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.

[upallnight]

Neutral safety switch is probably your problem. It would help if you gave some additional info other then it being an E53. There were three different type of trans in an E53 auto matic not counting the manual trans.

Here's a thread on the neutral safety switch.

http://www.xoutpost.com/bmw-sav-foru...ty-switch.html

[dhelinski]

The trans is a 6 speed steptronic in a 4.4i. Thanks for the link to the neutral safety thread (must have missed during first response) - will take a look at the inhibitor switch and see if that is what is at fault.

[dhelinski]

After checking under my X5 looks like my transmission is a later model that does not have the inhibitor switch. From realoem it lists the transmission part GA6HP26Z. Would appreciate any other ideas on the fault and what to focus on next.

Thanks!

[upallnight]

All modern day automatic transmission have a neutral safety switch. In your case the switch is located within the transmission. I replaced the neutral safety switch for an E34 and for an Audi A6.

The ZF 6HP26 trans is used in other car besides BMW.

Look at section 4.3 of this PDF file on the neutral safety switch for a ZF 6HP26 trans used in a Jaguar.

http://www.europeantransmissions.com.../6hp_trans.pdf