Posted numerous times before. This is a general explanation and troubleshooting where both the stability system
AND ABS errors are generated. It is not STS-V specific but it is from GM, although I can get the specific STS-V list.
There are three pieces used in the stability system that require replacement when the stability system becomes inoperative and you've troubleshot it correctly. Where the two systems cross (ABS and Stability Control) is in step #1 and step #6, those being WSS and the electronic brake control module (EBCM).
1) First you perform an ABS system check. If there is a fault in the ABS system, this is where the WSS comes into play. But NOT anything to do with the VSES!
2) you check that the VSES (Vehicle Stability Enhancement System) centers for roughly 30 seconds. If it doesn't, go to step 3, otherwise check all connections and wiring harnesses for intermittent connections.
3) Using your T2 (or equivalent), perform a steering wheel position sensor test. If the SWPS checks out, move on to the next step. If it doesn't, replace the SWPS.
4) Using your T2 (or equivalent), check the lateral accelerometer input voltage in the VSES. It should return about 2.5v. If it does, then the next step will be to test the yaw rate sensor. Otherwise, if it doesn't, replace the lateral accelerometer.
5) Using your T2 (or equivalent), check the yaw rate sensor. It too should return 2.5v. If it does, move on to the EBCM. If your yaw rate sensor doesn't return 2.5v, replace the yaw rate sensor.
6) Replace the EBCM. If it isn't programmed/setup properly, that could be the problem, and you'll be generating a C1248 or C1255M3 code and possible incorrect operation of the system.
No where in ANY of this, other than making sure the ABS system is funtioning correctly, is mention of the wheel speed sensor (WSS), wheel hub, etc. Why you ask?? The WSS is ONLY used for computational needs of the ABS/traction control system. NOT the Vehicle Stability Enhancement System (VSES).
I just went and looked in my Techline manual for 2004. This is EXACTLY, verbatim, from GENERAL MOTORS;
The vehicle stability enhancement system (VSES) includes an additional level of vehicle control to the EBCM. The VSES is activated by the EBCM calculating the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.
The VSES activations generally occur during aggressive driving, in the turns or bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the brake pedal will feel different than the ABS pedal pulsation. The brake pedal pulsates at a higher frequency during VSES activation.
Steering Wheel Position = Steering Wheel Position Sensor (SWPS) located in your steering column
Vehicle Speed = Vehicle Speed Sensor (VSS) located on your transmission. This is NOT to be confused with your WSS out at the axles.
Lateral Acceleration = Lateral Accelerometer sensor
Yaw Rate = Yaw Rate Sensor