My active handling system on my 04 coupe has been a problem for sometime. First it was the tranny speed sensor-replaced. Then both front wheel sensors ($1000 ouch!). Now My cruise control is kicking out intermittantly again.

But yesterday I'm going down the freeway and the car starts to shudder for a moment, a bit of shimmy, and the DIC says "ACTIVE HANDLING". Scared me a bit. No error codes on DIC.

I turned the crap AH system off for now. Guess I should go back to the mechanic? Or turn the AH off every time I get in the car?

 

You're asking if you should take it back to the mechanic that charged you $1,000 to replace your two front wheel speed sensors (which didn't need replacing ... I can virtually guarantee that two don't fail at the same time) .....

Oh, and your tranny speed sensor has NOTHING to do with Active Handling ........

NO Don't take it to that "mechanic" ....

How about we start by trying to "fix" it without the help of the mechanic.

Do you know how to display the DTC data on the DIC ?????

https://www.corvetteforum.com/techti...D=26&TopicID=1

Post any/all codes listed except those that start with a U followed by 4 digits ... such as U1064

It is possible you have no code .... yet ... as the EBCM thinks it "reacted" normally to sensor input. You'll know you have a code when you see the SERVICE ACTIVE HANDLING message appear.

Has the car been showing ACTIVE HANDLING WARMIING UP recently ???

Let us know what, if any, DTC are posted ......

 

No DIC codes, that was the first thing I checked.

I do get the occasional ACTIVE HANDLING WARMING UP when first started, goes away rapidly.

Both front sensors were replaced together, as they are integrated with the wheel bearings. I can't find too much fault in replacing the wheel bearings in pairs.

 

I have been working on C5 since 97 and only really seen a hand full of "TRULY" bad wheel bearings. A couple were due to accidents and the rest were due to high mileage High HP abuse. I have NEVER seen an actual wheel speed sensor that ACTUALLY went bad. Ive seen the connector go bad (accident damage) and Ive seen the wire at the entry point of the sensor break, (wasn't installed correctly) but never an actual sensor that went bad. There pretty much bullet proof.

As for wheel bearings being replaced in pairs, if one is bad and the other is good, replacing just the bad one wont hurt anything and is normal. If you wallet is healthy enough to replace both, hell, go for it. Replace all four, it cant hurt. They will go bad sooner or later.

As for the shimmy, it sounds like your braking system was being activated by the EBTCM due to some false input or an EBTCM internal issue. When this happens, it WILL kick out the cruise control. (Its a logic thing). So, you shouldn't worry about the cruise control for now.

This happened to my 02 ZO6 and the EBTCM was the problem. Others have had the same issue and it was due to a faulty steering wheel position sensor. Some have had wiring issues.
The warming up message is telling you something. BLACK ZO6 has good info. Sometimes that message can be generated if the steering wheel is way off center due to a poor alignment or worn steering components.

When your going STRAIGHT down the road where there isn't too much road crown, is the steering wheel dead nuts centered or off to the left or right???

Bad wheel speed sensor/s normally throw a DTC and it will be specific for the bad wheel. You can have bad readings from a wheel speed sensor but the sensor can be FINE! Most of the wheel speed sensor issues that happen are due to faulty connections in the wiring harness. (the female connector pins are KNOWN to go bad and cause poor/intermittent connections. )

Your mechanic seems more familiar with your wallet than C5's.

BC

 

Hey Bill, Scotty, I've had similar problems with my stock '02 Vert. I've done a lot of research on this situation and found some other things to be considered. A couple of months ago I was out driving my Vert when the left rear wheel momentarily locked up, throwing me slightly askew but easily recoverable since I was cruising only 35 MPH on a smooth, straight, flat street. The DIC threw an immediate alert, "Service Active Handling". I also had the occasional "Active Handling System Warming Up" message but without any codes being thrown.

Anyway, when I got home after that latest incident, I retrieved the following codes:

1. 28 TCS C1284H (Traction Control System) Lateral Accelerometer Sensor Bias Malfunction.

2. 28 TCS C1285H (Traction Control System) Lateral Accelerometer Sensor Circuit Malfunction.

These are the same codes I had retrieved earlier after the DIC threw the alert, "Service Active Handling" while driving on the Interstate. On the advice of Forum members, I cleared the codes and continued to drive the car to see if the Active Handling alert would appear again. After this latest malfunction, I didn't drive it until the problem was fixed since I do a lot of Interstate driving at 65-75 MPH.

Since I replaced the LAS and cleared all codes, the car has been fault-free ever since.

Scotty, listen to Bill. Seems like he knows his stuff.

 

Once you are getting a solid error on a sensor, it makes it pretty easy to fix, and yeah ... I'd say Bill knows his stuff .... most people refer to him as the "electrical guru" around here : :

The EBCM (EBTCM as Bill calls it) uses the following sensors for the Active Handling software ....

* Steering Wheel Position Sensor (SWPS) located roughly at the base of the steering column - this tells the EBCM how far you have the steering wheel turned.

* Lateral Accelerometer ..... located in the vehicle cabin below left side of passenger seat - this tells the vehicle the lateral (sideways) G-forces that are being generated as the vehicle goes around a corner

* Yaw Rate Sensor .... located in the dashboard below the HVAC unit - this sensor reports the vehicles rate of "rotation" (yaw) as it goes around a corner

* Wheel Speed Sensors .... located in each wheel hub .... for the Active Handling function the EBCM uses the average speed from all 4 sensors to calculate vehicle speed. It does not use the Vehicle Speed Sensor as that may give a false reading if traction has been lost at the rear tires

Using data from these sensors, the EBCM can decide if the vehicle is oversteering or understeering. For example, let's look at understeer. Understeer is where we have turned the steering wheel but the vehicle is not turning as rapidly as it should. When the EBCM first sees the steering wheel turned a certain number of degrees, it immediately internally calculates, given current vehicle speed, what the yaw rate and lateral G-force should be. It then compares the calculated values to the values reportted by the sensors. In this example the values will be lower than calculated, so the EBCM will command the Brake Pressure Modulation Valve (BPMV) to generate brake pressure to the inside front brake to help "rotate" the car into the turn.

One reason I asked about the WARMING UP message is that when you start to see that appearing, that is another clue a sensor is going bad. The EBCM, everytime you start the engine, "calibrates" the SWPS. The EBCM waits until you are driving more than 6 MPH for at least ten seconds ... straight ahead, then calibrates the SWPS as being at "zero" degrees. How does it know you are going straight ahead if it hasn't calibrated the SWPS ???? Simple, the lateral accelerometer and yaw rate sensors are reporting zero and the wheel speed sensors are reportng over 6 MPH .... the car's going straight. BUT ... if one of the sensors (SWPS, yaw or lateral) are starting to report "noise" or bad data, the EBCM may not get that 10 second window, even though you're driving straight, so it reports the WARMING UP message to indicate it has been unable to calibrate the SWPS and AH is disabled until you see the WARMUP COMPLETE message.

So, if a sensor starts to report "bad" data, it is possible for the EBCM to react to that data when you don't expect it. The EBCM only recognizes a "failing" sensor when the sensor starts to send data that is "out of range" ..... such as the SWPS reporting that you just turned the steering wheel 5 full revolutions in a 10th of a second. Until the sensor gets "bad" you may see a few intermittent, momentary, activations of the AH system. Once the sensor goes out of range you will see SERVICE ACTIVE HANDLING on the DIC and a DTC will be waiting to point to the culprit sensor.

 

Stephen,
...Bill is the recognized electrical guru here but your posts are great and you do not always get the recognition he does. I pay very close attention when you OR Bill post anything about the technical stuff. Thanks to both of you for providing so much good help on these forums.
Jeff

 

Thank you, very much appreciated ......

Steve

 

The car drives perfectly, steers straight etc etc until the active handling kicked in and she gave me a tail shimmy for 1-2 secs. I do notice the active handling warming up every now and then.

To the mechanic's credit he did find one faulty wheel sensor and ended up fixing the problem for awhile. Now something else is going on. I just spoke with him and he is checking wiring connections.

Active handling seems almost not worth the trouble. Any way to just turn it off without having to push the button every time I get in the car?

 

No, there is no way to "turn it off" other than by pressing the button on the console.

As Bill said, the chances of your mechanic having found a failed wheel sensor are somewhere between slim and none. Most likely a connector was having a problem, or sometimes it can be things you'd never suspect .... got stainless steel brake lines on the car ??? One brand is infamous for causing "failed wheel sensor" diagnosis .... when it is the brake lines themselves that are the cause of the problem.

I'd recommend you continue to drive the vehicle until the sensor throws a code. It usually doesn't take long for the EBCM to see the problem. The good news is that you can easily replace yourself the sensors in the vahicle cabin. The SWPS is a little more work, but certainly doable for the "shade tree" mechanic.

I think you might be surprised at how good the Active Handling system is on the car. There are MANY stories on the forums of people who had their azz saved by the system. Get caught on a cold wet morning catching that unexpected puddle that kicks the rear of the car around and see what you think of the system after you're back in control of the car.

The electronics in these cars is getting so good, look at the best drivers in the world .... Formula1 ..... they have banned traction control this year from the cars because every driver wants it .... even a Michael Schumaker or Louis Hamilton wants it on their cars .... if they could have Active Handling ..... tunable for their style .... they'd want that too (it is also banned).

 

OK the mechanic was clueless, as you guys surmised. So I brought it home. guess I'll see if I can find the glitch.

Anyone have a list of all the active handling connection locations and suggestions as to how to clean them (as a start)?

 

Scottydog

Take a look at post ......

http://forums.corvetteforum.com/show...=speed+sensors

especially post #20 where Bill shows pictures of the wheel speed connectors (see 6th picture down) .... though it isn't time to go after those yet .... (I mainly wanted to get this documented in this post so I don't have to go search and find it again later .....)

The MAIN post you should look at (don't read the whole thing yet .... just page 1 will do fine) is Bill's EXCELLENT sticky at the top of this forum ....

http://forums.corvetteforum.com/showthread.php?t=896875

Read the first post about cleaning the elctrical grounds.

The grounds the EBCM uses are G103 and G108 (both in the engine compartment)

G103 is located on the right frame rail very near where the battery NEG cable is grounded to the frame.

G108 is located on the left frame rail almost directly opposite the EBCM

Seeing as we have no codes ... the best thing to do is inspect these grounds for corrosion. If in doubt clean them up.

Next step ... go out and ENJOY the car. If a sensor is gonna fail, driving the car will make it happen sooner rather than later. Watch out for the wind today .... I'm close to the bay and it has been howling around my house all night and (a little better) this morning.

Keep us posted .... we will find it .....

 

Well I pulled all the wheels, cleaned the wheel sensor connections, cleaned the two grounds behind the popups plus the main ground by the battery and the one by the ebcm. Didn't notice much corrosion.

Guess I'll drive it some and see if the cruise control keeps kicking out.

Thanks for the help guys!

 

Well that didn't fix the problem. I even yanked those stupid prong ground connectors and soldered in some eye connectors.

What should I do next?

 

Like I said before, just go enjoy driving the car ... I'm 90 percent confident that one of the 3 key sensors (SWPS, yaw, or lateral) is starting to get flakey. Driving the car will cause the sensor to eventually get bad enough for the EBCM to flag it with a DTC.

We could "throw parts" at this, but the issue is so intermittent (at least from your description) that, let's say for the sake of arguement you replace the SWPS right now ...... how "confident" would you feel that it was fixed ???

If you want to "throw parts" at it ... the SWPS is the likely culprit. I'd recommend against that though, the labor is pretty extensive (the steering column has to be semi-removed from the car) either for you to expend, or pay a mechanic for a "guess".

Just go enjoy the car (even if it is a kinda dismal day) .... drive it like you stole it ........

 

The "active handling" message is now popping up every 3-5 minutes or so. No more episodes of car seizures so far. I did get another "active handling warming up" message a few minutes ago.

How much is s SWPS? Anyone got a part number? If I can pull the dash to replace a HVAC actuator I guess I can drop the steering wheel.

I HATE driving a car with glitches...

 

The SWPS for a 2004 is GM part number 88965543.

GM list price is $76.07, but you can get it for about $50.00 from either ....

http://www.gmpartsdirect.com

or

http://www.gmpartshouse.com

or obviously your local dealer should have it, or be able to get it in a day or so.

I'll post again in a few minutes ... seems to me someone had a good write-up on the replacement ... let me see if I can find it for you ....

 

Take a look at this thread ... especially scroll down to post #15 where there are pictures and an explanation of replacing the SWPS.

IMPORTANT NOTES:

1) DO NOT let the steering wheel turn any significant amount once the steering column is disconnected from the steering rack. The steering wheel has a "clockspring" wiring arrangement for the horn and Airbag wires. If the steering wheel turns far enough it breaks the clockspring and your airbag and horn cease to work and you gotta pull the steering wheel to fix it.

2) DISCONNECT the battery and wait FIVE minutes before starting work on ANY of the wire connections to the steering column. This will ensure that you cannot accidentally fire the airbags.

Finally, if you're handy with a DMM (Digital Multi-meter .... voltage meter .... ) I can give you some instructions on testing the signal from the SWPS to see if we can verify it is the problem before you order/replace the part.

 

What thread are you referring to?

I would think accidentally firing the airbag would ruin your whole day!

I have a small digital voltage meter.

 

Damn ... I forgot to paste the URL in .... stupid ...... LOL ...

http://forums.corvetteforum.com/show...t=SWPS+replace

Again scoll down to 15 for pictures ..... next post DMM instructions .....

And yeah, firing the airbags, even assuming you aren't injured (or worse ... ) will cause at least $5,000 in damage when they go .... ONLY "safety" device in the history of mankind that the federal government requires a warning label for ..... how stupid is that ????