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My service stabilty system has come on on my 2004 GXP. The car has about 47k miles. What might this be? It seems to come on when I am at full highway speed of 60-70 mph.

First off, Welcome!!


What happens at that speed? Just the light comes on, or does it apply the brakes? The only way to know is to have a dealership or someone with a Tech II scan tool scan it and see what code comes up. Are the ABS or Traction Control lights on? If so, it is probably a bad wheel speed sensor, and will cost about $130 + labor. If not, it could be a couple sensors that deal specifically with the Stabilitrak System. I've been dealing with the Service Stability System light since I've had my 2003, and my 2000 before that had the light as well.

The car does not apply the brakes but it did come on today when I slowed down at a stop light and was stopping there. The traction control light is still on too. I desperately need new tires and plan on getting those soon. My front end and tires need to be balanced too. I have noticed it is usually when I slow down a llttle from the speed I am driving. This is the third day this has happened. It happened about six weeks ago then on Friday. I did not drive the car yesterday. It came on twice today. It came on. We stopped at a store and it reset then several miles down the highway it came on again.

I'd be willing to bet it's a wheel speed sensor. That is located in the wheel hub, and the entire assembly needs to be replaced.

Ok, guys, if you're NOT sure of what the issue is, please don't offer advice! Boards like this are great, but they can be bad too! If the OP went and replaced his wheel hub assembly based on the above suggestion, it would be wasted money when the system activated this fault again. I'm not trying to be mean or anything...

Three sensors drive this, and then include the ECBM (Electronic Brake Control Module). Those sensors are;
1) Steering Wheel Position Sensor
2) Lateral Acceleromator Sensor
3) Yaw Rate Sensor

We all know what the stability control system does. It's pretty obvious. But knowing how it goes about it's business is key to figuring out where the problem lies.

Essentially, the Stabilitrak is activated by the electronic brake control module (EBCM) which calculates a desired yaw rate then compares it to the actual yaw rate input from your driving. The ECBM determines this desired yaw rate from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between this desired yaw rate and actual yaw rate is teh yaw rate error, and is measured by oversteer or understeer. If thta 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.

To test the system, you'll need someone with a Tech2, or other suitable 2 way diagnostic tool.

You'll need to start the car, go into the stability system menu, observe whether or not the system is centered over a certain time frame (probably about a minute). If it comes back as yes, then it's most likely a loose connection in the wiring harness somewhere. If not, you start testing those three sensors.

Steering Wheel Position Sensor: Run a test in the Stability system. Does it pass? Yes, we keep testing on the other two sensors. If it doesn't, replace the SWPS.

Yaw Rate Sensor: With the scan tool in the stability menu, observe the yaw rate sensor input. I think it should be about 2.5V plus or minus a few tenths. If it is, we move on to the Lateral Accelerometer Sensor. If it isn't, replace the Yaw Rate Sensor.

Lateral Accelerometer Sensor: With the scan tool in the stability menu, observe this sensor input. I think it should be about 2.5V plus or minus a few tenths. If it is, this is where it gets ugly as now the ECBM needs to be tested. If it isn't, replace the Lateral Accelerometer Sensor.

If you've gotten the above checked, and we now need to look at the ECBM, confirm whether or not DTC C1248 AND C1255M3 are in your stored DTC's. If so, I think the ECBM needs replacement.

Once again, not trying to be mean, but no where in any of this do I see a wheel hub assembly being mentioned!

LOL basically you have to take it to a reputable shop with a Tech II scanner.

Which is what I said in the first post, but I also said that I thought it needed a WSS/Hub. Have it scanned to be sure. I guess I wasn't clear.

CMNTMXR, It is my understanding that the Stabilitrak gets its vehicle acceleration information from the WSS located in the hub assembly. If the WSS is bad, the Stabilitrak can't get the proper information, and the service stability system is lit. Please correct me if I'm wrong, I love to learn.

The accelerometer will tell it the acceleration, the WSS tells it the speed of the vehicle. I have not done a lot of reserch on this, but from what I have seen, the WSS will affect the ABS system first. That is the most important input into the ABS system so that it sees which wheel is stopped while the others are turning.

Mine comes on periodically then goes back off. No drivability issues. Never concerned enough to do anything about it.

00Beast wrote:Which is what I said in the first post, but I also said that I thought it needed a WSS/Hub. Have it scanned to be sure. I guess I wasn't clear.

CMNTMXR, It is my understanding that the Stabilitrak gets its vehicle acceleration information from the WSS located in the hub assembly. If the WSS is bad, the Stabilitrak can't get the proper information, and the service stability system is lit. Please correct me if I'm wrong, I love to learn.

As mentioned by myfirstbonnie, the VSS in the wheel assembly is used to tell the system what the actual speed is of the vehicle (for many needs, not just the stability system). The lateral accelerometer on the other hand, is used to tell the system at what RATE the vehicle is accelerating.

Both pieces are important pieces of data that Stabilitrak needs. Particularly in determining the vehicle's actual yaw rate vs. the desired yaw rate. This variance is what tells the system whether there is oversteer or understeer.

I gotta side with Ed on this. 99% of the time, Stability issues are wheel speed sensors, or the wiring going to them. And that is speaking from EXPERIENCE.

Still gotta scan it to get an idea of where to start though.

Not to split hairs or anything, I speak from EXPERIENCE too. I only worked on them for a living to put food on my table and clothes on my back. The information I posted above is what I was trained on, BY GM. You know, the people that designed, engineered, put this car together, and then trained me to fix it when one of their brilliant systems went haywire.

There are three pieces used in the stability system that require replacement when the stability system becomes inoperative and you've troubleshot it correctly. I have listed those above. In addition, the electronic brake control module (EBCM) can be a culprit too.

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 transaxle. This is NOT to be confused with your WSS out at the axles.
Lateral Acceleration = Lateral Accelerometer sensor located under the rear seat near the electrical center.
Yaw Rate = Yaw Rate Sensor located under the reat parcel shelf in the trunk.

This IS from EXPERIENCE!

Edited for spelling.

If you unplug the WSS, you get ABS, TRAC OFF, and Service Stability System on the dash.

We have hundreds of SSS topics on this board. I can think of 2 where the EBCM was replaced, several where the SWPS was replaced, but ZERO lateral accelerometer and yaw rate sensors replacements.

99% of the time its wheel speed sensors. Yes, they may not be part of the designed system, but they do play a major part when they go bad.

The wheel speed sensors can, and do set the service stability system warning. It will usually also set the traction control and abs lights. I had it happen when the WSS in the replacement hubs went bad and problems reported on the board says that is the most likely cause, followed by the steering position sensor.

The short answer on this regarding OPs post is that the vehicle needs to be scanned to find out where the problem lies.

This is a question for CMNTMXR57. I have a 2006 Pontiac Grand Prix GXP (LS4) and have a similar issue (Stability, Traction Control, ABS, Brake Light). I was able to get the codes when my friend had his reader connected (C0896, C0898, U1017 and C0550 - there may have been more, but that was all I could get written down.) He also brought up the speed sensors and we drove the car -> all wheels measured the same speed. With this information, can I rule out wiring and speed sensors? I printed out Nov2,09 and Jun28,10's and will try them as well. Anything else I should be looking at? THX

Welcome to the forum!

This is an eight year old thread. It's always a better approach to start a new thread and reference this one if you have similarities with your current problem, just give its age.

Hopefully there will be some advice available here to get your problem solved

I'll have to look up the codes later (I don't have my PC with SI on it with me), despite my best efforts to memorize everything. :p