P08A0: Beta 2 gear-lever position must follow its calibrated path

P08A0 is the Y-position sensor 2 performance code in the reviewed GM shifter strategy. The controller names this input Beta 2. It can fail because the measured position falls outside the permitted shifter movement path or because percentage disagreement reaches the Beta calibration limit.

A mapped tolerance

The supporting Beta table gives percentage tolerances that vary with position, spanning 7% to 20%. These values describe a map, not a fixed 7% or 20% test for every possible lever location. Interpreting a trace requires the coordinates at which the comparison was made.

An outside-path event should also be distinguished from a disagreement event. The former concerns whether the indicated position belongs to the expected movement envelope. The latter concerns how far the compared values diverge. This separation can change what data needs to be captured on a repeat test.

Qualification and useful confirmation

The diagnostic requires calibration enablement and 10 failing samples within 12. Reporting is Type B across two trips. Since the page does not state the loop interval, it does not justify a precise failure duration in milliseconds.

A meaningful confirmation observes Beta 2 through the affected lever motion, with both path plausibility and mapped disagreement remaining acceptable. Merely clearing the code or checking one parked lever position does not demonstrate those results. This source is a monitor summary, not a component-isolation procedure; exact shifter applicability, signal representation and any repair decision need the vehicle's service information.

Source: GM monitor, PDF page 658; GM monitor, PDF page 1636.