[anjuna]

Hi there,

Not an avid visitor of the X3 forums, as most of my expertise and hobbies are with the drivetrain of the F25 X3, which are most commonly shared and modified on the E90 N55 forums.

Vehicle - 2011 BMW F25 X3, xDrive 35i (3.0L N55) with 8 speed automatic (ZF 8HP45)

My vehicle has been meticulously maintained by myself. No long standing issues persist before I repair them. I've done standard maintenance, suspension replacement, brake replacement, transmission fluid changes... you name it and I've done it.

However, I have an issue that has come up recently without any major changes or maintenance corresponding with the issue.

I have received a slew of codes from, what I believe, is the ABS module:
1B0A21 - Rough Road Detection - No wheel RPM signal received

1B0A60 - Driving speed plausibility; Minimum speed under load implausible

1B0A61 - Driving speed plausibility; Minimum speed when in coasting / overrun mode implausible

1B0A62 - Driving speed plausibility; Speed signal implausible

1B0A64 - Driving speed, Wheel RPM sensor rear/left, signal change: not plausible

1B0A65 - Driving speed, Wheel RPM sensor front/left, signal change: not plausible

1B0A66 - Driving speed, Wheel RPM sensor rear/right, signal change: not plausible

1B0A67 - Driving speed, Wheel RPM sensor front/right, signal change: not plausible

I also get the following codes from the transmission, though I'm not sure it's an issue or more of a sanity check:

420611 - Transmission input-RPM sensor 2: Supply voltage outside of lower value range.

CF2F02 - Signal (actual speed of rear left/front left/rear right/front right wheel) invalid, transmitter DSC


Now, I think it's relatively safe to assume that I did not experience a simultaneous fault of every single wheel speed sensor, as every other case I've seen has had the first 3 or 4 codes listed, along with ONE wheel speed sensor. However, I am getting faults for all 4 wheel speed sensors.

Additionally, I get the whole lot of dash lights for vehicle stability, restraint system malfunction, "ABS - Brake System Drive Moderately," and the lot. If I start cruise control, it fails as expected, because the DME does not know the speed it is traveling. This is confirmed by evaluating the DME's vehicle speed, which remains at "0" throughout all driving.

The lights on the dash tend to cascade within the first few minutes of driving. I will start the car and it will alert me of a braking system malfunction and ABS system malfunction immediately. As I begin to drive, I will first lose power steering, then I will receive a "Restraint system malfunction" as well.

Then, the vehicle continues to drive "normally" after this point. No limp mode, no driveability issues, brake performance is normal (though, ABS does not function) and, other than the lights, warnings, and chimes, I do not experience any issues with the car's reliability or performance. The vehicle still makes ~19psi and all is well.

Oddly enough, I still receive an accurate vehicle speed on my cluster. I have noticed the following:
1. Intermittently, the speedometer will hang at 40mph, even though the vehicle speed is greater than 40mph, then suddenly rise to match the correct vehicle speed.
2. Intermittently, when coming to a stop, the brake pedal will push harder against my foot, as if there is a reduction in brake boost performance. The vehicle comes to a stop at the same speed and this does not appear to be a safety issue, but it's something worth noting.
3. The loss of power steering is rather odd, but given that it is EPS and not hydraulic, it would make sense that some speed related logic is not being passed to the EPS for assistance.

I have tried to disconnect the ABS unit entirely, assuming there may be a total fault there, but additional codes resulted (that I did not document), so the ABS unit must be passing some messages along canbus. Driving in this manner resulted in the same issues, but I had zero speedometer reading.

If I clear the codes, they come back immediately after driving.

I have not taken ISTA to the car yet, as I do not want to introduce more variables and changes into the situation, given that nothing has been changed since these problems have arisen.

tl;dr - I didn't make any changes to my vehicle, but now I have ABS/DSC codes, a christmas tree of a dashboard, MULTIPLE vehicle speed sensor implausible codes, and have no clue what a potential issue is for this poly-issue fault.

I would sincerely appreciate anyone's insight into the cause or a potential path to troubleshoot / remedy this issue.

[Wgosma]

Lots to deal with, a couple of thoughts to consider-

1) is the car's battery in good condition - as you know these cars can perform in odd ways when the battery is sub-par.

2) This may sound odd but I had it happen: the varments (rats I think) got to chewing on my electrical wires- I was getting a slew of odd codes quite randomly, after many attempts to solve this by resetting codes the car ended up with Mr. Mechanic....who found an intermittently shorted ground wire amongst a cable that had been munched on by the little intruders. Likely not your cause but food for thought.

Good Luck/Bill

[anjuna]

Originally Posted by Wgosma

Lots to deal with, a couple of thoughts to consider-

1) is the car's battery in good condition - as you know these cars can perform in odd ways when the battery is sub-par.

2) This may sound odd but I had it happen: the varments (rats I think) got to chewing on my electrical wires- I was getting a slew of odd codes quite randomly, after many attempts to solve this by resetting codes the car ended up with Mr. Mechanic....who found an intermittently shorted ground wire amongst a cable that had been munched on by the little intruders. Likely not your cause but food for thought.

Good Luck/Bill

It seems like it would be a lot to deal with here, but everything seems to be revolving around the DSC / ABS unit.

I think this because of the following
- ABS would fault if it doesn't know wheel speeds, explaining the first 3 codes.
- The four wheel speed sensors would all contribute to their individual codes, and the 4th code listed, which means it just can't determine vehicle speed.
- The second transmission code is just saying "Welp, the DSC isn't telling me the speed so idk wtf is going on"
- I think the first transmission code might be an expected pulse or signal fault from the DSC.

To address the two items you brought up...
Yes, I replaced the battery in / around January of this year. The battery I purchased was whatever the size is that's a step up from the original battery size. It still fit like a glove and I registered the battery at the correct Ah and have had no issues since then. Battery voltage is nominal when ignition is "on" as well as cranking and driving. I would expect to see a low battery voltage or high battery voltage.

Don't have many vermin around here, but I can't rule that out either. I would assume that, there may be one CANBUS wire that could be damaged. That was the reasoning behind me pulling the DSC connector completely to see if the behavior changed, and it did.

If it is some sort of grounded wire in the bundle or a single damaged wire, I'll report that back here.... when it's winter time. Right now it's a solid 105F outside in HTX and I'd rather die than spend hours troubleshooting it. That was part of the reason I wanted to reach out and see if anyone could provide insight of "yep, that exactly XYZ thing!"

But, given my own google-fu, I haven't come across a complete loss of wheel speeds like I mentioned here, so it may not be such an easy task.

Thanks for your help though - I'll see if I cant find an expected pin-out of the DSC unit and trace a few things back.... or go the lazy route and spend ~300 on an ABS/DSC unit off ebay

[Jg2420]

Hey I’m experiencing almost same exact issue. Did you ever find a fix

[anjuna]

Just sent a PM.

For public visibility, I ordered a new ABS pump and module, since all the wheel sensor signals come back to that module.

It's a bit cold out right now, but I will see if replacing the module and pump resolves the issue. The module could be replaced on its own, but disassembly / reassembly looks like a PITFA compared to moving some lines and bleeding.

Will update here once work is done and the results.

[Aspen235]

Any update?