P2564: turbo VGT SENT position input below its electrical range

P2564 is a low-circuit code for turbocharger boost-control position sensor A. This GM implementation specifically uses a SENT position sensor on a variable-geometry turbocharger. The monitored raw position representation fails below 1.00%.

Digital position is not boost pressure

The threshold describes the electrical input representation. It does not mean boost pressure is one percent too low or that the vanes are necessarily at their physical low stop. SENT signal health and position validity need to be interpreted through the installed system's service data.

The monitor requires calibration permission, completion of cranking and powertrain relay voltage above 11 V. Existing SENT out-of-range and performance fault states must be absent. The counter is 480 failures out of 600 samples on a 6.25 ms task, with Type A, one-trip reporting.

What to verify

Preserve the raw position input together with SENT status. A pressure reading or commanded vane position alone cannot establish this input-range fault. Likewise, another digital-signal fault may prevent this particular check from running and must be considered in the sequence.

After diagnosis, confirm that the qualified lower-range monitor completes with valid feedback. The summary does not identify a connector terminal, specify an analog voltage conversion or prove a mechanical turbocharger failure. Those decisions require the exact vehicle and actuator information.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1504.