Flashing DSC (4x4) Light on heavy acceleration.

[lichtman]

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.

[andrewwynn]

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.

[wpoll]

Does disabling the DSC prevent the behaviour?

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

[lichtman]

Originally Posted by andrewwynn

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.

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

[lichtman]

Originally Posted by wpoll

Does disabling the DSC prevent the behaviour?

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

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!

[jdstrickland]

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.

[80stech]

+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.

[lichtman]

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!

[wpoll]

Originally Posted by lichtman

… The front are older and the rear are practically new. ...

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...

[lichtman]

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+.