request 64 Bytes of Memory
Mode 3 – Request 6 Particular Bytes of Memory
Mode 4 – Control Mode
Mode 5 – Enter Download Mode (GM Development)
Mode 6 – Address Of Routine to Execute (GM Development)
Mode 7 – Broadcast Mode (GM Development)
Mode 8 – Disable Bus Chatter
Mode 9 – Enable Bus Chatter
Mode 10 – Clear Malfunction Error Codes

The most commonly used modes are Mode 1, 2, 4, 8, 9 and 10

Mode 1 is used for getting the operating parameters out of the ECM, in mode 1 there are also many different messages. Each message is a fixed length and contains different parameters such as RPM, coolant temp, vehicle speed, etc etc. Each message contains different items for different logging/diagnostic tasks. Some messages contain engine params, some transmission (auto only) and others for when GM connect tech-1 to calibrate the unit.
This is what you normally see "Mode 1 Message 0" in TunerPro. This is directly from ALDL.ds file

Mode 2 is used to upload the binary (the contents of the memcal EPROM) from the ECM to a PC.
This needs to be built into TunerPro, If you change out chip to EEPROM then you could upload tune from ALDL port like WinFlash does for LT1 PCM. It erases flash memory then uploads your new bin

Mode 4 is useful to fault find sensors. It allows you to substitute or slew sensor values. For instance, it is possible to override the coolant sensor and substitute it with a different value to see what effect it has. Or you can slew (or offset) the temperature by a few degrees.
I have no idea?

Mode 8 and 9 allows you to temporarily disable the ECM/PCM from attempting to communicate with devices on the bus. If you don’t issue a mode 9 (enable chatter) frame after a few seconds the ECM will resume its normal communications.
Mode 8 is what I needed to silence communications from my HVAC/EBCM unit at 0xEA

Mode 10 clears all the stored malfunction codes. If you are having problems and experience a CEL then a malfunction code will be stored in the ECMs RAM. It is possible to erase the codes by disconnecting the battery but this also clears other learning data so a mode 10 ALDL frame can be issued.
See how to do this with TunerPro:
http://www.gearhead-efi.com/Fuel-Inj...on-Error-Codes

8192 baud is a bi-directional. READ DATA ON PIN "M" OF ALDL CONNECTOR. Send commands in and get data out!

160 baud and is a uni-directional (read only) data link. READ DATA ON PIN "E" OF ALDL CONNECTOR
So Clear Codes will not work on 160 BAUD ECMs. It has no Commands, just 160 BAUD out.