I asked about this a little while back but it was only happening when it was raining. I get service "active handling, traction control, and ABS" and like I said before it was only happening when it was raining now they trip as soon as I start the car. I have bigger wheels and tires out back than what were on stock. When the car was re-tuned I am pretty sure he tuned in the new tire size. Also this past Friday I was in traffic and active handling kicked in and threw the car across my lane. Lucky no one was in the other lane or I may had hit them. Does anyone know what the issue is? Thanks for the help

 

Bigger wheels on the back of the car will trigger the warnings you mention. I've never heard of "tuning" for bigger rear tires except for speedometer accuracy.

Your only solution is to get "bigger" front tires to complement the larger rears.

 

im running 19x10 (285/25/19) up front and 20x12 (345/30/20) out back. I understood it would do this while driving but why would they trip when the car is stationary??

 

They aren't "tripping" while stationary. The codes are set and will remain until you erase them with a code reader or correct whatever is causing the code.

You have a major mismatch in F to R sizes.

The Fronts are down 1.11" in diameter, down 4.3%
The Rears are UP 1.3" in diameter, up 4.8%

Get larger diameter fronts. Try http://www.tacomaworld.com/forum/tirecalc.php for sizes.

 

And I'd do it as soon as possible! You are lucky, so far, you haven't had a serious accident yourself or with someone else.

 

That makes since but what I dont understand is why some times when I get in the car and start driving all 3 will flash at me other times only 1 will flash and its different ones some times when only 1 flashes at me.

as for the larger fronts I dont think I can go any larger or I will rub. Im running the stock tire size of the ZR1 up front

 

Why?

 

When I had that problem on my first C6, it was a bad ground.

 

You're not running stock size up front if you are running the 285/20/19 that you claim. Stock Front is 285/30/19.

Stock rear is 335/25/20?

 

Your tire selection will only cause an Engine Drag Control message as the rear tire is turning to slow in relationship to the fronts. The standard ration from front to rear is 1.04 and your ratio is 1.08 so the rear tire is too large.

However, those sizes won't cause Service Message messages for ABS or Active Handling. If you get Service ABS, Service Traction Control and Service Active Handling messages at the same time you have a failure that is common to all 3 systems. Wheel bearings are common to all 3 and you can have connection issues that are worse in damp weather. Ground and power are common to all 3 and they can be subject to failing under damp conditions.

The steering sensor is used to initiate Active Handling. You turn the steering wheel and the EBCM uses the steering sensor input along with the lateral G and yaw sensors to determine whether the car is responding properly to your steering input. This is where different tire diameters can bite you in the butt since the EBCM is calibrated for tires that are a specific diameter with a certain type of friction characteristics. Since the EBCM is expecting the car to respond in a certain manner to its corrective actions your changes could make it slower or faster to respond than expected this puts the EBCM into a situation where it is trying to catch up with the its own corrections. I doubt your tire sizes will cause this type of an issue.

Check your wheel bearings/hubs for looseness, check the ABS connections where the WSS sensor plugs into the car's harness and check the EBCM grounds and power inputs. Trace power and ground connection all the way back to the battery to make sure there are no loose connections, corroded connector pins, etc.

It probably is a good idea to see if you have some sort of history code for your unexpected AH activation. You will need a scanner that can read ABS codes to do that.

As for your tuner there isn't a thing he can do to affect what the EBCM does. It is a closed system and tuners don't have access to the code in the EBCM. The EBCM doesn't use the vehicle speed data going to the ECM it uses the wheel speed sensors from all 4 wheels.

If you see a service message don't turn off the car until you have read the ABS codes. If you turn off the car some ABS codes get reset and they could disappear with the next engine start.

Bill

 

After reading this I went out and doubled check I am running 285/30/19. I don't think they make 285/25/19

 

I know where some of this is but I dont know where the EBCM harness is or the WSS sensors. And when I check my wheels bearing/hubs what am I looking for. And thank you for the knowledge dump, you have a usb port I can download this info lol.

 

EBCM is located under the alternator. It is attached to the brake pressure modulator valve which is the thing with all of the brake lines going into it.


Wheel speed sensors are part of the wheel bearing and they have a two wire harness terminated with connector that comes out behind the knuckle. The car harness plugs into each one. When you take off your wheels you should be able to look behind the rotor and see the connectors attached to a thin bracket.


Bill

 

I agree with Bill that there may be multiple failures here, but the tire size issue is not going to go away until you return to the proper front to rear size ratio. I would suggest doing that first and then investigate any further codes and lights that are generated. The car thinks that the rear tires are slipping on the pavement because they are going too slowly compared to the front wheels. By changing tire sizes, you have essentially speeded up the fronts at the same time as you slowed down the rears. This problem can only be corrected by changing the tire sizes.

 

If would be nice, for a (or my) total understanding, to have a functional overview - in the form of a diagram preferably - that shows how all the various control modules (ECU, EBCM, TCM, etc.) interact. In particular I mean which data are input to a certain module, which data are output from a module, and what the expected "normal" value ranges are that are expected by those modules.
I have tried to find said functional overviews via Google, but in vain.
Bill, thanks nevertheless for your clarification.

 

Attached is a description of the system from the FSM.


Bill

 

Wow, this is very useful information! And sharing information like this with fellow members is exactly one of the reasons why Corvette Forum is such a great forum!!

I receive exactly the same messages as Mike (the OP), but (like him?) intermittent and seemingly quite random. The only way that the mechanics at my dealership have "resolved" the aforementioned messages is via trial and error, without any success. It has cost me a small fortune already because of all the labor that was involved. My EBCM was replaced also (that alone being $700), which did not help either.
Now I have a document that I can show to them, and hopefully enables them to obtain a better understanding of the complete picture.
Bill, thank you very very much! I really appreciate that you shared this description. Did you assemble it yourself?

Ronald

 

I have not been able to check anything due to the beautiful weather we keep getting. As for changing the tire size that most likely wont happen. The reason I did the wide body upgrade and the bigger wheels is so i could run 345s out back. I know Nitto has them in 25s but I love my Michelins. I need to change out my alternator so I will be checking everything out when the weather gets better. Thanks again for everyone's help I will update with any solutions.

 

You can keep the 345's in the back IF you change the fronts to a taller tire. At least three of us on this thread have told you you need a taller front tire, ignoring our advice doesn't gain you anything.

 

I know I am not the only one running 285/30/19 up front and 345/30/20 out back. And a lot of them are not having this issue. My issue of going bigger up front is that I will rub to much because I rub as it is.