This Cobb article may give some insight:
cobbtuning.atlassian.net
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Boost control code is entirely new on the Ascent due to the introduction of a fully electronic wastegate valve and air bypass valve on its FA24DIT motor....
...The starting commanded wastegate position is determined by the Wastegate Initial Position table (final boost target vs RPM) with compensations for baro, IAT, and initial position (this one is fairly redundant and the factory calibration is set to no comp). Wastegate position is represented in units of length (millimeters). The wastegate is more progressively open with higher values. This initial position is corrected by the turbo dynamics corrections based on boost error (described in next section). This commanded wastegate position ranges from 0 mm (full closed) to 15 mm (max. open) and is reflected in the Wastegate Position Commanded monitor.
The final commanded wastegate position (represented in the Wastegate Position Commanded Final monitor) is typically different than the initial commanded position described above due to a learning adjustment and ramping behavior:
When the commanded wastegate position is near 0 mm (i.e. request fully closed), the ECU enters a learning mode where the final commanded position is set to a fixed (low) position with a previous learning adjustment applied. The evaluation requires 1 second of time (where commanded position remains near 0 mm) after which the current (actual) wastegate position is sampled once and a learning adjustment is derived from this actual position vs. the theoretical fully closed position (0 mm). This difference becomes the new learning adjustment (shown in the Wastegate Position Learned Correction monitor) which is always added to the commanded position (with the total reflected in the Wastegate Position Commanded Final monitor).
If the commanded position is within 2.25 mm of the fully closed learned position, the ECU will slow the adoption of the commanded value by ramping down to it or, at times, hold the commanded value for a very brief period. This entire process occurs, typically, in less than half a second (at the start of a WOT pull for example).
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When the new turbo is installed, I wonder if they need to use SSM4 to reset the thing?