Car is a 2001 M6. Going down the highway my cruise shuts off on its own intermittently. I though I had a cruise control issue. One time I "caught" the culprit by observing the Active Handling in the DIC in the flash of an eye. Immediately after spotting the Active Handling message the "Cruise Disengaged" message comes on.

So, it's not a cruise issue it's the active handling kicking in which turns the cruise off as it should.

The active handling is kicking in for just a second when it shouldn't. It happens intermittently on a perfectly straight, smooth road independent of speed. No bumps, no chatter, no nothing. Some days I can drive over 100 miles without it happening and others it'll happen 3 or 4 times in a couple mile stretch. Very unpredictable.

I make the "problem" go away by turning off the active handling/traction control.

What do you think?

Rick

 

You could have a steering wheel position sensor or front end alignment problem.

Bill

 

Bill,

My steering wheel is off center a bit to the left. I would estimate 5 degrees. Do the sensors read from the actual steering wheel position? Could this be my problem? BTW, NO codes are thrown when this occurs.....

Rick

 

I also get the "Active Handling" message on the DIC when I am rolling up to a stop sign/light. It appears that my steering wheel is straight. I feel the brakes do the high frequency pulse when active handling is engaged. I also get the "Service Active Handling" and Service Traction Control". The codes I get are C1287 (wheel speed sensor(s)) and C1288 (steering wheel position sensor). I have read the service manual. Without buying a Tech II scan tool how do I determine if it is the wheel speed sensors or the steering wheel postion sensor.

I am not trying to hijack the thread. My issue very seems similar and relevant.

 

Those codes are both for the steering wheel position sensor....nothing to do with wheel speed sensors.

 

The sensor detects the position of the steering wheel. You do not always need a scan tool to narrow down the problem. If you look at the diagnostic procedure you will see there are some voltage measurements that are required. You can do those with a 10 Meg Ohm input impedance DMM. You may have to make up some jumper wires to make these measurements but they are within a home mechanic's capability.

There are a certain range of signals the EBCM will accept from the steering sensor. If the sensor is off due to alignment it may be closer to the limit than it normally would be. Depending on conditions you might get some erroneous activation and at other times get a code or you could get the activations quickly followed by a code. Whenever, you get a code the system is de-activated and the Service message is posted on the DIC.

Without looking at the codes it is difficult to know for sure what you should be looking at since the feature uses several sensors and the EBCM makes some calculations based on those sensor inputs. Here is the theory:
The vehicle stability enhancement system (VSES) is activated by the electronic brake control mdoule (EBCM) calculating the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.

The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error. The side slip rate error is a function of the lateral acceleration minus the product of the yaw rate and vehicle speed. The yaw rate error and side slip rate error are combined to produce the total delta velocity error. When the delta velocity error becomes too large and the VSES system activates, the drivers steering inputs combined with the differential braking will attempt to bring the delta velocity error toward zero.

So you have the steering sensor, yaw rate sensor, lateral g sensor involved in the EBCM's calculations.

One poster has 2 steering sensor codes so he should definitely check the sensor voltages and connections.

Bill

 

If your car's alignment is messed up ... that MAY cause SWPS errors.

Normally, when you first start the car and start to drive .... the EBCM is watching the yaw rate and lateral accelerometer sensors. When those are both reading ZERO ... that means the car is going straight down the road. The EBCM then measures the voltage from the two sides of the SWPS and says "OK .... those are the voltages when the wheel is making the car go straight ahead". Doesn't really matter (theoretically) if the wheel is canted 90 degrees ... the EBCM "locks into" the position that makes the car go straight. It then measures how many degrees you turn left ot right by watching the changing voltages from the SWPS.

If, after a period of time, the EBCM is unable to calibrate the SWPS, you will often see a message ACTIVE HANDLING WARMING UP on the DIC.

 

You are hijacking.

My issue has nothing to do with usage of the brakes. I don't have all the other DIC messages you have. I don't get any codes.

Not appreciated.

Rick

 

Bill,

Is this response to my issue or the guy who interjected his own problem?

I'm still wondering if the steering wheel being off center as I described is the potential culprit? Also, as I mentioned, I don't get any codes.

Rick

 

He wasn't hijacking, as you both likely have the same issue.

If your active handling is coming on during normal driving, then yes, your brakes are being applied (That's what AH does - applies braking to individual wheels).

Mine did the same thing, and in my case it was the steering wheel position sensor.

Sometimes it would just throw a code, and totally disable the AH/TC system...other times, it would err only enough to cause AH to engage and apply brakes (ie; on the freeway driving straight), but not err enough to throw the code.

If yours hasn't yet thrown a code, it probably will soon.
Until it does, it will be tough for anyone to say with certainty what problem sensor is causing it. The SWPS is by far the most common culprit though.

 

I guess this answers my question about steering wheel position. Basically, it's not a factor as a differential is measured as opposed to a static position.

Also, my alignment should be fine. Had it aligned several times in the past 3 months playing with different track settings. I've had no events which would have knocked it off, but something could have loosened and changed the setting.

What type of alignment issue could cause my problem?

Rick

 

Dude. take a

Apparently, you really don't understand the issue. Break loose with $150 and buy the service manuals. Reading is fundamental.

Good luck with your problems.

 

Thank you.

 

Thanks Bill,

I have a DMM. I run through the steps in the manual to check the output of the SWPS. The dealer wants $350 to change it. If I find it is bad, I will let them do it. I am not interested in R&R'ing the steering column.

 

An example ... and please forgive my use of NASCAR ... but it is the best example I can think of right now .....

In the last couple of weeks, I believe it was at Richmond, there was a camera placed above the track at the entry to turn one and looking down the front straight to the exit of turn four.

The cars would come out of turn 4, next to the wall, and come directly toward the camera down the straight.

Most cars looked "normal" but just a handful (DW pointed this out a couple of times) such as Kyle Busch's had a totally different "alignment". The body of the car, instead of being "square" to the wall as they came down the straight, had the rear body much closer to the wall than the front of the car. Even though the car was driving straight, the body looked like it was already turned into the next corner. The crews had intentionally "aligned" the car so the angle of the body in a corner could actually use air pressure on the side of the car to help it turn.

They had "aligned" the rear end (which you could do wth a Corvette) so that the LEFT REAR wheel was further forward than the RIGHT REAR wheel. For the driver to make the car go "straight" down the road he actually has to turn the steering wheel slightly to the RIGHT of center.

Now while an alignment like that may work great in NASCAR ... it is not good for the Corvette's Active Handling system. The yaw sensor would report that the vehicle was in "yaw" (the yaw sensor is aligned with the body) even when it was actually going "straight ahead" .....

Does this make sense ?????? Hard concept to describe .....

Basically Chevy programmed the system so that the body has to point "straight" down the road when the chassis is also going "straight".

If your alignment is off so the body is not "straight" when the chassis is .... the EBCM assumes your Steering Wheel Position Sensor is all balled up ....

Let me know if this has explained it .....

 

Understood. Thanks for taking the time to explain.

Rick

 

Actually it was an answer to both of you. I don't mind answering both questions as they are very similar. You still need to check your alignment and should check the SWPS. In this case unequal individual toe in from side to side would be the most likely cause of the steering wheel being off center. The calibration the system does is to account for wear in the steering and not an alignment problem. As for your problem showing up under braking that could be so. Braking will change the alignment slightly when you get front end dive. As the nose of the car goes down the negative camber increases which will increase toe in on a C5 since it has front steer Vs rear steer. Depending on how the toe was originally set that might just pull the alignment far enough out to trigger the things you have happening. Remember there is a tolerance band around the input/output of every electrical measurement device.

If the problem isn't alignment then the sensor could be going bad or could have some other issue. Has anybody been working in that area lately?

As for the accuracy of your alignment who has been doing the work and what spec's are they using? The spec's are written with a wide tolerance so anything from toe out to toe in can be OK. If you had somebody set up your alignment with several settings and paint marks for those settings on the cams/tie rods so you could change at the track the problem is the cams don't return to their original positions due to slop in the cam mechanism so you may not have the alignment you think you have.

Bill

 

I've got the same symptoms

The steering wheel is straight and the tire wear is even with no pull so I guess my alignment is fine.

I've tied it down to SWPS

 

Not to add fuel to the fire but... I do have this nice full gas can sitting here...

Symptoms:
Cruise shuts off, random braking on the interstate (REALLY not happy about that in the rain at 70-75), active handling comes on when slowing down during normal driving, active handling warming up message, and... (here's the icing) service active handling message.

History:
EBCM failed 3-4 years ago (man are these cars fun with no computer aids). Finally got around to replacing it last December. Noticed the above symptoms. Checked codes and got SWPS voltoage messages (one side high, the other low) ran out of time in the states and had to ship the car to England. Fast forward 5 months and I still have the same issues..

Cause:
Most likely a bad SWPS (all connections are good). Voltages do not move up and down as wheel is turned back and forth. They are random and fluctuate up and down on a given side while the wheel is moved steadily in one direction.

Solution:
Turn off active handling at start-up, reset "off" message in DIC for the time being, and smile because at least I have ABS again. Long term is to replace the SWPS when I get a chance (read as 3-4 years).

 

I agree. Would have to say, okay man, you win, your car is a lemon. Buy a new one. My 40 year old car doesn't have those problems.