Gas gauge off after 996 cluster swap

[ChrisZang]

I swapped my 986 for a 996 cluster some time ago and generally everything works (all indicator lights and gauges).

Except there's one small issue:
My cluster thinks the gas tank has a capacity of 20 gallons vs. the 16 gallons it really has. Yes, that means it came from a C4S convertible

I understand that I need a PIWIS to reprogram it.
What are the exact steps in PIWIS to change the capacity of the gas tank but w/o loosing any other features (like cruise control, computer, etc.)
Do I need to do any calibration afterwards?

Thanks

[Paul]

It can also be done with a PST-2. There is no setting for gallons, it is set by what car you select upon startup of the PST-2.


Here is the factory procedure after draining the fuel and adding 12L of fuel. The cluster in a 996 unit so all the operations take place under the 996 tab, it won't be recognized as a 986.

5. Perform tank calibration with the Porsche
System Tester 2.
- Select vehicle type (911 Carrera)
- Select control modules
- Select instrument cluster
- Select menu item Tank calibration
- Confirm calibration


The fuel level sensor system has now been
calibrated.

[ChrisZang]

Thanks Paul,

so how do I tell the cluster that it's in a 996 C2 instead of a C4?

[Paul]

Check PET and see if the gas level sensors are different part numbers for your car and a C4.

[pompous]

I've been wanting to swap to a 996 cluster for quite some time, but my miles would be off. I found a 996 cluster, but need to increase the miles on it. Is there any way to roll the miles forward?

[Paul]

No miles can only be adjusted in a almost new cluster.

[pompous]

Originally Posted by Paul

No miles can only be adjusted in a almost new cluster.

What happens when you sell the car then? That's gotta tank the value of the car I'd think.

[Paul]

You get a speedometer replacement statement from an authorized shop stating before and after mileage.

[ChrisZang]

Palo Alto Speedometer can adjust the mileage for $150

[Paul]

Interesting, my PST-2 will not do that after a certain number of miles have been accumulated. In regards to the fuel level, doing the calibration described above will cause the low fuel light to come on at the right time. I had the same issue with the 996 dash in my 98. Before I did the calibration the tank never showed full.

[ChrisZang]

@ Paul
The guys at Palo Alto Speedometer are a certified VDO repair shop, and I guess they have better ways to communicate with the brains of the cluster than the PST2 or the PIWIS. When you want the mileage adjusted they have you sign a paper, confirming that this is the actual mileage on the car.
In my case I increased the mileage by 40k+ miles, so that wasn't really an issue