1999 Subruban 1500 LT Failed Emissions Test: Catalyst Not Ready EVAP Not Ready O2 Sens HTR Not Ready EGR Not Ready Fault Codes: No codes Present -------> Check Engine light is not on.

YOU DICNNECTED THE BATTERY BEFOR THE TEST THAT IS FOR SURE, NOW YOU MUST PERFROM A DRIVE CYCLE TO LET THE ENGINE CONTROL MODULE RUN THROUGH IT MANY CHECKS OF THE EMISSION SYSTEM

if you had reset the code[ or had a dead battery]you just cleared and reset all the vehicles evap / emissions systems it now has to recycle through to reset you wont have a check engine or mil unless computer finds a fault and on most vehicles it can be about 125 miles and usually the last to reset are the evap and the catalytic converter drive around and at around 125 mark go to an auto store and have vehicle scanned most offer this service for free or if you have one check your system for ready if not keep driving some more most states give you 10 days to retry so use that time to rack up miles -- and dont reset or clear codes before an inspection

One possible issue is a faulty thermostat. If the engine is not getting up to normal temp the emissions system will not go into closed loop.
I know its hot in Nevada now so thats just a suggestion.
The O2 sensors have heaters to make the exhaust gas hot quick so that the sensors can work.
Is the check engine light coming on - or is it just that the exhaust gas is not hot enough for the test equipment ?

The O2 heater is part of the O2 sensor itself. You would need to replace the oxygen sensor if the heater is an issue.

Diagnostic Test Code (DTC) P0501 "Vehicle Speed Sensor Range/Performance"
DESCRIPTION
The Wheel Speed Sensor (WSS) generates a waveform with a frequency according to the speed of the vehicle. The signal generated by the WSS informs the ECM not only if the vehicle speed is low or high but also is stopped the vehicle or not. The ECM uses this signal to control the fuel injection, ignition timing, transmission/transaxle shift scheduling and torque converter clutch scheduling. Also the WSS signal is used to detect rough road driving condition.

Whenever Your OBD readiness monitors cannot complete it is because there is a problem that is affecting fuel mixture, ignition timing, or any other fault that can affect the level of tailpipe emissions. Once these faults are repaired, then the codes must be ereased so that the monitors can run and "re-test" the system to check for the same, or any other faults. The goal is for all the monitors to run and change to "complete" without any fault codes present.

In your case, the wheel speed sensor fault needs to be diagnosed and repaired so that the monitors will complete. Also note that one incomplete monitor can prevent other monitors from running. In your case, the catalyst monitor cannot run because the O2 sensor monitor is not complete. The catalyst monitor can only run AFTER the O2 sensors have received a "clean bill of health" from the O2 sensor monitor. The wheel speed sensor problem is keeping the O2 sensors from being tested.....So the wheel speed sensor problem is pretty much causing the whole thing.

Here's the kicker...If the vehicle has been driven in this condition for a period of time, there may be damage to the catalytic converters. The computer does not know this yet because the catalyst monitor cannot run. So it is possible that you can fix the wheel speed sensor thing, the O2 sensor monitors will complete, then when the catalyst monitor runs it could set a "catalyst efficiency" code. Then you will have to replace your catalytic converter to fix that. I'm not saying that this WILL happen on your vehicle, I am just saying that it CAN happen so you will not be confused IF it DOES happen. I see this all the time, and I have had customers accuse me of doing something to their car so I could sell them a high-dollar catalytic converter. This is simply not the case...I had no way of knowing that the converter had a problem because when I first received the car, the catalyst monitor was incomplete and there was not catalyst code present at the time.

So the only way to do this is to correct ALL fault codes one at a time until all monitors are complete and no fault codes are present.

This is the heater side of the sensor. It has shorted out. You can replace it, but check for broken or melted wires (around the exhaust).

Drive the car for 2 miles non-stop and take it to smog inspection WITH OUT TURNING OFF THE CAR!! the key is that the car goes threw the test while the engine is running ...

if the car is turned off ... u will have to repeat procedure ...

Your best bet , take it to a qualified repair shop .