GMTech bernard appears to be offline. My name is Scott.
The ESC module is the computer for the ride control.
The 2004 tahoe has over 14 modules in it, the correct one needs to be scanned.
You will need to Scan the Electronic Suspension Control module for fault codes and post them for GMTech Bernard.
Yes, like Scott said, you should have the ESC (electronic suspenstion control) module checked for fault codes, that will help isolate the problem. Unfortunately, a generic OBD-II scantool won't read this module, it requires a high-end scan tool.
However, some things you can do without the scantool, is 1) make sure all of the height sensors are plugged in and the linkages are hooked up on both ends (one end on the sensor and the other end on the suspension.) There is one sensor per wheel. I see alot of the linkages pop off for no apparent reason.
Also, try unplugging each shock and plug back in several times. The front shocks plug into the threaded portion of the shock (connector up top) and I see corrosion issues cause high resistance. Sometimes unplugging and plugging back in several times restores proper connection.
You can also measure the resistance of all four shocks. Make sure both front shocks are similar in resistance and both rear shocks are similar in resistance.
If all of this checks out good, then you will have to have the ESC module scanned for codes to be able to dig deeper.
PLEASE let me know if I can be of further assistance!