Was driving my '02 Z06 w/32k miles on the highway at approx. 75 mph, when suddenly the ABS, Traction Control, Active Handling lights came on. Strange thing is, this happened the very instant after a nearby strike of lightning hit the open desert about 100 feet off the roadway. No evidence of cosmetic damage at all to the vehicle. Don't know for sure if this caused the problem, but it seemed awful coincidental? Anyways, I pulled over and proceeded to read the DTC. Only one code was thrown (TCS c1233). I checked all the fuses related to ABS, Trac Control, and even a few others...all were fine. Went to start it and no warning lights on in the dash anymore, and everything seemed fine until I hit 10 mph, then all the same ABS, Trac Cntrl, Active Hndlng lights come on. Went home to do some research and self-diagnosis....found the tcs c1233 code to be a "RF wheel speed circuit open or shorted". Checked all connections from wheel speed sensor to main harness, swapped left and right harnesses, and same thing happens, same code is thrown. Did further testing and found ABS and Trac Cntrl both functional under 10 mph, but then disabled when reach 10 mph. This is not intermittent and happens at every key cycle. Then at idle, disconnected harness and found the same exact dtc code thrown again. So my conclusion is for some odd reason at 10 mph, the RF wheel speed circuit "magically" opens or shorts, then resets itself when the key is turned off. I tested the resistance of the wheel speed sensor (with wheel not spinning) and found it to be normal at 1130 ohms resistance, however I did not test the WSS with the wheel spinning, which I was going to do today. Should the resistance value be any different at different wheel speeds? Seems I can rule out wiring harness and grounding issues, and am leaning towards the wheel sensor being bad, but can I rule out the EBCM? Anyone have any ideas on what is causing this??? Thanks

 

Don't rule out your grounds until you check them. I had identical symptoms and ended up finding the front most ground on left frame rail loose. Cleaned and tightened --- no more nutty codes. The remainder of my grounds in engine compartment were OK.

 

I'll look them over - again....now I am really at wits end because after hooking up a new wheel hub assembly (bearings, hub, and sensor in one) and spinning it DID NOT solve the problem. Maybe I will just remove and clean every ground no matter what it looks like and hope for a miracle. ?????

 

I have had this issue but mine freaked out at 42 mph! Someone else had one that crapped out at 105 mph.

Most liklely a BAD EBTCM. There very complex and get flukey at times. Your best bet is to swap the short jumper harness's from side to side to rule them out as a source of the problem.

Here is a link to the most recient EBTCM issue!

http://forums.corvetteforum.com/show....php?t=1745355

Get your EBTCM rebuilt by ABS fixer!

Hope this helps.

 

Thanks for the tip and thread link...it gives me a bit more confidence in making that leap of faith. I did swap the jumper harnesses from right to left with the identical 1233 thrown. So by deductive reasoning this SEEMS to be the likely option! I am thinking I will go that route - I will update results after I go ahead and R & R the EBTCM. Thanks

 

Here's my tutorial on the EBCM. If you want the photos, PM me your email address:
Let's cover some basic information on AH, TC, and ABS. In simple terms, these three systems combine data from wheel speed sensors, yaw rate sensors, steering wheel position sensors, along with brake and throttle inputs to determine what the driver wants to do and detects any lose of traction and take corrective action by pulling back on the throttle, activating brakes on individual wheels, or releasing brake pressure as needed to maintain traction.

What goes wrong

When there is a problem anywhere in the system, the computer does not know what's going on with the car or cannot respond correctly. Rather than risking the wrong response which could potentially wreck you car, the whole system is simply disabled for the remainder of the ignition cycle. At this time you will see the ABS and Traction Control warning indicators illuminated on the instrument cluster along with the following messages on the Driver Information Center (DIC):
- Service ABS
- Service Traction System
- Service Active Handling

At this point, you can safely continue to drive your car, just remember that your electronic driving aids are no longer functioning so you should adjust your driving habits accordingly.

Troubleshooting

As I said before, when there is a problem the system is deactivated for the remainder of the ignition cycle, so sometimes everything will go back to normal if you just turn off the car and restart it. If that corrects the problem, it was either a glitch in the system, a lose connection that's going to come back soon or an early sign of a future failure that is coming. Even though the system is now functional it is still beneficial to continue to trouble shoot. The history code should give you a good idea of what to check

The next step is to see where the fault is. If you have several different codes write them down, clear them, and see which ones come back the next time you start the car. At this point, I'm betting that the codes point to either the EBCM or the wheel speed sensors. We'll get to the wheel speed sensors later, for now, let's get to the EBCM.

Electronic Brake Control Module

The most common code for the EBCM is C1214 - Sol Valve relay Contact or coil CKT Open. This code is set when the system voltage is less than 8 volts for 0.23 seconds. Since our goal is to fix this for the lowest price possible, we'll start checking things we can fix for free

The EBCM sits between the engine and radiator. You can see it in the picture on the left below. The EBCM is on the left with the large wire harness coming into it and the sticker on top. The Brake Pressure Modulator Valve (BPMV) in on the right with the brake lines coming out. The EBCM is a dry module, meaning that you can change it out without having to worry about bleeding the ABS system. All of the brake fluid is contained within the BPMV. The coils (seen in the picture on the right below) fit over small spools that have valves inside them. The valves are operated by an electromagnetic field supplied by the coils.




Start by doing a quick visual inspection of the wires. If there are any obvious signs of damage, you've likely found the problem. One member had a problem with the wires rubbing the serpentine belt



Also check to make sure the wire harness has a good connection. If the connection appears solid disconnect it (see step 3 in the replacement instructions below) check the pins to ensure that they have not been bent or damaged in any way. If there is any sign of corrosion, clean it off. Once everything looks good, reseat the harness.


Next, let's move on to the grounds. The EBCM is grounded to the chassis on the left frame rail, just forward of the engine. It's the Black box right in the middle of the picture. As you can see, it's real easy for dirt and moisture to get in that area which isn't exactly good for electronic components. Even if you never drive your car in the rain, it'll still get wet when you wash it, and that could be enough



Start by unbolting the chassis ground, then take the chassis ground connector apart.


These pictures show the corrosion that can build up in the ground connector. If you chassis grounds look like this one, you've probably found the problem. Even if they don't, go ahead and clean it up with a wire brush before putting it back together. Also clean off the chassis and bolt to make sure you've got a good clean ground.

*If you are having any other electrical issues, it's a good idea to check the grounds. These pictures show where the other grounds are.
At this point, we know all of the wires are good, but for some reason enough voltage is not getting to the system. It is possible that your battery is not functioning properly. If your battery is a couple of years old, has been drained and recharged a couple of times it might be a good idea to go ahead and replace your battery. This is a long shot for EBCM issues, but I think it's worth a shot before spending several hundred dollars for a new EBCM and you're going to have to replace it eventually anyways. Old batteries can cause a variety of minor electrical issues and you likely have a bunch of history codes for minor issues if the battery is causing the problem.


Now on the EBCM itself. If the electrical contacts inside the relay are dirty or burnt, the vibration from striking the module may change the symptoms or may clear them up for a while. This is by no means a fix or a cure all, in fact it could make it worse or it may not do anything, it's just something to try. Use a small plastic hammer or something similar, lightly tap the front of the EBCM on the lower right corner of the module. The area will be on the right hand side of the lower electrical connection seen in the picture below.




At this point, You've got to additional possibilities. Replace the EBCM or replace both the EBCM and the BPMV. The service manual calls for you to measure the resistance between each pump motor control circuit and the housing of the BPMV, if that checks our okay, you replace the EBCM if not you replace them both. Since most people do not have the equipment to do this the best we can do is to replace the EBCM. If that doesn't work, you'll have to go back and replace the BPMV.

The procedure for replacing the EBCM is very simple. The only special tool you need is a T-20 torx screw driver. I have a Craftsman tool set that has a 1/4" drive screwdriver with and adapter for many different size bit. Unfortunately, the adapter was to long to fit between the EBCM and water pump, so I purchased a set of Craftsman 5 pc. torx screwdriver set that worked fine. A flathead screwdriver may also be needed to pry apart the EBCM from the BPMV

1 - make sure the car is off.
2 - you will probably need to remove the airbridge to get to the EBCM.
3 - remove the wire harness by first removing the white plastic clip that locks it in place (I cut it off and replaced it with a zip-tie) (picture 1), then lift gray handle and pull back on the wire harness (picture 3). At this point, you will be able to see the second wire connection that is removed by pulling down (picture 3).
4 - The service manual call for you the remove the 2 insulator nuts that hold the BPMV to the brackets and lift the EBCM/BPMV out of the bracket. I do not think this step is necessary because there is plenty of room while it is still in the bracket and you do not gain much additional clearance since the brake lines restrict the movement.
5 - Remove the 6 T-20 torx screws connecting the EBCM and BPMV - 1 on each corner and 2 on the sides (picture 2).
6 - "Separate the EBCM from the BPMV by gently pulling apart until separated" - I should start laughing here, but it's not that funny. It's been my experience that anytime the instructions call for you to do something gently, nothing gentle is going to work. In this case, I had to use a flathead screw driver to brake the seal. Once it moved a little, the rest was easy. In addition to the rubber seal, each of the 12 holes you see in picture 3 have a peg in them from the BPMV. Don't go crazy, but be prepared to force them apart.
7 - At this point, all you've got to do is put it all back together. push the repaired (or new) EBCM onto the BPMV.


An alternative to buying a new one is to have your original rebuilt.
For EBCM repair/replace

Call Brandon 877-648-7530 at ABS FIXER

or: www.absfixer.com

$150. plus UPS....warranted as long as You own it

8 - Replace the 6 T-20 torx screws
9 - reconnect the wire harness
10 - put the intake back on

picture 1 picture 2 picture 3


At this point, the AH/TC/ABS should work normally. If not, you've also got a problem with the BPMV. Although you could replace the BPMV yourself, you have to bleed the ABS system which requires Tech II. For those of you like me that don't have access to Tech II, you've got 2 options. Replace the BPMV yourself and tow the car to a shop with Tech II to have it bled, or just take it in to have the BPMV replaced. The advantage is that you've already done all of the trouble shooting so you want have to pay the mechanic to diagnose the problem for you.

 

*UPDATE* I went ahead and bought a refurbished ebtcm at absfixer, installed, and problem solved!