P2302: Cylinder 1 ion-sensing circuit and secondary ignition diagnosis

P2302 is cataloged as ignition coil A secondary circuit. Mazda's SKYACTIV-G diagnostic page identifies the monitored function as the number 1 ion sensor circuit, associated with the ignition coil.

Start with the cylinder evidence

The PCM detects an erroneous ion-sensor signal after engine starting while speed is 2,000 rpm or less. The source includes cylinder 1 misfire as a possible cause and explicitly checks P0301 before proceeding through the ion-sensor electrical tests. A combustion fault can therefore change the diagnostic route; the secondary-circuit label is not sufficient proof that the coil assembly must be replaced.

The listed electrical paths include the sensor supply, ground and signal. Mazda checks the F8 15 A fuse, supply grounding or opens, an open ground, and signal shorts or an open. A damaged PCM connection is also considered.

What confirms the cause

An intact fuse alone does not prove that supply reaches the coil/sensor, and a good supply does not prove that its signal reaches the PCM. Those separate checks explain why the procedure reaches sensor inspection only after the circuit investigation.

Mazda lists no specific fail-safe on this page. Repair confirmation uses the engine-running self-test and a check for the same pending fault, which is more relevant than a key-on check alone for a signal evaluated after starting. Use the exact vehicle wiring and ignition precautions for component testing.

Documented application

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