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PCM change if change wheel size????


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The tire / wheel combinations that Porsche recommends all have the same outside diameter.

If the issue is with new tire pressure sensors, then that is available to update with the on-screen menus, not requiring a dealer visit.

What is changing, old parts and new parts?

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There is a coding option inside your PCM where it keeps track of your tire/wheel size. The nav system using a signal from your wheel speed sensors and the output would be erronous if you have different size tires than what your PCM is programmed for. I dont know the conversion rate from pounds to dollars, but your tech should be able to change this setting in less than 10 minutes.

Im not so sure about the tire/wheel combos all having the same outer diameter. If they did, why would you have to manually input that info in the menu for TPM or in the Nav?

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There is a coding option inside your PCM where it keeps track of your tire/wheel size.  The nav system using a signal from your wheel speed sensors and the output would be erronous if you have different size tires than what your PCM is programmed for.  I dont know the conversion rate from pounds to dollars, but your tech should be able to change this setting in less than 10 minutes.

Im not so sure about the tire/wheel combos all having the same outer diameter.  If they did, why would you have to manually input that info in the menu for TPM or in the Nav?

The usage of PCM in this instance is incorrect, it should instead be PSM.

The only related PSM calibration code I was able to locate was for the steering angle sensor. What menu or section has the tire / wheel size that is described?

Regarding updating the vehicle for new tire pressure sensors, each sensor has a unique ID code and the vehicle has to be "taught" the new codes whenever wheels are swapped.

Edited by wingless
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£210 is bout $400. ....To swap 4 wheels over!

I want to change 18" Turbos for 19" Cayenne Design. Dealer says that PCM settings need to be changed even if there are no TPMS? The rolling radius of the wheels is the same...just less tyre and more wheel.

What is the change is the PSM??

I only take delivery of my car on 1st march

Cheers

Matt

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£210 is bout $400. ....To swap 4 wheels over!

I want to change 18" Turbos for 19" Cayenne Design.  Dealer says that PCM settings need to be changed even if there are no TPMS?  The rolling radius of the wheels is the same...just less tyre and more wheel.

What is the change is the PSM??

I only take delivery of my car on 1st march

Cheers

Matt

There are no PSM, or PCM, changes to swap from 18" to 19" wheels.

The $400 charge sounds like an option upgrade charge, for the better wheels.

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There is a coding option inside your PCM where it keeps track of your tire/wheel size.  The nav system using a signal from your wheel speed sensors and the output would be erronous if you have different size tires than what your PCM is programmed for.  I dont know the conversion rate from pounds to dollars, but your tech should be able to change this setting in less than 10 minutes.

Im not so sure about the tire/wheel combos all having the same outer diameter.  If they did, why would you have to manually input that info in the menu for TPM or in the Nav?

The usage of PCM in this instance is incorrect, it should instead be PSM.

The only related PSM calibration code I was able to locate was for the steering angle sensor. What menu or section has the tire / wheel size that is described?

Regarding updating the vehicle for new tire pressure sensors, each sensor has a unique ID code and the vehicle has to be "taught" the new codes whenever wheels are swapped.

I can almost garauntee I remember seeing an option for this in the PCM2>>Navigation part of the tester. I could be wrong though. I will check tomorrow.

The Steering Angle Sensor security code has no relavence here.

About TPM, I wasnt saying the vehicle would need to be coded if a new sensor was used (if that was the case the vehicle would merely need to be driven). I was saying that those cars require you to select what size tire and wheel you're using.

The whole reason I brought up TPM was I was questioning the previous poster who said all the tire/wheel options for the Cayenne has the same outside diameter, which I dont believe to be true.

Edited by PTEC
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I didn't believe this at first but there is in fact a PCM option for Tire Change. It is under the NAVI SET options as described in section 8.12 of the PCM2 Manual. If you push the NAVI button and then the SET button you have several options including:

Tire Change

By selecting Tire Change using the rotary knob 16 the system is informed that the vehicle tires have been changed.

The query Reset calibration? is made.

The options Yes and No are available.

- Yes

Resets the calibration and starts recalibration.

- No

Recalibration is not started. The menu returns to Navigation Set.

(quoted from manual)

Recalibration? Recalibration of what?? Could it be the speedometer gets recalibrated based on GPS input? I am just guessing, but if that's true then I am truly amazed. If not, then who knows what this means?

Edited by 356driver
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