Anyone knows where the temp sensor (RTC resistor) for the heated steering wheel resides? I can't seem to find any sensor on the wiring diagrams.. my assumption still is it is located inside the small steering wheel ECU..?!

Background: I'm in the process of retrofitting a heated steering wheel for my '17 Macan. Did the same process with another Macan earlier and it worked perfectly well after changing the ECUs of the steering column, steering wheel, and the wheel itself. Plus the small switch. Of course subsequent coding and inserting the activation code for heated steering... just like in a previous case.

Getting to the earlier questions above (temp thresholds): at least for 958 and 95B models the on/off thresholds in the ECU are set to -12 degree / +40 degree CELSIUS, thus the steering heater won't work beyond approx. 100 degree Fahrenheit. The target temp is set to +35 degree Celsius (whatever that means).

And yes - you can code the heated steering wheel to come on with the heated seats, this is a customer specific coding Piwis allows...

Now back to my issue - I seem to have a problem with the ACTUAL steering wheel temp as PIWIS FAP shows an error message for that value and I assume this is the reason why I can't get the heated steering wheel to work. I did not change the small steering ECU inside the wheel since we think it should be ok to use (it has the correct number already, and it connects the heater switch cable as well. We had to exchange it with an earlier Macan model, however, since it was an older version).

The error message reads as "Temperature Steering Wheel = RAW VALUE (VALUE_NOT_VALID):dad723dacf00fe00fe896463ce00"

But still - anyone have an indication if there is a separate RTC resistor (steering wheel temp sensor) somewhere outside the ECU? Or confirm my assumption that it is inside the ECU?

If not - I guess I need to try another ECU as final check.. I somehow need to get an ACTUAL wheel temp reading in order to make it work... if the ECU logic is ok of course the heating won't come on w/o an ACTUAL temp value

 

As far as my memory serves the NTC (negative temp. coëfficient) resistor is located near de temp switch in the steering wheel. It was replaced in my 2009 Boxster in March 2011. The resistor is connected in parallel with the switch. I don't have a wiring diagram and can't find one easily, so I can't confirm that you will find it in the schematics.
Hope that helps,
kind regards,
Joris Creyghton

 

Thanks Joris,

that definitely helps and you are right. I went through the pics of the steering wheel I bought and it shows a cable to the area of the switch, inside the wheel. This can only be for the sensor.. ;-) .. and it proves the wiring diagram wrong (strange but true).. the wiring diagram only shows the 2 cables for the switch in the connector to the ECU, plus 2 empty slots which are in fact occupied by the sensor in fact.

good to hear that one can replace that sensor - even though I don't find it in PET catalogue either. That gives me some confidence o get closer to the issue and solve it (before fall.. LoL)..

Cable colors as per wiring scheme should be black & black for the switch - but seem to be blue & white as one can see.. and one also can notice the sensor cables running along the lower left spoke into the wheel...

I know the wheel is from a recent 991, not a Macan originally, but don't suppose there's any issue with the cabling/sensor. Everything else fits and works perfectly..

I believe the sensor reading error goes back to the setup where there simply was no sensor and heated wheel, thus before retrofitting. Will try the following:

0. Check ports on cable vs wiring diagram (switch should be B1/B2, thus Sensor must be B3/B4 at ECU)
1. Reset the Steering Wheel ECU (there's a PIWIS option for that)
2. Check the sensor resistance value (not sure that leads anywhere if you don't know the resistors to-be values depending on temp)
3. Try other steering wheel ECU
4. Replace sensor

Great help! Thanks
Ray

 

..and to be complete - this is the connector at the steering wheel ECU where the sensor is connected but not included in the wiring scheme..:

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I did find a part of the wiring diagram on paper which is hardly readable, but it shows the combined button/NTC assembly (part no 997 613 425 00). I got it on paper from my dealer. If you want to see it I'm happy to scan it and send it to your email address (how?)

 

Thanks Joris,

some quick feedback to the entire community as I was able to figure some details out yesterday. Maybe it helps someone in the future resolving issues, ;-)

That was the plan:

0. Check ports on cable vs wiring diagram (switch should be B1/B2, thus Sensor must be B3/B4 at ECU)

1. Reset the Steering Wheel ECU (there's a PIWIS option for that)

2. Check the sensor resistance value (not sure that leads anywhere if you don't know the resistors to-be values depending on temp)

3. Try other steering wheel ECU

 

To share my resolution with the community:

Step #3 worked in my case. I changed the small steering wheel ECU (which seems to act as LIN slave to the steering column ECU) to a new one and voilá - my retrofit heated steering wheel is working now.

I can also see that the temperature gets recognized and is correct, and that the switch is also working (obviously). Thus,heat sensor NTC values (around 10kOhm @ 20 deg centigrade) seems to be correct and working.

I still have not figured out why my original ECU does not work with the heating though it carrys the samt part nr, same HW and SW version on the labels. I assume that the heating function was disabled at the time of assembly in the factory w/ a different flash.

 

Glad to hear that your heated steering wheel is now fully functional!
Your assumption abour a different flash must be correct.
Wish you nice warm hands in winter time :-).