[CoolATIGuy]

Troubleshooting a Gear Sensor code and Chassis Stabilization error

Specs:
- 2016 340 F30, xDrive, 6MT manual, M Sport, ~143,000 miles
- Pure 800 cast turbo (not the older core-charge version)
- SPEC Stage 3+ Clutch for single mass flywheel
- SPEC single mass Steel Flywheel
- BMS intake
- ctlss downpipe
- B58TU HPFP
- ProTuningFreaks Flex Fuel Kit
- All 6 NGK Spark Plugs replaced last summer
- All 6 ignition coils replaced last summer
- All 6 Bosch injectors replaced last summer
- Valve Cover replaced last summer with new OEM
- Lowered on H&R springs
- Michelin Pilot Sport All Season 4 tires and Slotted StopTech Brake Rotors, on all 4 corners
- MHD with David Shoup custom tune


I have an intermittent 1BC11F "Gear sensor, communication: Faulty" DME active code, that comes along with a Chassis Stabilization error. If you clear it, they always come back together at the same time. I've had this issue for ~3-4 months, first time was December 1st. They primarily come up under heavy acceleration, and will come up even if staying in one gear without shifting. Does not come up every pull, but also not infrequently

Here is the fault information I found: https://bmwfault.codes/XMLDiagView?d...IAOQAzADAANAA=

I also noticed when the code/error are thrown, the hill assist feature stops working, where it's supposed to hold the brake for a couple seconds on a hill so that you don't roll backwards when you switch to clutch/throttle. I'm guessing this is also related to the Gear sensor, because if the sensor has issues and doesn't know if it's in neutral or not, the hill assist probably wouldn't work, since hill assist is always off in neutral by default

I've also had a couple times where the automatic rev match acts up - instead of holding at a designated rpm like 3k for a few seconds during shifting like they're supposed to, the revs just dropped to around 2k rpm for half second, then fell right to idle. I believe that may have happened while the code/error were active as well. All of it seems to point to the car intermittently unsure if it's in neutral and getting confused

It sounds like from what I've read the auto start/stop can also be affected when the code is thrown, but I already have auto start/stop coded off by default, so I'm not sure on that


Apparently the gear sensor is on top of the transmission, and the harness can get unplugged sometimes when replacing the clutch. I would attribute it to that, however the clutch and flywheel I had replaced last summer, and I didn't start getting this code until December 1st (I had scanned it in MHD previously and my log shows I didn't have that code before)

At this point I feel like it's likely one of three things: either the gear sensor just needs to be re-adapted (it sounds like there is a way to do this in ISTA, but my BMW shop said they weren't able to locate the function in ISTA to do that?), or the connector/harness is partially unplugged/corroded/etc, or the gear sensor is faulty and just needs to be replaced


I haven't found a lot of talk on the forums about the gear sensor. Anyone have any knowledge to share? The sensor isn't too expensive (<$100), but it's not super easy to access. I also don't want to replace it if it just needs something like resetting adaptations for the gear sensor, maybe because it got out of calibration somehow. And I need to know if we do replace it, would the new Gear Sensor still require resetting/adapting within ISTA when installing it, or just plug it in and go? If it was related to the clutch/flywheel job though, I don't know why it wouldn't have shown up until 5 months later, unless maybe the harness was only partially plugged in and is coming loose?

I already double-checked with MHD, and they said you can't reset the gear sensor adaptations through MHD

I also have an MHD log from a 2nd gear pull (I didn't shift gears), where the code/error were thrown after I let off. I sent it to my tuner, he said the sampling rate was poor however the log itself doesn't show any torque limiters and appears to be working correctly from a tuning perspective

[CoolATIGuy]

We found the Teach-in gear sensor function in ISTA, and did that, as well as reset a few adaptations in MHD. Hasn't thrown the error since

[CoolATIGuy]

So far so good! Pulls like a freight train