Flashing DSC (4x4) Light on heavy acceleration.
 

Hi all,
I've been lurking as long as I've had my X5, but this is my first post. Back toward the end of last year, I purchased a 2004 E53 3.0i as a project car. The body and the engine were in pretty good shape, but she had been ridden hard and put up VERY wet for a number of years. I've just recently gotten enough done (thanks Covid ;)) to the vehicle that it was able to pass inspection, and get a license plate. I've been using it as my daily driver to shake the dust off and make sure there aren't any underlying problems that make it not worth the restore.

When driving at higher speeds (45mph+) if I stomp on the gas to gain a lot of speed --i.e. accelerating onto the freeway-- the DSC 4x4 light starts to flash, ABS activates, and it kills some but not all power from the engine. It's intermittent as to when this happens. It happens most of the time when on an on ramp, but sometimes it won't. When up to freeway speeds, it's fine and cruises great. Small to medium changes in throttle don't bother it.

I have both INPA and ISTA+ which I've been using to try and suss out this problem. It's not throwing any codes related to the VTG, and when driving while monitoring the wheel speed sensors, steering angle sensor and yaw sensor, all the levels seem fine and consistent with what the vehicle is doing at the moment. Transfer case fluid has been changed with the correct BMW fluid and the VTG adaptations have been reset. (The problem was there prior to the change and persisted after the change and adaptation reset). It also has a brand new battery and voltage looks great when running (13.9 - 14.3v)

So at this point I'm stumped. I can't figure out what might be making the DSC decide it needs to kick in. Anybody have any experience with an issue like this?

I hope you've enjoyed my novel ;), and thanks in advance for any suggestions or advice you might give.

Cheers.

The one time I had a similar situation it was the yaw sensor. What you might consider normal vs the computer could be entirely different things.

I would calibrate the yaw and transverse accelerometer (I forget BMWs name for it), I suspect that with long term idle period the calibration got lost. If you can graph the output do a before and after and hopefully the "after" is enough different the 4x4 doesn't kick on.

Does disabling the DSC prevent the behaviour?

Have you checked the transfer case gear (despite the lack of symptoms, i.e trifecta)?

I'll give that a shot here shortly, and report back. Thanks!

I haven't tried disabling the DSC yet because the problem is the DSC kicking in when it shouldn't. When it does turn on the DSC, it seems to be doing what it's supposed to do although with out any actual reason to engage. But I'll take it for a spin with the DSC off and see how it goes.

As for the transfer case gear, I've done a lot of youtube watching, for the symptoms and the sound it makes, and mine shows none of those symptoms. I have run the VTG actuator test from ISTA+ and it cycles what appears to be normal. Short of getting under there and pulling the motor/gear assembly to physically inspect it I'm confident it's working. But.... At some point here that's exactly what I'll do if nothing else seems to fix it. Thanks for the suggestions!

Are the tires all the same size?

Your car is telling you that a tire is spinning, that's the flashing light, and it shuts down throttle response and applies the brakes to the affected tire.

+1 on the tires. and the DSC is actually not "kicking in" when the light comes on it's telling you that it has reached it's limit to what it can do to keep stability.

jdstrickland,

The tires are in pairs, the front two are the same and the rear two are the same. the ones in the rear are Continental Crosscontact , and the Front are BFGoodrich, all the same size. The front are older and the rear are practically new. Based on monitoring the wheel speed sensors, and the fact that the 3.0 really doesn't have that much oomph, I'm 97% positive that no wheel is starting to spin. Again it doesn't do it when you floor it off of a dead stop, it's when the vehicle is already traveling 50mph or so, and I firmly accelerate (accelerating on an on ramp, passing on the highway). It does seem that the DSC system thinks a wheel is spinning, and is attempting to correct it. I'm going to double check all my tire pressures and reset the TPMS, incase that's giving faulty data to the DSC sys. Thanks for the suggestions!

That small difference may be enough to cause the DSC to trigger under acceleration.

On xDrive cars, it's best to change all four tyres at the same time...

Drove it today for a bit with the DSC turned off, and it behaves much more normally. Power when you need it, no sign of wheel spin or losing stability.

Swapped out the Yaw Sensor (Lateral acceleration sensor), pre drive the values in INPA look much the same as the old one. In fact the old sensor looks closer to 0.
The image with the lateral acceleration of .11 is the original sensor. I'm still researching if the sensor can be calibrated to 0 on a level surface via code. There's no option to calibrate it in ISTA+.

Thats good to know. The tires are legacy from the previous abuser ;) of the vehicle, and have been pretty far down on my list of things that need attention. I guess if nothing else become readily apparent as the cause of this issue, they'll have jumped to the top of the list.

are you able to get a snapshot of the values exactly when the car does it?

Test on a slippery surface like sand on gravel and see if you can reproduce the effect.

It’s actually pretty likely you are just getting wheel spin. Are you hitting the kickdown button at the limit of accelerator motion? If you are moseying around a curve in the typical situation of go under the bridge then left up the on ramp you’ll be in 4th. If you hit the kickdown the car will shift to second and the 3.0 can definitely break traction with old not awesome tires if there is just a little oily film from the cars before you.

I think you said you have x drive. Monitor the % to front. If the car is not putting enough torque to front, for sure, wheel spin.

They should definitely jump up on your list. Running mismatched tires like that front to rear can eat up your transfer case. There's a small difference allowed between the two, I don't remember how much, but it isn't much.

I looked it up once I think it’s 1% max s
Differential.

2225 / ∏ / 2 = 354 mm radius so 354*.01=3.54 mm difference in radius between tires

3.54/25.4=0.139*32=4.448

So, if the tires are the same model a difference of 4-1/2 32nd is what is allowed on the x-drive.

Different model tires can easily have more than that difference off the shelf.

To measure the radius of the tire I would lift the corner and wrap some masking tape (doesn't stretch) around and Mark where It overlaps then move to the other tire make another mark for the other axle.

My tires are 255/55/18 and are calculated to be 2225 or so mm = 2225/25.4=87.598 in.

That's roughly 87-5/8"

87.6*0.01=0.876 inch difference in circumference allowed or 7/8"

So get a measurement. People on xo have had their transmission act funny due to differential in tire sizes.

At least rule out tire size as the culprit (or discover it might be the problem).

I cannot believe that different brands of the same size tire is enough to confuse the system. If you have all 4 tires the same size, 265/75x18, whatever, then the car should be able to deal with any differences that come from manufacturing variations. My question about sizing was if the OP had tires that were actually different sizes, not different brands of the same size.

The system looks for all four tires to be rotating at the same speeds, but turning a corner demands that the outside tires turn faster than the inside -- the whole point of having a differential -- and if the tires front to rear are different sizes then the car is turning, the speed differences are accentuated and this might be enough to trigger the system activation. The flashing light means that the system is activated, the reported loss of power and the brake drag is a function of the activation of the system. All of the stuff reported is proper, except that the conditions are such that activation of the system is possibly not correct. All of the stuff reported is linked, and is doing what it is supposed to do. The problem is, it is doing it when it should be.

It's entirely plausible that the Steering Angle Sensor has lost it's home position, and the car is reacting to an extreme steering angle and a throttle position that is making the car fear for its life so it activated the Stability Control system. Before you do anything else, turn the steering wheel to full lock, then turn it to full lock in the other direction, then full lock again in the original direction. The computer will count pulses from lock to lock in order to know where home position is -- home will be straight ahead. You want to turn to full lock in a continuous motion without stopping.

Since purchasing my X5 new I have never replaced all four tires at the same time. I have almost always purchased two fronts or two rears at a time but there have been a few times when a tire couldn't be fixed that I purchased one tire when tread on remaining tire was about half of original depth. Never had a problem. From day one the rear tires have lasted less than half a long as the front.

We're on exactly the same page with that. The system is functioning exactly how it should, except possibly activating with no reason (bad data from one of the system inputs). I've calibrated my steering angle sensor with ISPA+, and swapped out the yaw sensor just to check. this morning I super carefully equalized all the tire pressures and reset the TPMS monitor (I'm not actually sure if the TPMS communicates with the DSC module but did it just to be safe). I'm about to head out and take it for a spin on the freeway. in answer to your earlier question all the tires are the same size 235/65-17.
I'll report back later with how it did.

Thanks again to everyone for all the input! You guys are awesome.

235s much more likely to lose traction. I have a feeling you just are breaking traction and DSC is just doing its job..

My X5 has 245/65x17. Andrewwynn might be onto something. If you're throwing the weight and balance to one side and hitting the gas hard, you can be spinning a tire and the DSC is doing it's job.

In the tire size numbers, 235 is the width of the tread. You have a skinny tire. You need to consider that you are driving in a manner that is causing the car to fear for its own life. It's not so important if you can cause the problem you report, it's important if you can avoid the problem you report.

I know this all too well.

I bought my x5 with 255/55/18 Dunlop winter tires.

I was immediately accustomed to the capability of the tire.

We bought wife's x5 with "bargain basement" 235/65/17.

When I drove her car in snow it felt like a bad front drive. I had no sense of all wheel traction. When I took corners like I always do in my car, her car would under steer over steer do anything but track a radius. It also just handled like total crap.

I bought a new/ish set of Dunlop winter tires for my car but also a new set of rims so I put my rims and tires on her car.

Holy crap it was absolutely night and day difference! I thought the handing difference had more to do with mine having the sport suspension.

In a blast from the past. The first car I drove as a teen was an Impala and it had 235s until one day dad found a deal on some barely used 225s.

The very first time I stopped firmly at a yellow light I probably should have gone through, obstacle like instantly locked the brakes; not even close to the same amount of force I used daily.

I'm a little surprised if the 6 is pulling off this feat but I think the odds are in the fairly likely class.

Fellas. I feel I may have given you the wrong impression when I mentioned "heavy acceleration" in the title of this thread. For the sake of clarity and hopefully finding a solution to my problem perhaps I should have said moderate.

I just finished replacing all the front end suspension components minus the shocks. Think tension arms, control arms, tie rods, sway bar links etc... It has been professionally aligned after that. The driving I'm talking about is me carefully function testing a project vehicle. I'm not out to break any land speed records here (That's what the Acura TLS is for ;)) I'm not even getting close to the kickdown portion of the gas pedal. We're looking at 4K to 4.5K RPMs tops, and straight on-ramps, not accelerating from 40 to 75 out of a corner or clover leaf. I've got a pretty good grasp on the physics of driving, and while I love a nice wide tire as much as the next man, wheel spin is wheel spin regardless of the tire size, and in my experience can be felt by the attentive driver. If I believed that the DSC was activating in situations that might even by a stretch of the imagination be getting close to the traction limits of the vehicle I would not waste your time.

At this point because I can't see any realtime errors with the sensors involved, I'm working on finding some software with which I can graph the sensor data over time to hopefully find the flaw in the system.

Once you are moving > 30 wheel spin impossible with the 3.0 even on snow not likely.

I've never had it happen going fast but when one of my wheel sensors was displaced about 1.0 mm it would make abs kick on every stop for about 8 stops before it would disable itself, so look at those as well.

They can be thrown off from rust or the rekuctor built into the bearing can fail producing the symptoms reported.

Comment on "butt sensor" for wheel spin. There have been plenty of times a wheel has lost traction that was impossible for the butt sensor to notice, because if three wheels still have traction there will be no untoward yaw for the butt to pick up.

When I say wheel spin I'm saying the car is going 35 and the wheel is going 36 not that it completely lost it donut burnout style.

Does the 4x4 light blink right at a short point or middle of a gear and at what speed?

If you can get some sensor snapshots of when it happens can be helpful.

One of us may be able to make a control run to see what is normal.

Do any other lights come on eg. abs/brake?

You guys need to wrap your heads around the fact that the DSC is "ON" all the time, the button turns it "Off" and when the light flashes it's signaling that the system as been overrun not that is "kicking in" or "activated". If there is something like a tire size problem that puts the DSC to the limit trying to compensate then it takes only a small difference to put it over the limit and turn the light on. Part of the job of the DSC is to eliminate wheel spin so saying that the light shouldn't be coming on because there is no wheel spin is kinda like a negative option chicken/egg scenario. If you better understand how it works it will easier to figure out the problem (most times ;) .)

Tentative success!
 

Looks like your first suggestion might have been right on the money. Finally got it out for a good drive after swapping in a replacement yaw sensor. 30 min, on and off the freeway, different rates of acceleration and problem appears gone. No flashing DSC light, no abs activating. I'll post back in a few days if the problem is really gone. Thanks again for helping me work through this!