I just had similar problems with my 2011 Sierra HD pickup (50000 km). Repeated "service active handling" messages with the left or right front brake applying itself. I had to repeatedly shut the system off until I could get it back to the dealer, (I was away from home at the time). When I called the dealer it sounded like it was a fairly common problem, they got me in right away and changed the steering wheel position sensor. Problem fixed so far. Hope I don't have any issues with my 07 C6...
I would join in the letter writing campaign, but wouldn't help from Canada, does anyone know of a Canadian agency that we can write to?

 

My name is David/live in Dallas have a 08 Z51 with telescoping wheel and 20s in rear. Just went to pick up car after breaking in new motor/clutch after tuning and 1 mile away from shop...........felt like ebrake was on.

Turns out.........shop had same issue earlier in the day BUT NO CODES that they could tel and NO warning lights.

Never had issues prior to this last dyno tuning but clearly BOTH fronts were locking.......both were way hot when put in the air.

Without any of the "standard" warning lights coming on does anyone have any idea where to start?

Brand new 800rwhp car and I have this crap happen less than 1 mile away from the shop. Took place on me after making a slow u turn as with many others here........slow /sharp turns but again.......no lights/codes best we can tell??

Thanks when able..........where do I start SWPC?

Thank you

David Snell
dsnell@grandecom.net

 

Dave

Sounds like the shop disconnected the steering shaft from the rack and failed to get it properly aligned when they reassembled it. That will cause the SWPS to become electrically misaligned.
That causes the the car to think its should be turning when its actually going straight. Its trying to lock down the brakes on different wheels to get the car to go in the correct direction.

If it were me, I would investigate that. Any shop with a TECH 2 can examine the SWPS electronically and see if it reads ZERO when the steering wheel is straight ahead.. Right now I bet you have a steering angle input when the car is going straight. Thats a bad thing and would cause the issues your seeing.

NO CODES but you might see active handling engaged on the DIC!

 

THANKS first off these forums are so full of great info!

OK so......I drove the car for over a week with the new motor........NO issues.....and also I had it re aligned as they had the rear of the car out to install the new fuel system when I had the motor put in. I brought it back (week after all that was done) for dialing in the blower/pulley/dyno tuning...and.....they did put a "direct drive" on the front of the motor. NOT sure what that could have effected but maybe something? I also had them raise the rear end 1/2 a inch but front was left alone......not sure this could effect anything??

I left the shop drove out of their parking lot...........drove 1/4 mile and then went slowly over some fairly smooth rail road tracks.............made a slow left hand 180 degree u-turn to turn from a south direction to north.


Soon after less than 1/2 a mile later when slowing for a traffic light.........when I let up on the clutch to roll forward...........felt like the ebrake was stuck. I could move BUT car was noticeably having issues rolling forward freely.


Issue got worse as I limped back to the shop....(brakes heating up I am sure)...........then they disclosed that same issue had happened to them earlier while driving (after) car had been on the dyno for a lengthy tune)

HE said they checked for codes and did not find any by whatever it is they have to check codes.........(may be additional stored?) have to use different source to check they agreed to calling GM guy they use to do this.

they disconnected battery said they touched terminals to clear anything..........drove it for an hour after and NO issues again so they thought it was fluke deal......didn't tell me about it thinking it was corrected

NO lights.........no codes they could tell when it happened to them and to me.

WE put car on the lift and BOTH front wheels could not spin and rotors were OH on fire.........

15 minutes later after.........rotors/brakes cooled down..........BOTH front wheels would freely spin again. Obviously previously heat soaked both were expanded with excessive heat

NO issues on rears while in the air.


SO in regards to the steering column...........it may have been compromised when the motor was out BUT I had NO issues for slightly over a week of breaking in the new motor.

BOTH fronts were "locking" NOT one vs the other...........and issue took place ONLY after they had the car last.

Wondering........if anything they took off the front of the motor to do the direct drive could relate to any portion of the issue?

IF steering column was an issue I would think I would have seen the issue while driving it during the week I broke in the new motor.


Does this bring any additional ideas to you OR would you still suggest checking what you suggested??

I read the BIG long thread about the steering wheel position sensor and active handling failures............

Best I can tell BOTH of my front brakes are engaging when the issue takes place.............and NO visible active handling lights or codes so far!

SEEMS as though it has to be related to something they accidentally did/loosened as it did not take place prior to them dyno tuning the car and doing the direct drive/raising rear of the car? NOT placing blame..........shop is one of the best BUT they too so far are stumped. Just never had issue prior to the tuning, certainly could be a fluke deal with a failing sensor or something that came lose while dyno tuning.

THANKS when able sorry for Nancy Drew short story BUT hope it helps in bringing additional suggestions of what the heck they need to check!

Thank you when able..........

 

For the FRONT BRAKES to engage by them selves, the EBTCM has to energize the BPMV MOTOR and the EBTCM has to turn on the poppet valves to the front brake hydraulic circuits.

SO,,,,,,,,,,,, Either a sensor or sensors are telling the EBTCM that the car is NOT doing what the driver is telling it to and it trying to correct the problem by braking

OR

The EBTCM is defective and has lost its mind and doing random crap.


When things go haywire after a mod or repair, you should always examine the things that were disturbed during that repair/mod period.

If the shop has a TECH 2, it is pretty easy to data log the EBTCM and the AH System and see what its doing. You should see what the SWPS is sending for a steering angle. It should be ZERO when the wheels are straight ahead. There should not be any YAW signals coming from the YAW Sensor which would tell the EBTCM that the car is moving side ways off it center axis.

Without data logging with the TECH 2, you are going to be doing a lot of guessing.

BC

 

They have a GM person who can use this more detailed source of data gathering!

HOPE to know more this next week. All guessing at this point but weird the swps would just fail during tuning etc.

Thank you

David

 

GM should probably be paying Bill for his great advice, expertize and data gathering!

 

From running on the dyno you could'a amazed a bunch of codes that won't show up unless you have a Tech II or a Snap-on scanner.

 

Wow. I just finished going thru about 17 pages of this thread. Very informative and I would like to thank everyone here who have contributed some priceless information.

With that said, I just experienced the AHS issue myself yesterday while trying to make a sharp right turn to get into the right lane. My front brakes completely locked up and my Vette felt like someone was holding it back like a dog on a leash lol. I am grateful that I was not rear ended.

I love this car but I'm not going to let it kill me. So I'm going to see if the stealership would do the fix at no cost. If not, I'll do it myself. Looks like it is easier to complete than installing a new head unit.

Thanks,

Dino

 

I had this service active handling - reduced engine power that almost got me in a bad accident on a bridge.........and there was NOTHING wrong with the car......P2135 that would pop up radomly every now and then.
Replaced the throttle body, and restarting the car would make the code clear....i know it was a bad ground or harness break....I don't like the reduced engine power mode...it is unnecessary, if your car is broken it will stop running, why not just throw the CEL and let the driver know.

I kept getting into these tight spots that were near misses so i just had to get rid of the car. (2004 C5 Z06) I think the "Reduced Engine power" is unsafe.

 

My o5 vette siezed up on me twice last summer. The car came to a sudden stop and the AH light came on. Thank god I was on local street traveling at low speed. I had to shut off the engine for a few seconds and restart it. Man, what a terrible defect.

 

My brother crashed his 06 last year and when I ask him what happened as my brother can drive a car very good. he said I dont know it was weird all the sudden it pulled me to the right and I couldnt get to stop pulling at that point it pulled him right into a pole. I sold a 05 to a guy and the same thing happened to him in traffic the brakes locked up and into a cement barrier he went this is sick that this is happening specially on a car this fast someone could get killed.

 

Did they find the problem?????

 

I called Mr. McHenry and also filed a complaint form. My car won't move because the brakes are completely locked up and the dreaded error message is on the display.

 

And this is exactly why GM will never admit any fault in this.

It will take an act of congress or some serious investigative reporting by an outspoken news reporter to get any results.

Personally, I am thinking about looking into hydraulic corrective measures. Leaving all the GM electrical crap alone... I'd like to isolate the braking system completely from the nanny system. That means plumbing new brake lines and no ABS.

 

I had one with a tuning issue.The temp paramiters weren't changed and the car was stuck in a test mode causing brake lockup.Once we changed the temps it was fine.

 

Mr. MiChener called me back and said the active handling system couldn't' be causing my problem. All I know is the brakes are locked and the car won't move until it sits for an extended period, if you push on the pedal you can't move at all! This is a bit scary since I bought the car used in March.

 

Below is the C6 Brake system flow path for hydraulic brake system. What wheels are locked? Use the schematic and see what would cause the locked wheels to remain locked.

If you disconnect the battery, do you still have a locked condition?




(1) Master Cylinder
(2) Master Cylinder Reservoir
(3) Pump
(4) Left Front TCS Valve
(5) Brake Pressure Modulator Valve (BPMV)
(6) Damper
(7) Right Rear Inlet Valve
(8) Accumulator
(9) Right Rear Brake
(10) Right Rear Outlet Valve
(11) Left Front Outlet Valve
(12) Left Front Brake
(13) Left Front Inlet Valve
(14) Left Rear Inlet Valve
(15) Left Rear Brake
(16) Left Rear Outlet Valve
(17) Right Front Brake
(18) Right Front Outlet Valve
(19) Accumulator
(20) Right Front Inlet Valve
(21) Damper
(22) Right Front TCS Valve

This vehicle is equipped with the DBC7.2 antilock braking system.

The vehicle is equipped with the following braking systems:

Antilock Brake System (ABS)
Engine Drag Control (EDC)
Dynamic Rear Proportioning (DRP)
Traction Control System (TCS)
Vehicle Stability Enhancement System (VSES) (w/JL4)

 

Battery disconnect does not change the situation. All four will lock, only once just the front.

 

If you vent the fittings on the MASTER CYLINDER, do the wheels unlock?

I'm trying to BLOCK ISOLATE. By venting the master cylinder, you eliminate that from the equation. If you vent that and the wheels stay locked,, you have an issue inside the BPMV.

Bill