Odd 5E38 error code

[tomjonesBT33]

Folks - I'm a new owner of a well used 2004 Z4 2.5i. It has a few issues that I've been trying to diagnose over the last couple of weeks. I have searched many forums including this one and haven't found my exact situation.

One issue that I've been unable to pin down is a fault code 5E38 'Defective rotation rate sensor.' From my research this could caused by a bad yaw sensor, lateral acceleration sensor (if they are separate sensors which isn't always the case) or bad wheel sensors. I have INPA and ISTA-D up and running and I've measured real time data from these and the sensors are working. When this error is triggered (which can happen at different times, speeds, etc) during my drive, I get the usual BRAKE and triangle with circular arrow. But I also get the TPMS light too.

In INPA I try connecting to the TPMS module and get a IFH-0009 Cannot connect error. I cannot connect to this module in ISTA either. In INPA I can get access to the RPA function with monitor run flat tire deflation. I can reset the TPMS error icon in the RPA menu. Since this is 2004, I'm not sure my car should have a TPMS Ecu since this was not mandated in the US until 2007 or 2008.

First question: does a 2004 Z4 have a TPMS ecu?

Second question: if so, would a 5E38 error result from a bad TPMS module

Third question: if no TPMS module, would a 5E38 error be a result of bad sensors in the tires?

Fourth question: where does the RPA function reside? Is it a separate unit or built into the DSC Mk60 unit?

Or is the TPMS error light a red herring and I need to look for another potential source

Thanks for any insights

[tomjonesBT33]

Want to follow-up and let the community know that the yaw sensor was bad (measured -7 deg when the car was sitting still). It's located on the passenger side floor in front of the seat. The carpet padding was soaked! And the module was very corroded. I found a used one from a mini cooper, swapped it out, and all is working with the DSC now.

Also, for new to early Z4 folks like myself, the 2003-2005 Z4s do not have TPMS. They use the wheel speed sensors to determine if one is "lagging" the others to infer that the tire may be flat. This error light was triggered as part of the yaw sensor issues.

[winnipegz4m]

Hey tomjones20194 - thank you for posting the question, and the answer!

[accent]

Ditto
Always great to learn something 'new' about our older Z4's. Thanks
Still love my 2003, 2.5 Do not want to trade it for anything newer