I apologize if this is a frequently addressed issue...

2001 model with aftermarket Z06 style wheels (18/19 inch). I'm also getting the traction control/ABS etc errors about 90% of the time each time I drive.

Before I get started troubleshooting grounds, EBCM, etc, will the fact that I have 18/19 inch wheels and not 17/18 inch stock wheels make a difference in triggering the errors? I'd hate to go through all the work only to realize that the wheels will always be an issue.

Thanks in advance!

 

My first thought would be what are the rolliing diameters of the tires front to rear? The stock setup uses smaller diameter tires in the front than in the rear, and I would think the traction control algorithm takes this into account. If the diameter bias is outside that algorithm, it thinks something is wrong. My $.02 but more technologically astute need to chime in.

 

^This.
What size tires are you running front and rear?
Ideally you would want the front diameter to be 1" smaller than the rear. Some people have gone as little a .5" and as much as 1.5" difference, but it gets real "iffy" at those margins.

 

You need to tell the PCM you changed the tire size front and rear with editing software. The PCM is looking for 17/18 size tires if it still has the stock parameters.

 

you should also post your codes to make sure your on the right trail.

 

It's the C1214 code.

Sounds like I should pursue the troubleshooting. I'll look into getting the TPMs next time I get tire work done. If I get into a bind, I have a friend with a TPM programmer and I can get him to help me out.

Thanks for saving me the time!

 

That is an ABS code. I have always had the theory in troubleshooting-"what changed"? In your case wheels and tires. While my in depth knowledge is with BMWs (21 years), having recently returned to the Corvette fold, most things "operate" the same. For ABS/traction/slip control, the computers use a counting ring on the hub, and compare the rotation (velocity/RPM) of all four corners, or front/rear (ABS), to determine an outcome. E.G. for ABS, if one wheel is rotating more slowly than the other three, it is determined that the wheel is "locked up" and braking (hydraulic pressure) is reduced. With traction control/slip control the idea is the same--something's going faster or slower than it should, and brakes are applied or released. When the programmed algorithms are exceeded, the system says "tilt" (code)-something is wrong. If your tire diameters are not "staggered" sufficiently, the computer says "tilt" and throws a code. You haven't stated what your rolling diameters are (above +/- limits), but there are formulas to compute them, or you can look them up on the manufacturer's website for your brand. I would bet you the adult beverage of your choice that the tire diameter "split" is your problem. TPMS have nothing to do with it. OUT.

 

That being said, if the wheel tire combo has been on for a while and this is a NEW fault, then it could be the ABS computer.

 

Sorry but that's 100% incorrect. No offense intended.
This is VERY often misunderstood.

Very true.

Its all about the "Diameter" of the "TIRES" you choose. If you up-size the tires correctly then you will have NO issues.

Check out the the information I wrote on my web site about this.

www.ToqueZ06.com
Scroll down to "How to Determine the correct "Tire Size" for new wheels on a C5 and C5 Z06:"

Here is what I did with my Z06 when I upsized from 17/18 wheels to 19/19 wheels.

Front
Stock 17" Z06 Wheel = 265/40/17 = Diameter 25.4"
New 19" Wheel = 275/30/19 = Diameter 25.6"

Rear
Stock 18" Z06 Wheel = 295/35/18 = Diameter 26.1"
New 19" Wheel = 305/30/19 = Diameter 26.3"

So with my proposed new tire setup:
Front --> Increased the Diameter by only 0.2"
Rear --> Increased the Diameter by only 0.2"

I have never had an issue with Active Handling, or Traction Control.

Its ALL about the Diameters of the TIRES, and has nothing to do with the Rim size.


Please let me know what Tire Sizes your running.
I can quickly let you know if your issue is due to the tire size your running, or another issue possibly.

Toque

 

Just to clarify, I've had this car for a week and two days. The code has been tripping since I bought it, so I don't know how long the issue has been around. That was actually the reason for starting the post to begin with since I didn't know if the codes started when the wheels were changed.

I appreciate the links to the diagnostic instructions for the EBCM. When time allows after family leaves town, I'll get on it. I have a modest electronic background (building/repairing guitar amplifiers), so I don't have any trepidations about tearing into the module and giving the repair work a try.

A question for the physicists based on the discussion about tire diameters... If the diameter specs between the different tire sizes are so minimal (0.2" as stated above), I would question why the error codes don't trip as the tire wears down from new to bald. There's got to be a change in size near that just with wear.

The tires that came on the car are Firestone Wide Oval RFTs. They appear to have been all added at the same time since they have similar wear.

 

In theory, they would wear evenly or proportionally, and stay within the parameters of the "bias" built into the ABS/Traction Control algorithm. Question remains, and several of us have asked you, WHAT tire sizes are currently on the car? See Toques site to calculate your rolling diameters and go from there. I'd do that before I started tearing into a bunch of electronic stuff. FWIW.

P.S. I'm not a physicist, just a hobbyist/grease monkey for 48+ years who's broken a lot of s$%t along the learning curve.

 

Fact is rear tires on the C5 wear faster than the fronts though no one has yet figured out why.......

You're right!!!! Wonder if it has something to do with the right hand pedal???

 

You never read my full explanation on my web site did you.... Please re-read post #12 and go to my web site and read it all.

Its not 0.2". You completely misread what I was trying to explain to you.

Truth !





Your rear tire must be 0.5" larger in diameter than your front tire. If your rear tire is not larger then you will have issues with your traction control, and active handling.

Good luck with your issue.
Toque

 

Sorry, had to wait for everyone to get up before I could check the tire specs.

Front: 245/40R18 (25.7")
Rear: 285/35R19 (26.9")

Toque, sorry I missed your link when I read your post earlier. That's a great tire reference! Looks like my specs should be fine.

 

Lead a horse to water, but you can't make him drink!

 

 

Thanks for checking it out !

Yes you should be fine with your rim/tire sizes.
Your issue should NOT be in your wheel/tire combo.

It must be something else. I would look into some of the other suggestions above.

Good luck with your issue !
Toque

 

Time to start searching for the electrical gremlins per above.

 

Same issues for me. Would my tires cause this?

275/30/19 rear
235/35/18 front

Not trying to hi jack. A lot of good info here.

 

Not sure who chose your tire sizes but They are interesting to say the least. . Your rear is 1.2" larger than your front so you should be fine with Active handling/TC. Your speedo is going to be off though.

Front 235/35/18 - 24.4"
Rear 275/30/19 - 25.6"
Rear is 1.2" larger


Stock C5 diameters:
Front 25.7"
Rear 26.7"

Stock Z06 diameters
Front 25.4"
Rear 26.1"