P03AA: Cylinder 3 pressure measurement fails a modeled-pressure check

P03AA identifies a cylinder 3 pressure-sensor function problem in Mazda's SKYACTIV-X engine. The controller is assessing the meaning of the pressure trace, not merely checking whether the circuit is connected.

Timing is part of the diagnosis

One trigger is measured pressure that differs from the value estimated using intake pressure and valve timing. Another is peak cylinder pressure occurring later than expected. A third compares pressure before and after top dead center and can identify reduced measurement sensitivity.

The monitor runs in a controlled fuel-cut region, with valid supporting sensor inputs and specific valve-control conditions. This is why the code cannot be used as a substitute for a mechanical compression test. The source itself includes inadequate compression among the possible causes alongside sensor and wiring faults.

Single-cylinder and wider patterns

Mazda checks the presence of other pressure-function DTCs and observes MAX_CYL_PRES data while examining connections. A number 3-only event provides a different fault pattern from several cylinders failing the same plausibility family. The procedure then separates supply, signal, ground and sensor inspection before the mechanical compression branch.

EGR and SPCCI are inhibited, combustion feedback stops and ignition timing is retarded. These are consequences of unavailable trustworthy pressure information. Confirmation requires the factory's relevant operating sequence and recurrence check. Preserve the complete set of pressure and fuel-system records before deciding whether cylinder 3 needs an electrical, sensor or mechanical repair.

Documented application

Mazda3 workshop manual 01/2019 onward, d9n1-1a-22d_ver10; PCM (SKYACTIV-X). Verify exact vehicle specification; this is a Mazda application example. Mazda factory diagnostic page, mirrored by CHARM.