Hi All,
Hoping someone can give some ideas on my problem.
I have owned my 1998 Indy Pace Car for about 15 months now and love it. However, it has a problem that was mentioned when I was buying it and no one up to now has been able to correctly diagnose and fix it.
The problem occurs when I am going into a corner and the front brakes lock on. Well I think it is the ABS cutting in because the wheels don't actually lock, they just sort of grab, let go, grab let go etc. I don't have to be going into the corner hard and not necessarily braking either. The problem disappears as soon as I straighten up. It feels like it is locking up in the left hand front wheel. If I turn off the Active Handling then the problem disappears.
I don't know very much mechanically so I have to take the car to mechanics and the biggest problem we have here in Australia is that there are no dealerships or factory trained mechanics, therefore not very much knowledge and no proper equipment.
One mechanic replaced a lower steering column sensor thinking that would fix the problem, but no joy there.
Another looked at the ABS unit at the front of the motor and replaced the electronic module part but still no joy.
I have another mechanic looking at it now and they have cleared all the past and current codes from everywhere. The problem is still there but last advice was that it wasn't throwing any codes. His thoughts are that it may not be electrical and may be mechanical.
So, that's about it.
Any ideas?

Thanks in advance.
George.

 

Are you saying the Brakes apply, when you're not touching the brake pedal? Do you know how to pull up the Trouble Codes on the DIC?

 

With engine off, turn key to on position, then press and hold down Options, and while holding Options down press Fuel 4 times. Tell us what codes come up.

Note: Buttons I'm talking about are the ones to the right of the steering wheel.

 

Check wheel bearings also. Can you disable the abs completely and do a test run? Any clearance issues with the tires hitting the inner fender well? Oh I just saw that its okay when disabled. HMMM?. How does the brake fluid look?

 

It sure sounds like your car has an Active Handling issue. If you aren't cornering hard and it is doing this either the steering sensor, yaw sensor or wheel alignment could be the problem. Since the one guy replaced the steering sensor it looks like it could be the yaw sensor or alignment. If AH is acting normally the left front brake would be applied if the car was experiencing oversteer with the left rear swinging wide. That brake application would tend to reduce the yaw rate and point the car in the direction you are turning the steering wheel. There seems to be a range in the various sensors where they aren't performing correctly but they aren't far enough out that they throw a code. If a code was thrown the EBCM would turn off AH and traction control. If the toe settings are off the steering sensor may be turned just enough in one direction that it causes the system to activate. One other thing that should be checked is wiring between the steering sensor, the EBCM and the yaw rate sensor to make sure there is no corrosion in the connectors, that good ground and voltage connections are available. If you have the Service Manual for a 98 just be aware the schematic for the sensors is in error and the 5V and Ground in the yaw sensor module are marked incorrectly. Those two words should be swapped.

Bill

 

please keep us posted, I'm interested in the end results

 

turn off your "AH" and take it for a ride and see if it does it.

If not you could have a bad speed sensor, wheel bearing or other "AH" related part, like steering sensor or lateral sensor next to passnger seat.

 

What wheels and tires do you have?

 

Hi All,
Thanks for the replies and your interest. I am going to get my mechanic to log into this site to check out your questions and suggestions.
However, I can answer some of your questions.
The wheels and tyres are standard and I think the tyres are still the original (the car has about 60,000 klms on it now). I did a wheel and tyre swap with a mate of mine who has a '98 and the problem was still there.
I bought the car when it had about 44,000 klms on it and I haven't changed the brake fluid since I have owned it.
I have had the left hand rear wheel bearing/hub replaced and the mechanic checked all the others and said they were fine.
My mechanic who still has the car said that he has had all the disc rotors machined as there was run out in all of them. Not very much but he wanted them to be spot on.
Will keep you posted once my mechanic has looked at all your suggestions.
Many thanks.
George.

 

Lube the pins on the sliding calipers.

 

Hi All,
An update from my mechanic.
All wheel bearings are good.
Pins in the calipers are perfect.
The car doesn't pull either way and the tyres are not wearing unevenly so we think the wheel alignment is good.
He is basically scratching his head about the problem, and I told him others have looked at it before but he said he wants to be the last so I gave him your suggestions and he will work through them.
Any other ideas will be greatly appreciated.
George.

 

Time for a Tech2 that can record the event and tell ya what's up.

 

I'm sure your vehicle has had at least one brake job, brake pads and rotors or maybe just pads.
Take a look at the brake line itself. Make sure the brake line and caliper wasn't twisted in a loop before it was reattached to the bracket. Check both sides.
Good luck, and keep us posted

 

George,

This is off topic, but how many Corvettes are in the Brisbane area? My daughter moved to Cairns about a year and half ago from the states. Miss her a lot. There maybe a trip there in the near future.

 

Hi All,
Update time.
Brake lines are good.
We got a Tech 2 that reads all the codes and the mechanic has noted them and then erased them.
The problem is that now there are no codes coming up but the brakes are still grabbing. I have got the car back over the Christmas toNew Year break as the mechanical shop only reopens on the 11th Jan. At least I have been able to have the car over the break and get some driving in.
That's about all the info I can give at this stage.
Any thoughts guys?
George.

 

Bill Dearborn has given solid advice & I would persue that route before all else. This is WAG but too bad you couldn't get one of those camera's that you attach to the car & place in the wheel well where the problem exists just to get an eyeball on the issue as it is driven. Maybe it will show something that can't be scanned??? Was the brake fluid completely flushed and did it flow without restriction?? I had a brake lockup on a C3 due to disintergration of the brake fluid reservoir cap gasket which in turned gunked up the fluid and caused a brake lockup problem that had progressed at a rapid pace. Flushed it and replaced master cylinder and that was the fix. I'm doudting that is it in a C5 but strange things can happen.Good luck as I'm sure it will be figured out. Any rocket scientists out there?

 

my best guess would be a wheel speed sensor or a steering sensor. it is not uncommon for a wheel speed sensor to fail.

 

Bill is right on target! The Active Handling System is attempting to correct what it thinks is an error. You stated it doesnt have the issue with the system on OFF. That tells you that the Brakes, and brake components wheels, tires, rims, lug nuts etc........are NOT the issue.

It all boils down to an active handling sensor. Here are the primary ones to examine:

Yaw Rate Accelerometer
Linier Rate Accelerometer
Steering Wheel Position Sensor
Defective wheel speed sensor signal When a wheel speed sensor fails it sets a DTC. You stated that you have NO DTCs so, its most likely not a wheel speed sensor issue.

How are you reading and clearing DTC?

You know that you can read and clear your own without a TECH II?

READING YOUR Engine Diagnostic Codes



The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current C code indicates a malfunction is present and active in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes.
More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except English/Metric (E/M). Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press and hold the RESET button To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:


http://www.corvette-web-central.com/C5DTCcode.html


http://www.obd-codes.com/trouble_cod...d-ii-codes.php



Make sure to include the H or C suffix!!



You can use the TECH II to read the sensor data in real time and see what sensor signal is causing the EBTCM to activate the brakes.

One other thought and I have had this very issue on my 02 ZO6. The EBTCM could also be bad. Thats an expensive egg so,,,,rule out all the other stuff first.

BC

 

Hi,
Thanks for this guys.
I will print this out for my mechanic.
Will keep you all posted on the car's progress.
Regards,
George.

 

Hi again everyone,
Alan, my mechanic is back on the job and he has sent through these ideas. What do you think?

"1. Brake fluid was flushed totally
2. Codes were checked and cleared initially with Tech II. However, when codes were checked manually one or two remained in the system(not problem related) and were cleared manually.
3. Everything does seem to point to yaw sensor etc, but according to the manual if any of these sensors were faulty a code would be produced. Ofcourse that doesn't mean there isn't a problem with one of the sensors, past experience tells me that. If time & money were no object then I would replace all of the relative sensors, but that is not practical and may still not fix the problem.
4. Next plan of action is to remove and test all the sensors individually with reference to the manual.
Just to note, wheels do not lock up, they partially apply the ABS.

Yaw sensor etc became really to the force, when cornering with freshly ground discs. You could hear the ABS unit working but it didnt slow the vehicle at all. Once the discs were bedded in (5 or 6 breaking cycles) the problem returned to its normal state. The problem arises only when braking slightly into a corner at a brisk pace, by corner i mean like a suburban street corner. I.E. late apex with about 110deg, steering angle over about 35 - 40kph, which ofcourse brings the yaw sensor etc to mind. (my addition - this problem will occur even if I am doing a U turn from a standstill.)

All advice to date has been helpful and I would appreciate any input, no matter how obscure it is."

That's it from Alan.
Any suggestions guys?