Unusual circumstances for 5E38 code?

T

tomjonesBT33

Member
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 be 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 US spec 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

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The tpms is not a seperate ecu. I strongly suspect the reason you are getting the light on for it is because of your 5E38 code. The car must be going in a straight line for the tpms system to work, and because it cannot determine this, the system (along with the DSC etc) is deactivated.

The tyre pressure is derived simply from the abs wheel speed sensors. If (in a straight line) one wheel is going at a slight different speed to the other, then it must be because it’s a slightly different diameter i.e low tyre pressure.

I notice you also have a power steering warning light on. Could it be a steering angle sensor issue that’s the cause (as this also brings on all the other lights you have).
 
Thanks for the reply.

I should have added a bit more. I have checked and filled the tires to the correct psi: 30 in front and 33 in back. I can connect to DSC and get to the RPA submenu with no problem. Should I be able to connect to the TPMS module under the INPA or ISTA separately? Again I get the IFH-0009 error if I try.

I also took real time readings of the steering angle sensor and it is working. I have not calibrated the sensor,e.g., to zero degrees. Can this / how is this done? I’m afraid to explore/use the Active sub menus because I don’t want to accidentally change anything on the ECUs.

I also notice that when the car is moving in a straight line the yaw sensor measures about - 4 deg (like I’m in a turn). I’d like to calibrate this sensor too if it’s possible.

Finally I notice the Ref U voltage fluctuates between 9.9V and zero. It’ll be 9.9v for a couple of seconds then quickly measure around 0V then back to 9.9v. I’m not sure if this is typical behavior for this measurement.

What other items could I look at with INPA/ISTA to help you help me?

Regards
Tom
 
Hmmm, you can’t calibrate the yaw sensor as far as I’m aware, I think the best you can do is just reset it in INPA at standstill. If you are sure your steering angle sensor is good I would probably be thinking about replacing the yaw sensor, it’s under the passenger seat in rhd vehicles. Sometimes they get wet which makes them go screwy... https://z4-forum.com/forum/viewtopic.php?f=3&t=117221&hilit=Yaw
 
One more thing, I believe the reason the EPS light is on is because I cannot connect to the ecu. I get the IFH-0009 error.

There was very brief time when I was able to connect and measure the torque sensor readings. I had thought that maybe I had a bad torque sensor which I understand is a common problem. Luckily I don’t think so. I think my EPS ecu is bad or the connection to the ECU is bad. Ive ordered another motor/ecu unit and plan to swap it out.
 
Well if you have a bad power steering ecu, this is likely the reason you have the other lights on too. So sort that first and see what happens.
 
If you suspect it's the steering angle sensor you can check out my thread:

https://z4-forum.com/forum/viewtopic.php?f=3&t=116884&p=1680732&hilit=Steering+angle#p1680732

A reset in INPA should be the first port of call since it's easy if you have it running.

I don't have access to my INPA right now but you can search for the menu you need to get to.

This should be it:

http://blog.obdii365.com/2015/02/03/reset-bmw-e46-steering-angle-sensor-with-inpa-cable/

After you press it, it'll be really quick and seem like nothing is happening and no other prompts. I just count to 10 (just incase) then exit the menu.

Next just go back into the live reading and verify it's been 0'd (obv don't touch the wheel until this part).
 
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