X5 E53 L1 - L4 Gear Fault Code - Trans Failsafe Prog

[dhelinski]

My X5 E53 2004 has been giving me the Trans Failsafe Prog message on occasion, and has gone into the limp-home mode (single drive gear engaged). The fault goes away after about 20 minutes w/ ignition off, and drives normally after. The issue started about 6 months ago, and has progressively become more frequent, to the point where it happens every day, multiple times a day. It happens while driving, after the vehicle has warmed up, and often while just driving along on the highway without touching anything (gear shifter, etc.). The fault code has been consistent - per the dealer it is an L1 - L4 GEAR fault. I've had the vehicle at an independent BMW shop to diagnose. Since the fault is temporary, they had issues troubleshooting the problem. They tried driving the vehicle with the diagnostic computer attached but could not get the fault to happen. That said, they did replace the seal/sleeve around the transmission electrical connector thinking that some leakage there may be causing the fault, but it did not fix the issue. I later took to the local BMW dealer - there assessment was similar - the fault could not be diagnosed directly because it would not remain active. They recommended replacing the gear shifter thinking it might be the switch causing the fault. I went ahead and replaced the gear shifter, and the fault still occurs. I am now at a loss of what to do next and how to further troubleshoot what might be causing the fault. I've researched the forums but could not find much regarding this fault - it does not appear to be very common. I understand the gear shifter is on a communication bus, and anything on that bus could trigger a fault - but not sure where to focus next. Comments/ideas would be appreciated.