Diagnostic article Generic OBD-II
P03B6: Cylinder 4 pressure input high despite the expected range
The documented Mazda P03B6 procedure covers cylinder 4 pressure input high despite the expected range.
Read before applying this article
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.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P03B6 reports cylinder 4 pressure-sensor circuit high input. Mazda's SKYACTIV-X PCM sets the electrical fault when the input remains above 4.84 V for five seconds.
High electrical input has two key wiring explanations
The source lists a signal short to power and an open sensor ground. The latter is easy to overlook if a high DTC is assumed to mean only excess voltage injected into the signal wire. Connector defects, the pressure sensor and the PCM are additional possible causes.
The factory flow also looks for P0398, P03A2 or P03AC on the other cylinders. Their presence redirects inspection toward the PCM connection. An isolated cylinder 4 event and several simultaneous high-input channels therefore support different starting points.
Use the separate tests for their intended purpose
Mazda checks the isolated sensor's connection and resistance, then the relevant signal and ground circuits and sensor function. A resistance result is not a substitute for verifying that the circuit can convey valid operating information.
The engine response disables EGR and SPCCI, stops combustion feedback and retards ignition timing. P03B6 does not prove excessive cylinder pressure or justify mechanical engine repair by itself. After correcting a supported cause, use the specified self-test and pending-code check while retaining any companion pressure-sensor records for comparison.
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.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
Cylinder 4 Pressure Sensor Circuit High
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT